9th IAA Planetary Defense Conference 2025

A nuclear electric propulsion (NEP) vehicle concept and mission were developed for the 2025 Planetary Defense Conference (PDC) asteroid target. The work builds upon recent work by Brophy, et. al. using solar electric propulsion for planetary defense. The results with NEP are different given that the NEP vehicle’s power is not affected by distance from the sun. A relatively near-term NEP vehicle concept was developed the NASA Glenn Research Center Compass concurrent engineering team with the power system based on a currently planned 40 kW reactor system for the moon and internal studies to tighten the ion beam of the recently flown 7 kW NEXT ion propulsion system. The tightening of the ion beam allows for more momentum exchange ions to nudge the asteroid while also allowing the NEP vehicle to keep its distance from the asteroid. A recent 40 kW NEP vehicle designed for the moon will be modified to provide both the propulsion to get to the asteroid and then nudge it out of an Earth intercept.

To raise awareness of the potential threat that Near-Earth Objects (NEOs) might pose to life on Earth, the 2025 Planetary Defense Conference proposes a hypothetical asteroid impact scenario with the discovery of the “2024 PDC25” asteroid. To address this exercise, this work investigates different mission scenarios to conduct a spacecraft toward the asteroid and simulate an impact. Different launch dates are selected to investigate the optimal transfer, in terms of the increment of velocity (delta-V) requirements to complete the transfer, and to analyze how efficient earlier impacts might be in the deviation of the asteroid away from the Earth by the propagation of the ephemerids following the impact. To analyze and optimize the transfer, i.e. minimize the delta-V, a Genetic Algorithm (GA) is utilized considering a bi-impulsive maneuver between the Earth and 2024 PDC25 and the solution of Lambert’s Problem as the fitness function. Furthermore, different departures from the Earth-Moon system are considered. As time is of the essence, given the unknown nature of the asteroid, a direct departure in a hyperbolic trajectory is taken as a reference against a mission that utilizes a lunar gravity assist to provoke the departure of the spacecraft of the system, both with a single chemical impulse. Thus, the total cost of the mission, in terms of delta-V, is comprehended as the increment of velocity to leave the system plus the ones for the interplanetary transfer until the impact. It’s important to highlight that although the lunar gravity assist adds time to the duration of the mission, it reduces the costs of the mission, once a smaller delta-V is required to send a spacecraft to the Moon, where it accelerates to the outside of the system. In addition, this extra time required to perform the lunar gravity assist is considered in the analysis, as the effects of an earlier deviation are taken into account.

The destructive power of an NEO impact is closely tied to its mass. Especially in the period prior to or in the absence of a reconnaissance mission, an impactor mass must be determined using an estimated size, and it is this estimated size that is reported in official IAWN notifications and used by the international community to plan subsequent actions.

Currently, asteroid size estimates reported in IAWN notifications do not include consideration of the size-frequency distribution of the NEO population. However, it is well established that the number of NEOs exponentially increases with decreasing size, and accordingly that smaller impactors are more frequent than larger ones.

The PDC 2025 Hypothetical Asteroid Impact Scenario provides a useful case to illustrate the importance of including the NEO population size frequency distribution when considering the risk from a possible impact. The IAWN notification and Impact Risk Assessment Dashboard for the PDC 2025 hypothetical exercise gives:

• most likely 90-160 m diameter
• median of 126 m
• 5% of 75 m; 95% of 194 m

The reported probability distribution of diameters is consistent with a diameter measurement of roughly 126 ± 35 m (1 sigma), which would predict that a potential impactor with a diameter of ~90 m is about as likely as one of ~160 m diameter. Similarly, the estimate predicts that a potential impactor of 75 m is as likely as one of 194 m.

However, NEO size-frequency distribution models (Nesvorny et al. 2024, Harris and Chodas 2021) show that there are roughly 4 times as many NEOs between 90-100 m as between 160-170 m, and 12 times more NEOs of 75-m diameter as at 194 m. A simple convolution of the NEO size-frequency distribution and a Gaussian probability distribution for a diameter measurement of 126 ± 35 m (1 sigma) yields the following size estimate:

• most likely roughly 60-125 m diameter
• median diameter of ~90 m
• 5% of ~50 m; 95% of ~155 m

We note that the difference in volume between a 90-m and a 126-m object would lead to a roughly factor of 2 difference in mass, and that considering size-frequency-weighted probability distributions would likely lead to a lowered risk estimate. An analogous exercise can be done using H-magnitude size-frequency distribution, which would show similar results. We advocate for including the size-frequency distribution convolution in future size estimations provided in IAWN notifications, at least as an augmentation to the current size estimate information provided, to provide a fuller context for risk assessment.

Recent events and research have uncovered an additional potential contributor to global risk estimates from airburst and impact events, the Lamb-wave driven global tsunamis. The 2022 explosion of Hunga Tonga–Hunga Haʻapai (HTHH) generated a global Lamb wave that created tsunami waves in the oceans around the world where the water depth provided the conditions needed to create a Proudman resonance, where the velocity of the driving wave (Lamb wave) is close to that of the driven wave (tsunami). We have modeled Lamb-driven tsunamis for HTHH, as well as for the 1883 Krakatau eruption, that match the tsunami observations in terms of timing and amplitude. The simulations provided tsunami model verification and approximate Lamb wave scaling for variable explosion magnitudes. Given the scaling, our simulations have also demonstrated that, counterintuitively, explosions on land can also generate tsunamis. We have run scenarios for the Laacher See volcano, Tunguska airburst, Meteor Crater, and the 2023 PDC scenario with impacts in Dallas and Nigeria. All cases result in global tsunamis of various amplitudes.

For Epoch 1 of 2025 PDC, the risk corridor runs north-south from the Arctic to Antarctic, traversing Europe and Africa. One of the planetary defense data products is a graph of various components of damage (e.g. air blast, heat, etc.) as a function of location along the corridor. Most of the damage is caused by effects that decrease from distance from ground zero, so these graphs tend to strongly reflect the variation in population density along the corridor. By contrast, most of the damage from a global tsunami will be along coastlines that are nowhere near the impact point, even if it is on land. The variation in global damage as a function impact location is not intuitive because tsunami generation depends on ocean bathymetry, which dictates how strongly the Lamb wave couples as it moves along a great circle path. Tsunami run-up distances are a strongly non-linear function of impact location because the coupling and propagation are highly nonlocal and nonlinear. Our results will be compared with other components of the impact damage to assess contribution of this new potential impact.

The hypothetical asteroid threat exercise for the 2025 planetary defense conference includes an intriguing trajectory design challenge for possible deflection missions. The long (17 years) time span between the impact threat announcement and the possible impact date allows one to exploit multiple gravity assist (MGA) trajectories involving the inner solar system planets to allow an otherwise impossible low relative velocity rendezvous reconnaissance mission and, additionally, to improve the deflection performance of a kinetic impactor. In this work, we exploit a rapid Lambert-free sequence-independent trajectory finding algorithm [1] able to compute all possible MGA trajectories to the asteroid before the expected impact and select suitable reconnaissance and impact solutions among them. As expected, gravity assists are sine qua non for a feasible rendezvous with optimal phasing near perihelion. Additionally, the most promising solutions are characterized by multiple resonant legs. Interestingly, though, gravity assist impact trajectories (impacting almost tangentially and also near perihelion) appear to be more effective compared to direct ones for the proposed scenario. A rendezvous reconnaissance mission followed by a kinetic impact deflection mission appears to be technologically feasible with carefully designed MGA trajectories and multiple launch and arrival opportunities are available.

Reconnaissance missions are a crucial next step when a celestial body threat to our planet has been identified and confirmed to be significant. This helps in studying the body in detail by determining precise orbital characteristics and mapping the physical specifications, thus enabling the all the stakeholders to determine the best possible course of action along with the timelines. Multiple missions to the identified asteroid threat are possible, depending on the identification date and the time of impact. Flyby missions are the first option, followed by a rendezvous mission to extract vital insights.

The current paper proposes a rendezvous reconnaissance mission that would identify the physical, environmental and orbital characteristics of the asteroid threat and send these crucial details back to Earth, which would later help in the planning of a future deflection mission. The focus of the paper is primarily on the mission design and the development of the concept of operations (ConOps) of a spacecraft with multiple payloads for performing the reconnaissance and observation of the target asteroid.

The target asteroid for this paper is the hypothetical asteroid 2025 PDC. Mission planning is executed in stages when more information from terrestrial observations become available. For an initial guess of the spacecraft’s trajectory, porkchop or bacon plots with varying launch dates and impulse contours are used.

The design of the ConOps (Concept of Operations) includes detailing the different phases of the mission to fulfill the objectives as follows, in addition to the LEOP (Launch and Early Operation) and decommissioning phases:

1. Approach phase: wherein, the spacecraft is approaches within a threshold distance from the asteroid for initial data gathering.
2. The Preliminary Survey Phase: in which the spacecraft attempts to find and maintain a stable orbit around the asteroid.
3. The Detailed Survey phase: wherein precise orbit determination takes places and the physical characteristics of the asteroid are mapped to identify possible locations for deflection

In conclusion, the steps for an asteroid threat reconnaissance mission planning and the ConOps are outlined in order to create a framework that could be adapted to future missions.

This study examines whether the Kinetic Impactor, Nuclear Explosion or Laser Ablation could mitigate the impact threat of asteroid 2024 PDC25, a hypothetical asteroid with 17 years warning created for the 2025 IAA Planetary Defense Conference exercise. The potential impact date of asteroid 2024 PDC25 is April 24, 2041. Its absolute magnitude is estimated to be H = 21.9 ± 0.3 and the size estimate is highly uncertain. The deflection effectiveness of Kinetic Impactor, Nuclear Explosion and Laser Ablation are analyzed across four percentiles ($5^{th}$, $50^{th}$, $95^{th}$, $100^{th}$) of the asteroid's physical properties, considering both asteroid disruption conditions and varying launch performance. Simulation results suggest that a single Kinetic Impactor may be insufficient for deflection, while multiple Kinetic Impactors could achieve effective deflection without disrupting the asteroid. A single Nuclear Explosion can provide the sufficient deflection, however, the theoretical efficiency of nuclear-based approaches must be balanced with the difficulty in controlling the outcome of the explosion. Laser Ablation produces deflections comparable to a single Kinetic Impactor but offers a reduced risk of asteroid fragmentation, making it a notable advantage over impulsive mitigation strategies. The "Nuclear Cycler" concept, which proposes an incremental asteroid deflection strategy using multiple small nuclear explosions instead of a single large one, combines the high energy efficiency of nuclear methods with the precision and adaptability of slow-push strategies. This approach is applied to evaluate its deflection effectiveness on asteroid 2024 PDC25. This study provides insights and approaches on finding effective impulsive and slow-push mitigation options to address asteroid impact threats.

Near-Earth Objects (NEOs) represent a potential hazard to Earth, and effective planetary defense strategies are crucial for mitigating these risks. The Klet Observatory in the Czech Republic plays a pivotal role in both the research and public outreach related to NEOs. Since its establishment as an astrometric NEO follow-up station in 1992, and more recently with the deployment of the 1.06-m KLENOT Telescope in 2002, Klet has contributed significantly to international NEO research. In 2014, the Observatory became a partner in the European Space Agency's (ESA) Space Situational Awareness (SSA) programme, further enhancing its contributions to planetary defense efforts.
In addition to its scientific research, Klet Observatory has prioritised public education on NEOs and planetary defense. The outreach initiatives began with public lectures and have expanded to include a diverse array of communication channels. These efforts include specialised websites, open houses, social media engagement, educational multimedia presentations for schools, workshops for teachers, and geocaching events. The Observatory has also took part in TEDx talks, outdoor exhibitions, and activities for youth, with the goal of raising awareness about asteroid hazards and planetary defense strategies.
In the future, Klet plans to incorporate cutting-edge technologies such as virtual reality and STEM (Science, Technology, Engineering, and Mathematics) education to enhance public engagement. These initiatives are inspired by the concept of "Science & Art," aiming to make the complex field of planetary defense both accessible and appealing to the public.
Through over thirty years of experience, Klet Observatory has gained valuable insights into effective public outreach. The education of a broad audience—ranging from the general public and students to journalists and policymakers—on the risks posed by NEOs and the strategies for planetary defense has proven to be a crucial task for scientific institutions and researchers.
As a new feature of Klet NEO a Planetary defense we realised an excercise for public. This paper presents the results of a public exercise conducted during a hypothetical impact scenario involving the near-Earth asteroid 2025 KLET. The exercise aimed to engage participants in decision-making related to planetary defense, presenting a variety of defense options, including nuclear interventions, and exploring the role of evacuation strategies. The exercise’s primary goal was to enhance public understanding of NEO risks and promote awareness of potential defense strategies. The scenario was designed to engage both the general public and higher education students, encouraging critical evaluation of defense measures and their implications.
The design and methodology of the exercise, including the selection of defense options, criteria for public decision-making, and structure of the simulation, are discussed. Ultimately, Klet's mission also extends to inspiring the next generation of scientists and engineers, fostering a global, inclusive approach to scientific discovery, and emphasising the importance of international collaboration in addressing planetary defense challenges.

Asteroid search is a global effort for planetary defense. The International Astronomical Search Collaboration (IASC) is the leading global educational outreach program that provides astronomical datasets to citizen scientists to help asteroids discovery worldwide. Since 2021, the Ivorian Astronomy Association is involved in asteroid search endeavors. Two asteroids (2022 SW188 and 2023 TR26) have been discovered by the association. To increase the number of asteroid discoveries, the association has extended the asteroid search to secondary schools. Learning sessions have been organised to teach students how to search for asteroids. Around twenty students have been trained. The association intends to continue its efforts, because planetary defence concerns everyone.

Keywords: Communication, Asteroids, Comets, meteorites, Space Situational
Awareness

Sorvegliati Spaziali – Looking Up to Space to Protect Our Planet is a communication project by the Italian National Institute for Astrophysics, endorsed by NASA’s Planetary Defense Coordination Office Outreach Office. It represents one of the world's first coordinated, comprehensive, and coherent public awareness campaigns on planetary defense by a research institution. From near-Earth asteroids and comets to space weather, meteors, meteorites, and space debris, Sorvegliati Spaziali aims to provide scientific and cultural knowledge to illustrate how our planet is exposed to various natural and man-made space threats.
The core of the project is the entirely graphic and multimedia Italian website, sorvegliatispaziali.inaf.it, available online since 2021, where all communication products are published.

The project is at the forefront of using transversal, multidisciplinary, narrative science language and produces a variety of original multimedia information products, including news, videos, theatre videoclips, NEO, meteor shower and solar bulletins, a glossary, comics, and reviews.
One of its specific objectives was to develop a distinctive science brochure with augmented reality (AR) content on planetary defense, leveraging the significant potential of AR in modern science communication and public engagement.

The AR App Sorvegliati Spaziali is free and available for iOS and AR-compatible Android mobile devices (mobile phones and tablets), both in Italian and English and was developed in collaboration with the Italian company Vitruvio Virtual Reality.

It enables users to simulate four planetary defense phenomena in their environment, such as the entry and explosion of an asteroid into the Earth’s atmosphere, followed by a meteorite search on the ground. The brochure also provides in-depth content on events such as Tunguska and Chelyabinsk, along with updated information about the NEO population.

Here, we present the Sorvegliati Spaziali project and, in more detail, its AR app—an initiative that transcends mere edutainment by addressing critical issues such as risk perception and communication related to space events.

The damage from asteroid impacts is often measured in terms of areal extent and affected populations from the initial effects from blast waves, non-ionizing thermal radiation, and tsunamis (if the impact is over an ocean) [1-4]. We have considered the potential for additional effects, which could extend both to geographic areas affected and prolong risk to additional populations [5]. In addition, both initial and subsequent cascading hazards may have societal consequences beyond just the direct loss of life and property.

In this abstract, we suggest that supply chain disruption should be added to the list of possible societal (economic) consequences that are not necessarily fully captured by the metrics of affected populations or areal extent of damages from an asteroid impact. Supply chains form a complex network of production and distribution of goods and services. Identifying where supply chains are vulnerable, to local disruption from natural or man-made hazards, is important for maintaining resilience and can be applied to studies examining the consequences of asteroid impacts.

Visualization by [6] provides a qualitative way of identifying potential vulnerabilities from any hazard, including asteroid impacts. While the current version uses pre-COVID pandemic data, and the data resolution is only available by countries outside of the United States, the web application still provides a tool to access possible supply chain disruptions that could be part of pre-impact preparedness.

For the purposes of the IAA 9th Planetary Defense Conference hypothetical asteroid impact threat exercise scenario [7], preliminary analysis suggests the countries along the Epoch 1 risk corridor where an impact would have the greatest potential for supply chain disruptions are: South Africa (111B USD/yr), followed by Romania (82B USD/yr). Further analysis will be presented at the conference.

Acknowledgements and disclaimers:
Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

References
[1] Hills, J., & Goda, M. (1993) AJ 105(3), 1114–1144.
[2] Collins, G. S., Melosh, H. J., & Marcus, R. A. (2010) MPS 40(6), 817–840.
[3] Mathias, D. L., Wheeler, L. F., & Dotson, J. L. (2017) Icarus 289, 106–119.
[4] Rumpf, C. M., Lewis, H. G., & Atkinson, P. M. (2017) GRL 44(8), 3433–3440.
[5] Titus, T. et al. (2023) NH 116, 1355–1402.
[6] Ruddell, B.L., Miller, J., Rushforth, R.R., Salla, R., Soktoeva, E., and Gorantla, R. (2021), 'FEW-View™ 1.3, the FEWSION™ Visualization System', https://fewsion.us / www.fewview.us, 04 October 2021.
[7] Planetary Defense Conference Exercise (2025), Available at: "https://cneos.jpl.nasa.gov/pd/cs/pdc25/.

Since implementing the warning network systems for near-earth objects and bolide events, everything has changed for the safety of the planet [1, 2]. However, this has not been the case in the past, as
in the case in 1908 in Tunguska, Siberia, when an extraterrestrial object burned around 2150 km2 without any injury. Nowadays, the IAWN (International Asteroid Warning Network) is tasked with developing
a strategy using well-defined communication plans and protocols to assist governments in analyzing asteroid impact consequences and in planning mitigation responses.
In disaster management and impact response, there is a crucial fact to remark: More than a thousand people were injured because the sonic wave during the Chelyabinsk event collapsed the city’s
hospital system [3]. Today, in the world, there are around 50 cities with a population of more than 500,000. This work offers a training and education program for cities with populations exceeding 5,000,000
to cope with the likely repercussions of such catastrophes in heavily populated metropolitan areas.
Community awareness and avoidance of asteroid-related dangers are the aims of this program, which is based on earthquake preparedness standards. The risk of an impact is still low, but it’s not zero,
just like with earthquakes. Both catastrophes can seriously damage or destroy structures and people.
For example, a region’s tectonic setting affects the yearly risk of earthquakes, which may range from 0.01% to 1%. Similarly, bolide impacts cannot be foreseen, but we need to be prepared for the worst
because of how dreadful they may be. The training program focuses on teaching people to detect early warning signals of an explosion or atmospheric impact, such as a blinding flash of light, and to take
timely action to reduce injury. Important things to remember include staying away from windows to avoid being harmed by broken glass, finding a safe place to hide to decrease the risks of hearing loss
and debris hits, and following evacuation instructions to the letter. Like in earthquake-prone countries, this project attempts to educate citizens to establish a resilience culture that will help minimize the
impacts of these uncommon but high-impact events. In calling attention to the parallels between NEO impacts and earthquakes: low probability, high impact hazards, this research underlines the necessity
to integrate asteroid impact preparation into urban disaster response strategies. Through education, metropolitan centers may greatly strengthen public safety and raise their ability to respond effectively to foreign hazards, and therefore not generate dread in society.
References
[1] G.-R. S. D. Book, Goes-r series data book cdrl pm-14 rev a. may 2019, noaa-nasa, 2019.
[2] P. Jenniskens, J. Albers, C. E. Tillier, S. F. Edgington, R. S. Longenbaugh, S. J. Goodman, S. D. Rudlosky, A. R. Hildebrand,
L. Hanton, F. Ciceri, et al., Detection of meteoroid impacts by the geostationary lightning mapper on the goes-16 satellite,
Meteoritics & Planetary Science 53 (2018) 2445–2469.
[3] A. E. Dudorov, D. D. Badyukov, S. N. Zamozdra, N. N. Gorkavyi, O. V. Eretnova, S. A. Khaibrakhmanov, A. E. Mayer,
S. Taskaev, Meteoroid, bolide and meteorite Chelyabinsk, in: Materials Science Forum, volume 845, Trans Tech Publ,
pp. 273–284

Keywords: Risk perception, public awareness, near-Earth objects, research design, emergency management

Near-Earth Objects (NEOs) are a low probability-high consequence hazard with potentially catastrophic impacts. The Chelyabinsk impact in 2014 and recent technological advancements such as the Double Asteroid Redirect Test have brought planetary defense to the fore. There is, however, limited research that addresses perception of NEO risk, meaning that preparedness initiatives are based on differing understanding of the risks faced, which compromises response efficacy. Preparedness begins at the local level and requires a global collaborative effort as the impacts of a NEO strike could overwhelm community lifelines, infrastructure, and local capabilities. The aim of this proposed study is, therefore, to critically evaluate how the public, emergency managers, and NEO subject matter experts perceive the risk of NEOs.

The proposed study is informed by an inductive system of logic, social construction philosophy, web-based self-completed questionnaires, semi-structured interviews, and qualitative content analysis methodology. First, members of the public will be snowball sampled to participate in a web-based self-completed questionnaire relating to their knowledge, perception, and conceptualization of NEO risk. Second, local and state-level emergency managers and NEO subject matter experts will be snowball sampled for semi-structured interviews relating to their knowledge, perception, and conceptualization of NEO risk. Third, the resultant data will be analyzed using computer-assisted qualitative content analysis to determine differences in NEO risk perception and knowledge between the three participant groups.

This proposed study will highlight the differences between the general public, emergency managers, and NEO subject matter experts. For example what is not being properly communicated to the public about NEOs? What are the publics’ misconceptions about the threat of NEOs? What information do local emergency managers want to know to increase NEO preparedness for their communities? Results from this study will help to bridge the gap between scientific experts and localized communities to enhance planetary defense.

The OSIRIS-APEX (Origins, Spectral Interpretation, Resource Identification, and Security–Apophis Explorer) mission will approach and rendezvous with asteroid (99942) Apophis in the spring of 2029, just after its close approach to Earth (DellaGiustina et al., 2023). APEX has three primary mission goals. The first is to study the processes that drive the evolution of small asteroids, including tidal effects from close encounters with terrestrial planets. Apophis will come within 0.1 lunar distances of Earth (Farnocchia & Chodas, 2021). This encounter is expected to result in potentially dramatic tidal deformation (Dotson et al., 2022). Additionally, APEX proximity operations will help to reveal changes in the rotation state. Indeed, by comparing the spin states of Apophis before and after Earth close-approach, APEX will be able to constrain the internal density distribution, an important property needed to inform impact threat assessments (NASA, 2023).

The second goal is to determine the characteristics of a “stony” (S-complex) object to study physical and dynamical evolution, including any previous Earth encounters. The mission will obtain images across a broad range of wavelengths (0.4–100 µm) and lidar ranging data to produce meter-scale maps and centimeter-scale global morphology. Radio science will be used to determine the mass of Apophis and the degree-2 gravity field, providing information about mass, interior structure, and surface properties. Taken together, these measurements will constrain the mechanical structure of Apophis including surface heterogeneities – key properties that help inform planetary defense strategies (NASA, 2023).

The third goal is to examine the properties of a potentially hazardous S-complex asteroid to help inform planetary defense knowledge and strategies. APEX will measure the near-surface strength of Apophis through the Spacecraft Thruster Investigation of Regolith (STIR) maneuver. The spacecraft will approach Apophis’s surface, then back away using its thrusters, which will excavate material. The response of the surface will provide constraints on material strength, porosity, and bulk density — key properties controlling momentum transfer efficiency for a kinetic deflection mission (Stickle et al., 2022).

Additionally, the rare close encounter of Apophis with Earth will provide excellent viewing conditions for many ground-based observatories. Comparing in situ rendezvous data from APEX with ground-based observations will enable synergistic analysis and calibration of datasets and improved higher-order science products. In particular, data returned by APEX will help to assess the accuracy of ground-based measurements of properties relevant to planetary defense. Thus, the Apophis close encounter and APEX mission present the opportunity for a globally coordinated planetary defense exercise using both ground- and space-based assets (Barbee et
al., 2021).

• Barbee, B. et al. (2021) BAAS, doi:10.3847/25c2cfeb.dc0c7b69.
• DellaGiustina, D. N. et al. (2023) Planet. Sci. J. 4, 198.
• Dotson, J.L. et al. (2022) Apophis Specific Action Team Report. SBAG, LPI.
• Farnocchia, D. and Chodas, P. W. (2021) Res. Notes AAS 5, 257.
• NASA Planetary Defense Strategy & Action Plan Working Group (2023),
  NASA Planetary Defense Strategy and Action Plan,
  https://go.nasa.gov/3UO2mmt
• Stickle, A. M. et al. (2022), Planet. Sci. J.
  3, 248.

Keywords: Apophis, OSIRIS-APEX

The OSIRIS-APEX mission will repurpose the OSIRIS-REx spacecraft to study Apophis, rendezvousing shortly after the asteroid’s close approach to Earth on 13 April 2029 [1-3]. The mission will produce and release many data products. We highlight here some that will be of particular interest to the planetary defense community.

• Shape model: We expect to produce a global shape model at 25 cm horizontal spacing or better, with vertical precision of a few centimeters.
• Mass and gravity field: We expect to measure the mass to better than 1% accuracy and the gravity to 2nd degree and order terms. At Bennu, the target asteroid of the previous mission, the orbits of particles that had spontaneously ejected from the surface were used to probe the gravity field to higher terms [4,5]. Thus, if ejected particles also orbit Apophis, the gravity field estimate will likely be better.
• Density of near-surface material: By observing the response of surface material to the spacecraft’s maneuvering thrusters, we will likely be able to estimate the mechanical properties. In addition, APEX maps of surface wasting features may constrain material strength and density.
• Thermal properties: APEX will observe the infrared spectrum of Apophis from a wide variety of viewing directions (times of day and night). These data will be used to map thermal inertia of the surface and to compare with ground-based observations.
• Yarkovsky acceleration: The Yarkovsky acceleration of Apophis has been measured using extensive ground-based radar and stellar occultation observations [6]. The close Earth encounter will change the Yarkovsky acceleration, as it changes the orbit and rotation state. APEX will re-measure the Yarkovsky acceleration to an accuracy of 4% of its current value in the planned campaign, or to 0.1% if observations can be extended an additional 4 months. This accuracy likely will not be possible from ground-based measurements until 2050. The updated Yarkovsky measurement will allow us to test models of the physical process, as well as improve our knowledge of the orbit of Apophis.
• APEX will produce spectral maps to understand surface heterogeneity.

References.
[1] DellaGiustina, D. N. et al. (2023) Planet. Sci. J. 4, 198. [doi:10.3847/PSJ/acf75e\
[2] Roberts, J. H. et al. (this meeting).
[3] Polit, A. T. et al. (this meeting).
[4] Hergenrother, C. W. et al. (2020) JGR Planets 125, e2020JE006381. doi:10.1029/2020JE006381
[5] Chesley, S. R. et al. (2020) JGR Planets 125, e2019JE006363. doi:10.1029/2019JE006363
[6] Farnocchia, D. and Chesley, S. R. (2022) Apophis T-7 Years workshop, abstract #2007.
https://ui.adsabs.harvard.edu/abs/2022LPICo2681.2007F

Keywords: Dimorphos, Apophis, HERA, RAMSES

CNES contributes to the most essential Planetary Missions of this decade, aimed to the binary asteroid (65803) Didymos, and to the asteroid (99942) Apophis. We start with the Hera mission launched by ESA on October 7th 2024. Its target, Dimorphos, the 151 meters moon of Didymos, was successfully impacted by NASA's DART proe on September 26th 2022. Hera now aims to observe the effects of this impact in situ and study the binary asteroid’s geophysical characteristics.

Hera combines a mother-spacecraft, with five instruments, and two Cubesats, Juventas and Milani. Hera will conduct the first ever radar survey of an asteroid’s interior with the JuRa mono-static radar on Juventas, which has a French Principal Investigator from IPAG. The mothership will be controlled from ESOC in Darmstadt, Germany, and the two cubesats from ESEC in Redu, Belgium. CNES, in Toulouse, is in charge of proximity operations for the cubesats, including trajectory control and instrument planning, from their separation from Hera to asteroid landings.

Apophis is also an exceptional target on the occasion of its Earth approach at a distance of 31 000 km on April 13th 2029. This will be a once-in-millennium opportunity to address two primary goals:

• Find out how much such a close planetary encounter causes changes in some of the physical and dynamical properties of an asteroid,
• Understand the interior structure of a small and likely rubble pile asteroid and draw implications for its formation, evolution and response to a deflection attempt.

CNES has been working since 2022 with JPL on the Caltech mission to characterize Apophis (to be presented by Carol Raymond from JPL at this PDC), based on three spacecraft: a mother-ship, and two CubeSats equipped with a bi-static radar derived from JuRa mentioned above. At this stage, CNES is considering to contribute to the radar, and to provide the ISL S-band equipment installed on all three spacecraft which
will synchronize the CubeSat clocks through a loop with the mothership to achieve accurate bi-static radar measurements.

ESA has also initiated the development of RAMSES, that will launch towards the end of April 2028 and reach Apophis two months before its Earth's close encounter.

RAMSES benefits from a strong HERA heritage and is based on the same
architecture, with a mothership and two cubesats. It will characterize Apophis with high-resolution before and after the encounter. CNES is considering to participate to RAMSES’ cubesat operations, and to the investigation of Apophis internal structure with a contribution to a monostatic tomography radar similar to JuRa, with a seismometer based on geophone technology to be provided by ISAE, and possibly with a near infra-red camera. In addition, CNES is studying a fly-by probe equipped
with visible cameras that would share RAMSES’ launcher. This would be a very valuable Planetary Defense demonstration where a potentially threatening asteroid would be observed through a fly-by, and those results could be confronted a few weeks later to the extensive characterization obtained by Caltech mission to Apophis, RAMSES, and Osiris-Apex.

The thermal infrared imager TIRI was developed for the ESA Hera mission, which was launched on 7 October 2024 by the SpaceX Falcon9 launch vehicle from the Cape Canaveral Space Force Station. Hera will rendezvous with the S-type near-Earth asteroid binary 65803 Didymos and its moon Dimorphos in December 2026, and perform a six-month-long observations there for the purposes of planetary defense and planetary science. The asteroid binary has been imaged from the NASA Double-Asteroid Redirection Test (DART) spacecraft on 26 September 2022, just before its kinetic impact to Dimorphos, so that the hemispherical features of both asteroids and the up-close local surface features of Dimorphos were observed. The ground-based observations showed that the orbit of Dimorphos around Didymos was successfully deflected by the DART impact, but its efficiency remains uncertain because we do not know some key parameters such as the mass, internal structure, cohesion, orbital and rotational motion of the asteroid, the amount of ejecta by DART impact, as well as the surface properties like porosity, strength and geologic features. Most of these parameters are expected to be investigated by Hera.
TIRI is the successor of the TIR on Hayabusa2 (Okada et al. 2017), and based on an uncooled micro-bolometer array (Lynred PICO1024 Gen2) with 1024 x 768 pixels, and covers the FOV of 13° x 10°. TIRI has an 8-position filter wheel, with one wide band at 8-14 µm for thermographic imaging and six narrow bands centered at 7.8, 8.6, 9.6, 10.6, 11.0, and 13.0 µm to characterize composition, crystallinity, or degree of thermal alteration of the surface materials. TIRI will be used to investigate thermophysical properties of Didymos, for the first time as an S-type asteroid, and map physical and compositional properties of Didymos which has relatively flat area at the equatorial regions and rugged regions at the higher latitude regions. TIRI will be also used to study thermophysical properties and surface materials of Dimorphos, including the remnant crop after the DART impact, whether there is an excavated crater or a completely deformed feature. Up-close DART images indicate that Dimorphos is a rubble pile body but we do not know whether the surface boulders are porous or consolidated, and whether its composition is similar to Didymos or not.
The initial in-flight checkout operations just after the Hera launch show that TIRI is healthy and performs well as was shown in the Earth-Moon images. Observations of the Mars and its moons, Deimos and Phobos, are being planned during the Mars Swing By in March 2025, to be used mainly for the in-flight calibration of the instrument, and hopefully for scientific study of the opposite side of Deimos to Mars. The flight spare of TIRI will be provided for the Rapid Asteroid Mission for SpacE Safety (RAMSES) mission led by ESA, to observe the surface thermophysical properties and constituent materials of the S-type Near-Earth asteroid 99942 Apophis before, during, and after its close encounter to the Earth on 13 April 2029.

Satis is an ESA planetary defence mission study. The mission consists of a stand-alone 12U-XL CubeSat that aims to rendezvous with a Near-Earth Object (NEO). Satis serves as pioneer to demonstrate a completely new class of small, fast-response missions for planetary defense. Here, we present the Satis mission and its science and planetary defence objectives.

The main objectives of the mission is to characterize a NEO closely. The interior structure of such an asteroid carries the imprint of its collisional and accretion history and is important for planetary defense mitigation attempts and Hypothetical impact assessment [1]. Satis aims to perform detailed characterization of basic physical parameters relevant to planetary defence; interior structure, surface properties and the dynamical state.

The feasibility of the Satis mission concept was studied by an ESA CDF study [2] and since then the mission and system design further advanced [3]. The mission concept is built on a stand- alone CubeSat. The mission starts on a dedicated micro-launcher equipped with a kick stage. The kick stage will be used to inject the CubeSat onto the required escape velocity vector. Following commissioning, the CubeSat will use a high-performance miniaturized electric propulsion system for the interplanetary transfer to achieve the rendezvous with Apophis. The mission duration will cover operations close to the asteroid up to six months. Proximity operations will lead the spacecraft very close to enable detailed analysis of the asteroid. Communication and navigation will be performed using a miniaturized X-band transponder interfacing with ESTRACK deep space ground stations. The payloads considered include a visual camera, thermal imager, radio science experiment as well as Hyperspectral, VIS/NIR imagers to fulfil the science objectives.

Satis Phase A study including Mission Definition and Preliminary Requirements Reviews was successfully completed in the last quarter of 2024 and the Phase B will start in 2025. The target of Phase A study, Apophis encounter with Earth would enable the direct observation of changes in the asteroid’s rotation, possible surface changes, as well as its long-term orbit. Satis would observe these parameters to assess the effects of an Earth close encounter to better characterize the NEO and the evolution of asteroids. During the Phase B study, a fast NEO characterization mission will be considered also without a close encounter and alternative targets, especially other Potentially Hazardous Asteroids (PHA) [4]. The preliminary study identified few hundred potential targets compatible with the Satis mission launch and orbital parameters from the Minor Planet Center database. During the phase B Study these potential targets will be further studied along the mission and payload studies.

References: [1] Senel C. and Karatekin Ö. 8th IAA Planetary Defence Conference, 3-7 April, 2003, Vienna. [2] Satis CDF study (2022) ESA-TECSYE-HO-2022-003030. [3] Fogliano, V. et al. (2024) Small Satellites Systems and Services (4S) Symposium, 27-31 May, 2024, Palma de Mallorca. [4] Karatekin, Ö. et al. (2024) Europlanet Science Congress 2024 Vol. 17, EPSC2024-249.

PDC2025
Stellenbosch, Cape town, South Africa

Conference Topic: NEO Characterization (or Public Education and Communication)

Towards angular and rotation tracking of Apophis with Meade telescope in 2029: Citizen science tracking ISS and presenting on public education site

Aron Wolf Siegel(1), Hugo de Jong(2), and Nahum Melamed(3)
(1)Innofacer, Turfschip 328, 1186XZ Amstelveen, the Netherlands, Willy.Siegel@Innofacer.nl
(2)Qolor, Hoofdstraat 140, 2181EH Hillegom, the Netherlands,
QolorHDJ@gmail.com
(3)The Aerospace Corporation, 2310 E El Segundo Blvd, El Segundo, CA 90245, USA, Nahum.Melamed@aero.org

Keywords: Apophis tracking, Meade telescope, ISS tracking, citizen science, public education

ABSTRACT

The Apophis asteroid 99942 will make a close approach with Earth on 13 April 2029 (1) and can be followed from central Europe and Africa (2). Its trajectory influenced by Earth’s gravity is well predicted. However, there are uncertainties concerning its rotational behavior and the long-term influence on its path (3–6). Changes to its rotation period of at least 27 hours, are predicted, but their magnitude is unclear due to uncertainty of non-homogeneous mass distribution. Gravity interaction with Earth during the flyby may change these rotations and the strength of the semimajor axis drift rate due to Yarkovsky acceleration (4,7). It is therefore of interest to measure Apophis’ rotation combined with its trajectory during the flyby.

The MEADE LX200GPS telescope is primarily designed for astronomical observing and is used to observe celestial and deep-space objects where, after lock-on, tracking is mainly achieved by adjustment of Earth rotation (8,9). Additional adjustments must be made to track an artificial satellite or the Apophis asteroid during the close approach to Earth (10). The tracking data are initially based on open loop calculations. During actual observation, real-time corrections are made through optical tracking with a camera. In addition, the camera will be used to measure rotational changes through Fourier analysis on the apparent brightness (11,12).

A first experiment is planned in 2024-2025 to track the International Space Station (ISS) using the adapted telescope and estimate the tracking measurement precision. The adaptation includes the integration of a camera and software development to calculate the offset from the nominal path. Through the creation of inserted offset-errors from the nominal known path, precision of the optical calculated offset will be derived. In addition, an on-line site will be developed to share information for public education and will present real-time calculations of tracking ISS and Apophis in 2029. The adaptations and the results of the experiment will be presented, as well as suggestions for further upgrade of the system in order to retrieve significant data from the actual Apophis flyby.

References:
1. Giorgini JD, Benner LAM, Ostro SJ, Nolan MC, Busch MW. Predicting the Earth encounters of (99942) Apophis. Icarus. 2008 Jan;193(1):1–19.
2. ESA. ESA - Planetary Defence. 2024 [cited 2024 Jun 11]. Apophis. Available from: https://www.esa.int/Space_Safety/Planetary_Defence/Apophis
3. Pravec P, Scheirich P, Ďurech J, Pollock J, Kušnirák P, Hornoch K, et al. The tumbling spin state of (99942) Apophis. Icarus. 2014 May 1;233:48–60.
4. Benson CJ, Scheeres DJ, Brozović M, Chesley SR, Pravec P, Scheirich P. Spin state evolution of (99942) Apophis during its 2029 Earth encounter. Icarus. 2023 Jan 15;390.
5. Souchay J, Souami D, Lhotka C, Puente V, Folgueira M. Rotational changes of the asteroid 99942 Apophis during the 2029 close encounter with Earth. Astron Astrophys. 2014 Mar;563.
6. Souchay J, Lhotka C, Heron G, Hervé Y, Puente V, Folgueira Lopez M. Changes of spin axis and rate of the asteroid (99942) Apophis during the 2029 close encounter with Earth: A constrained model. Astron Astrophys. 2018 Sep 1;617.
7. Vokrouhlický D, Farnocchia D, Čapek D, Chesley SR, Pravec P, Scheirich P, et al. The Yarkovsky effect for 99942 Apophis. Icarus. 2015 May 5;252:277–83.
8. Kruzhilov I. Small-angle rotation method for star tracker orientation. J Appl Remote Sens. 2013 Nov 19;7(1):073479.
9. Wahr JM. The Earth’s rotation. Annual review of earth and planetary sciences Vol 16. 1988 May 1;16(Volume 16, 1988):231–49.
10. Anderson LG. Satellite tracking with telescope and software [Internet]. [Monterey, California]: Naval Postgraduate school; 2019 [cited 2024 Jun 11]. Available from: https://apps.dtic.mil/sti/pdfs/AD1086919.pdf
11. Riel T, Sinn A, Schwaer C, Ploner M, Schitter G. Iterative trajectory learning for highly accurate optical satellite tracking systems. Acta Astronaut. 2019 Nov 1;164:121–9.
12. Serra M, Curetti M, Bravo SG, Mathe L. Implementation of control algorithm for optical tracking system in Meade LX200-ACF telescope. In: 2017 17th Workshop on Information Processing and Control, RPIC 2017. Institute of Electrical and Electronics Engineers Inc.; 2017. p. 1–6.

Coordinated use of modeling and in-situ radar data can advance our understanding of the internal structure of rubble pile asteroids, essential for planetary defense and planetary science. On April 13, 2029, asteroid 99942 Apophis will pass within 32,000 km of Earth, closer than geostationary orbit. A potential Caltech-led mission could escort Apophis through this encounter, observe its response to Earth’s gravity, and use bistatic radar to map its interior. The mission aims to reveal Apophis' shape, density, internal block and void distribution, and spin state changes. It would perform bistatic radar, mapping the asteroid’s internal structure at tens-of-meter scales and producing 3D backscatter and dielectric constant maps. These observations would offer groundbreaking insights into rubble-pile interiors, though methods for interpreting such data remain an open challenge.

To effectively simulate potential radar observations, realistic asteroid models are necessary. Previous work using the Discrete Element Method (DEM) has modeled Apophis as a lattice arrangement of uniform-sized spheres or a collection of large aggregates of spheres. We have developed an improved DEM model of Apophis using level sets to represent realistic block shapes and with size-frequency distributions of blocks ranging from meters to tens of meters in diameter, similar to those observed on the surfaces of analogous asteroids (e.g. Itokawa) by previous missions. Simulated scenarios explore several internal configurations, such as uniform block spatial distributions, larger blocks near the core or surface, and contact binaries. These models are currently being used to predict Apophis' response to its Earth flyby and can also be used to generate simulated bistatic radar images to help define radar specifications and data volume requirements needed to determine whether the interior is homogeneous or heterogeneous at large scales and constrain the size-frequency distribution and spatial arrangement of interior boulders in greater detail.

This work underscores the synergy between modeling and radar tomography. We discuss how modeling can help define mission requirements and refine data interpretation methods, ensuring high scientific return from radar missions to Apophis or similar asteroids. In turn, radar tomography data can validate and improve models, advancing planetary defense strategies, including asteroid risk assessment and deflection planning.

6ROADS, an independent company, owns a global network of fourteen remote telescopes strategically located across six continents. The primary mission focuses on tracking and surveying man-made objects in Low Earth Orbit (LEO), Medium Earth Orbit (MEO), and Geostationary Orbit (GEO), as well as confirming newly discovered Near-Earth Objects (NEOs) approaching Earth’s vicinity. The backbone of 6ROADS’s observational network consists of high-speed telescopes equipped with state-of-the-art sCMOS sensors, enabling accurate and efficient data collection.

In addition to its operational capabilities, 6ROADS spearheads scientific research into alternative technologies for data acquisition, such as Event-Based Sensors (EBS). EBS technology employs an innovative approach to data collection by recording changes in light intensity as discrete ON and OFF pixel states. This methodology minimizes data generation, optimizing storage and energy usage, and facilitates effective operations in low-bandwidth environments. Furthermore, EBS’s high dynamic range allows for successful observations in challenging environments with extreme contrasts, such as objects near the Sun, where traditional sensors typically fail.

Although EBS technology is still in its early stages, recent advancements indicate its significant potential for deployment in space and remote observational locations. This paper explores the integration of EBS into modern optical telescopes and its transformative implications for NEO observation and planetary defense. By leveraging cutting-edge sensors and a distributed telescope network, 6ROADS demonstrates a forward-looking approach to enhancing planetary defense strategies.

With its extremely large field of view of ≃47 square degrees, which scans the entire northern sky every two nights, the Zwicky Transient Facility (ZTF) is a powerful tool for serendipitous detections of near-Earth asteroids (NEAs). This effort aims to both discover new NEAs and refine the orbital information of known objects, anticipating and mitigating future dangerous collisions. We present a novel pipeline for ZTF images that uses a convolutional neural network (CNN) to improve the detection capability of NEAs. Our work aims to minimize the dependency on human intervention of the current approach adopted by the ZTF. The target NEAs have high proper motions of up to tens of degrees per day and thus appear as streaks of light in the images. We trained our CNNs to find these streaks by using three datasets: a set with real asteroid streaks, a set with synthetic streaks and a set with a mix of real and synthetic, and tested the resultant models on a set of 115 real asteroids. The results achieved were almost identical across the three models: 0.843±0.005 for the completeness and 0.820±0.025 for the precision. No significant differences were found when assessing the quality of the detections; all models performed equally well when characterizing the streaks found in terms of position, angle with respect to the x-axis and length. The average error reported by the three pipelines was 1.84±0.03 pixels for the streak position, (0.817±0.026)° for the streak angle and -0.048±0.003 for the relative error in streak length. In addition, we compared the performance of our pipeline trained with a mix of synthetic and real streaks to that of the human scanners who vet ZTF candidate streak detections by analyzing a larger set of images containing 317 streaks flagged as valid by the scanners. Our pipeline achieved a precision of 99 %, detected 80 % of the streaks found by the scanners and 697 additional streaks that were verified to be real objects. In this case, the pipeline trained with a mix of real and synthetic streaks outperformed the pipeline trained only with real streaks by 10 % in completeness. This disparity in performance was explored to suggest possible reasons. Our results indicate that the new automated pipeline can complement the work of the human scanners at no cost for the precision and find more objects than the current approach. They also prove that the synthetic streaks simulated were realistic and can be used to enlarge training sets with insufficient real streaks or explore the simulation of streaks with unusual characteristics that have not yet been detected. Our pipeline not only shows a strong potential to make new findings in the ZTF data but also can be scaled up to other wide-field telescopes, setting the stage for fast and automated NEA discoveries in the next generation of astronomical surveys.

In 2019, the Catalina Sky Survey invited SPACEWATCH® to collaborate with them and the University of Minnesota on a new survey for near-Earth objects (NEOs) using Steward Observatory’s Bok 2.3-m telescope on Kitt Peak in Arizona to discover faint near-Earth asteroids and to search for Earth Trojans. We propose for 6 to 9 nights of dark/grey time each lunation for the new Bok NEO Survey which had its first observations on November 19, 2019 UT. This is the largest aperture ground-based NASA-funded optical survey for NEOs. With the 90Prime prime focus wide-field imager on the 2.3-m, we can observe and discover objects as faint as V~23.4. Our specific goals are to discover and characterize the population of potentially hazardous NEOs larger than 140m and the presumptive population of Earth Trojan asteroids.

Working together since 2019, as of December 15, 2024, we have submitted over 4600 lines of astrometry of NEOs, comets, and outer solar system objects, including 739 with discovery credit. The NASA Planetary Data System (PDS)’s Small Bodies Node has ranked the Bok NEO Survey as making the fourth-most discoveries published in Minor Planet Electronic Circulars (MPECs) in the past twelve months and over the past five years. Even though the Bok survey began in November 2019, it has already made the eighth-most discoveries since September 1993. Our most recent Bok NEO Survey observing run, spanning November 26 through December 4, 2024 UT, was the most productive yet, discovering 79 new objects, including the impactor 2024 XA1.

SPACEWATCH® was founded by Professor Tom Gehrels and Dr. Robert S. McMillan in 1980 to explore populations of small solar system objects. We began discovering asteroids in the 1980s. We use the Steward Observatory 0.9-m telescope (MPC code 691) on Kitt Peak, Arizona, the Lunar and Planetary Laboratory (LPL) 1.8-m telescope (MPC code 291), and bright time the Spacewatch Cassegrain Camera on the Bok 2.3-m telescope (MPC program codes ^695 and D695) for follow-up NEO observations. We are working on streamlining our precovery search program that identifies images in our archived data that may contain new objects. We also collect time series of observations of NEOs to determine their rotational lightcurve periods and amplitudes.

As demonstrated by the Chelyabinsk event on February 15, 2013, collisions of small (decameter-class) Near-Earth objects (NEOs) with the Earth pose a danger to inhabitants of our planet. These bodies are faint and can only be systematically detected in near-Earth space. Moreover, half of these bodies approach the Earth from the day-time sky and can only be detected by special space-borne facilities
A civil space safety program called "Milky Way" is being developed in Russia. One aspect of this program is addressing the asteroid problem. It has two segments regarding the problem under discussion:
- a ground-based network of wide-field optical telescopes with a 1-meter aperture to search for asteroids on night-time hemisphere.
- a space-based facility consisting of a spacecraft located at the SEL1 point between Earth and the Sun to search for day-time asteroids that are not observable by ground or near the Earth space telescopes.
The payload to detect sunward asteroids is developed by INASAN and is based on the results of the conceptual phase of the SODA project (System of Observation of Day-time Asteroids), which was completed in 2023.
The scientific payload consists of a wide field of view telescope with a 30 cm aperture operates in visible light. Asteroid detection will be carried out using a barrier technique and dangerous objects will be tracked until they approach the Earth. For asteroids on collision orbits, the SODA system provides a 10-hour warning (on average) before impact as well as prediction of the entry point of the asteroid into Earth's atmosphere with an accuracy of 10…200 km. Due to the high completeness of detection of day-time asteroids flying from the Sun, in coming decades SODA will provide almost sufficient information on sunward asteroids posing a real threat.
The scientific goals of the mission are to experimentally validate existing models of small bodies in the Solar System and to search for correlation between close flybys of asteroids near the Earth and meteor shower events.
In 2024 the ''Milky Way L1'' system SRR (System Requirements Review) phase began, the completion date for this phase is middle 2025. Construction of the spacecraft was scheduled to begin in 2026. The spacecraft will carry the second payload for observing the Sun in various wavelengths from X-rays to IR, to measure the magnetic field and detect particles. The responsible institute for the second payload is IKI RAS.
The efficiency of asteroid tracking from L1, and therefore the impact region on Earth, could be significantly improved by using triangulation tracking mode if two spacecraft operated simultaneously. Cooperation within China and BRICS countries is welcome to build a second spacecraft to operate in L1.
A combination of space-based (SODA) and ground-based networks is a viable approach to providing a realistic, real-time warning system for decameter-sized impactors.

Measuring Asteroid Distances from a Single Observatory in One Night with Upcoming All-Sky Telescopes

Keywords: NEO, Detection, New Programs,

Near-Earth Objects (NEOs) pose a significant threat to Earth. The Chelyabinsk meteor impact in 2013 served as a stark reminder of this danger, releasing energy equivalent to 30 times the Hiroshima atomic bomb, causing widespread infrastructure damage and injuring approximately 1600 individuals. Apophis, is an asteroid approximately 370 meters in diameter (roughly the size of three and a half football fields), This asteroid is expected to make a particularly close approach to Earth on April 13, 2029, highlighting the critical need for enhanced NEO observation.

Current detection efforts have cataloged only a fraction of the estimated NEO population, with a tracking rate of less than 0.1%. This low rate is primarily attributed to factors such as time-consuming detection pipelines and software limitations in identifying faint, rapidly moving objects. This paper will explore the importance of
expanding our NEO observation capabilities by:

1. Incorporating the contributions of Next-Generation Space Science (young professionals) through initiatives such as the
   "Developing CNN-Based Detection of Near-Earth Objects" effort.

2. Leveraging the efforts of non-governmental institutions and independent NEO detection campaigns. These campaigns utilize various technologies, including Astrometrica, a powerful tool for astrometric data reduction of CCD images.

Key features of Astrometrica include: Image Processing: Facilitates automatic reference star identification, moving object detection and identification, and a "Track and Stack" function for following fast or faint objects. Data Integration and Sharing: Enables data sharing with the Minor Planet Center (MPC) and facilitates the downloading of MPCOrb data.

Furthermore, this paper will introduce our recently formed NEO Detection Program “look Up is an Asteroid”. This program aims to: a) Contribute significantly to the discovery of NEOs using Astrometrica, b) To provide comprehensive trainings to other professionals from various sectors within the space industry in order to foster their involvement in the field, and c) Unite currently fragmented international independent or non-governmental NEO Discovery efforts into a cohesive network.

This unified approach will foster the growth and development of new independent NEO discovery programs worldwide. This paper will demonstrate that these independent efforts are not merely educational exercises, but genuine scientific endeavors that: Contribute significantly to our understanding of NEOs (NEO Catalog) and inspire the next generation of researchers in planetary defense. By integrating the valuable insights and data generated by these independent efforts, the global community can significantly enhance NEO discovery capabilities and strengthen our collective efforts to protect Earth from potential impacts.

The Taurid Complex is a large interplanetary system that contains comet 2P/Encke, several meteoroid streams, and possibly a number of near-Earth asteroids [1]. The size and nature of the system have led to the speculation that it was formed through a large-scale cometary breakup [2]. Numerical investigations and meteor observations have suggested that planetary dynamics can create a resonant region with a large number of objects concentrated in a small segment of the orbit, known as the Taurid swarm, which approaches the Earth in certain years and provides favorable conditions to study the Taurid Complex [3,4,5].
Here we report a dedicated telescopic search for potentially hazardous asteroids and other macroscopic objects in the Taurid swarm using the 1.2-m Palomar Schmidt telescope as part of the Zwicky Transient Facility survey [6]. Observations were made on October 29 and 31, 2022, when the Earth passed close to the center of the Taurid swarm. We imaged an on-sky area of 1550 square degrees covering 99% of 100-m-class swarm objects. Two sets of moving object detection software were used to search for swarm objects, one specialized in detecting fast-moving, trailed objects and the other focused on point-source objects [7,8], with no swarm objects found. We determine from our non-detection that there are no more than 9-14 H<24 (equivalent to a diameter of D≳100 m) objects in the swarm, suggesting that the Encke-Taurid progenitor was ~10 km in size. A progenitor of such a size is compatible with the prediction of state-of-the-art Solar System dynamical models, which expect ~0.1 D>10 km objects on Encke-like orbits at any given time. We will also discuss the implications of our results for the existence of smaller, Tunguska-sized objects in the swarm, also discussed by Boslough et al. at this conference [9].

This work is supported by NASA program 80NSSC22K0772. DV and DLC are in part supported by NASA Meteoroid Environment Office under cooperative agreement 80NSSC24M0060. Based on observations obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Grant No. AST-2034437 and a collaboration including Caltech, IPAC, the Weizmann Institute of Science, the Oskar Klein Center at Stockholm University, the University of Maryland, Deutsches Elektronen-Synchrotron and Humboldt University, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, Trinity College Dublin, Lawrence Livermore National Laboratories, IN2P3, University of Warwick, Ruhr University Bochum, Cornell University, and Northwestern University. Operations are conducted by COO, IPAC, and UW.

Reference:
[1] Porubcan V & Stohl J, 1987. The meteor complex of P/Encke. Publications of the Astronomical Institute of the Czechoslovak Academy of Sciences, 2, 167.
[2] Clube SVM & Napier WM, 1984. The microstructure of terrestrial catastrophism. Monthly Notices of the Royal Astronomical Society, 211, 953.
[3] Asher DJ & Clube SVM, 1993. An Extraterrestrial Influence during the Current Glacial-Interglacial. Quarterly Journal of the Royal Astronomical Society, 34, 481.
[4] Clark DL et al. 2019. The 2019 Taurid resonant swarm: prospects for ground detection of small NEOs. Monthly Notices of the Royal Astronomical Society, 487, L35.
[5] Spurný P et al. 2017. Discovery of a new branch of the Taurid meteoroid stream as a real source of potentially hazardous bodies. Astronomy & Astrophysics, 605, p.A68.
[6] Graham MJ et al. 2019. The Zwicky Transient Facility: Science Objectives. PASP, 131, 078001.
[7] Ye Q et al. 2019. Toward Efficient Detection of Small Near-Earth Asteroids Using the Zwicky Transient Facility (ZTF). Publications of the Astronomical Society of the Pacific, 131, 078002.
[8] Masci FJ et al. 2019. The Zwicky Transient Facility: Data Processing, Products, and Archive. Publications of the Astronomical Society of the Pacific, 131, 018003.
[9] Boslough M et al. 2025. 2032 And 2036 Risk Enhancement From NEOs In The Taurid Stream. Planetary Defense Conference 2025, submitted.

ASSESSING THE VULNERABILITIES OF THE MEERKAT ASTEROID GUARD

C. Drury (a), M. Frühauf (b) , J.L. Cano (c) , F. Gianotto (a), M. Fenucci (a), L. Faggioli (a)

(a) ESA ESRIN / PDO / NEO Coordination Centre, Via Galileo Galilei, 1, 00044 Frascati (RM), Italy
(b) Technical University of Munich, Lunar and Planetary Exploration, Lise-Meitner-Str. 9, Ottobrunn, 85521, Germany
(c) ESA ESOC / Planetary Defence Office, Robert-Bosch-Straße 5, 64293, Darmstadt, Germany

New asteroids and comets are continuously being discovered in the night sky. Such objects need prompt follow-up before they are lost, so that an early and reliable computation of the impact probability can be completed. Here we present the Meerkat Asteroid Guard [1], an automated imminent impact warning service developed and operated at the ESA NEO Coordination Centre.

Meerkat continually downloads tracklets for unconfirmed near-Earth objects from the NEO Confirmation Page. For many of these new objects, the observation arc length is short. While the object’s plane of sky position and motion may be known with sufficient accuracy, the remaining two parameters required to describe the orbit, the topocentric range and range rate, are not. Such short arcs lead to severe errors and degeneracies in traditional orbit determination methods. To overcome this, we employ the method of systematic ranging [2] [3], whereby a grid of topocentric range and range rates have their orbits fitted with associated error. From this error we derive a posterior probability distribution. By scanning a suitably dense grid, we can produce a statistical description of the most likely orbital solutions, and derive important information such as estimated size and impact probability. Meerkat operates 24/7, delivering warnings of imminent impactors and close approaches via email to subscribed users.

Over its three-year operational lifetime, Meerkat has successfully issued alerts for the past seven imminent impactors, from 2022 EB5 to most recently 2024 XA1. These alerts were vital for coordinating follow-up observations and preparing local authorities for fireball events.

The importance of an imminent impactor warning system cannot be overstated. With the advent of new surveys from ESA Flyeye, the Vera Rubin Observatory and NEO Surveyor, the number of new detections is predicted to increase dramatically. To ensure our readiness, this work evaluates the performance of Meerkat against a large dataset of real and simulated observations. We explore how our systematic ranging algorithm can be configured to optimise solution speed and accuracy. False positive alerts and anomalous results are investigated to find potential causes. This work is necessary to ensure our systems have been rigorously tested and are fully prepared for the large data influx anticipated in the coming decade.

References:
[1] F. Gianotto, J. Cano, L. Conversi, L. Faggioli, M. Fenucci, D. Föhring, M. Frühauf, D. Koschny, R. Kresken, M. Micheli, et al., Meerkat Asteroid Guard - ESA’s Imminent Impactor Warning Service, in: 2nd NEO and Debris Detection Conference, p. 49.
[2] S. Chesley, Very short arc orbit determination: the case of asteroid 2004 FU162, Proceedings of the International Astronomical Union 2004 (2004) 255–258.
[3] D. Farnocchia, S. Chesley, M. Micheli, Systematic ranging and late warning asteroid impacts, Icarus 258 (2015) 18–27.

In this work, we present the first results of the ATLAS (Asteroid Terrestrial-impact Last Alert System) unit that will be installed by the Instituto de Astrofísica de Canarias (IAC) at Teide Observatory (TO) on Tenerife Island, Spain, in January 2025. The ATLAS-Teide unit will operate as part of the ATLAS network (https://atlas.fallingstar.com/) under an agreement between the IAC and the ATLAS team at the University of Hawaii, encompassing both operational and scientific exploitation.
ATLAS, developed by the University of Hawaii and funded by NASA, is an asteroid impact early warning system consisting of four telescopes (two in Hawaii, one in Chile, and one in South Africa). Each ATLAS unit surveys a quarter of the night sky, making four observations of each field at hourly intervals, and is capable of detecting asteroids with a brightness of V=19.5 mag. This system aims to identify small (~20 m) asteroids on impact trajectories several days in advance and larger (~100 m) asteroids weeks prior to impact. The current ATLAS configuration uses 50 cm Wright-Schmidt telescopes paired with CCD cameras that image a 30 deg^2 field of view in a single exposure.
ATLAS-Teide introduces a novel and more cost-effective modular design, employing commercial off-the-shelf (COTS) components. Each module consists of four Celestron RASA 11 telescopes mounted on an equatorial Direct Drive mount PlaneWave L550, with QHY600PRO CMOS cameras capturing a shared field of view. Each module achieves an effective aperture equivalent to a 56 cm telescope, with a 7.5 deg^2 field of view and a plate scale of 1.25"/pixel. A prototype module, ATLAS-P, was installed in November 2022 at an existing clamshell facility at TO to test the system's capabilities and develop the necessary control and image processing software.
ATLAS-P saw its first light on November 14, 2022, and during its commissioning phase demonstrated compliance with all mechanical, electrical, and optical requirements. Frames combining 5×6-second exposures simultaneously captured by the four telescopes consistently detected asteroids as faint as V=20. ATLAS-P also enabled the development of software for fully robotic operation and simultaneous control of the four cameras.
The full ATLAS-Teide installation will consist of four such modules housed in a roll-off roof building. This configuration will cover the same sky area as the existing ATLAS units but offers significant advantages in cost, maintenance, and flexibility. For instance, all modules can point to the same field to achieve an effective aperture equivalent to a 1.1 m telescope, allowing the detection of fainter near-Earth objects (NEOs). Alternatively, shorter exposure times and advanced detection techniques, such as synthetic tracking, can improve the detection of very fast-moving NEOs. This innovative approach positions ATLAS-Teide as a transformative addition to the global asteroid impact monitoring network.

The European Space Agency’s (ESA) Flyeye telescopes will play a crucial role in global planetary
defense efforts, with their unique optical design inspired by the compound eyes of a fly. These telescopes
feature an expanded field of view, allowing a more efficient survey of the sky and improving the
detection of potentially hazardous Near-Earth Objects (NEOs).
We present the status of the Flyeye-1 telescope, currently located in Matera, Italy. Highlights include
milestones in manufacturing, hardware integration, and plans for its relocation to the Mt. Mufara
observatory. The presentation covers the telescope’s design features, survey strategy, data processing
architecture, challenges encountered, and preliminary results from the testing phases.
We also introduce Flyeye-2, presenting its enhanced specifications and design progress, along with
its prospective locations in the Southern Hemisphere. Looking forward, we present plans for the network’s
full deployment and its anticipated role in advancing global planetary defense efforts in the LSST
era.

We are part of an expertise group of over two dozen astronomers, computer scientists, data scientists and digital Big Data research platform experts at 11 universities and research institutes in South Africa and Europe. We study Near-Earth Objects (NEOs) for Planetary Defence and scientific purposes.

NEO Discovery. In this talk, we present our programme and results for algorithms and digital data analysis platforms for machine learning-assisted Near-Earth Object discovery, monitoring, and polarimetric characterisation in astronomical surveys for Planetary Defence and scientific purposes.

We present the performance of detecting streak-like features in large astronomical surveys using classical and machine learning methods, focusing on Near-Earth Objects. Our current focus is ESA’s Euclid Survey, Rubin’s Legacy Survey of Space and Time, and surveys with INAF’s VLT Survey Telescope. We present results using Convolutional Neural Networks (CNNs) in comparison to classical methods (e.g., SourceXtractor, StreakDet). We present our preliminary assessment comparing Vision Transformers and CNNs.

NEO Characterization. The VLT Survey Telescope's polarimetric survey mode will be commissioned in 2026. We present our first analysis of polarimetry's value for NEO Planetary Defence and science and the potential of machine learning applications in NEO polarimetry.

NEO Digital Platforms. We present the challenges experienced in our digital Big Data research platforms to perform machine learning-assisted Near-Earth Object discovery and monitoring in astronomical surveys. We have a leading role in digital Big Data platforms for ESA (Euclid Mission) and for ESO instrumentation (VST-OmegaCAM, VLT-MUSE, ELT-MICADO/METIS). These platforms build on our AstroWISE Information System, which was developed for astronomical research. Our NEO discovery, astrometric, and photometric monitoring use these platforms and their massive data archives, compute clusters, and databasing.
In this talk, we describe the lessons learned from taking this piggybacking approach. The synergies between NEO investigations and astronomical science lie in (i) common instrument and software requirements on astrometric and photometric precision calibration and (ii) common requirements on databasing and IT to handle such large datasets. The challenges lie in bridging the gap between communities and the sometimes non-natural fit with the traditional tasks of universities and science funding agencies. We conclude the presentation by giving an outlook on how to strengthen the synergies and overcome the challenges. This includes future plans to link the astronomical databases to the open-source Tudat orbit estimation software for automated ephemeris updates of target NEOs, and dynamical validation of new observations.

List of relevant publications involving our team: Astrophysics Data System NEO Planetary Defense library

Abstract: Since 1960 TLS (IAU code 033)
has operated the largest imaging Schmidt telescope
with a correction plate of 1.34 m in diameter. Initial
asteroid work by Freimut Börngen aimed at discover-
ing main-belt asteroids. In 2010, it was resumed by
joining the worldwide NEOCP effort. TLS became a
sensor in ESA’s NEOCC program in 2019. It is now
one of the major European observatories with regard
to NEO follow-up. Recently, the first NEA discoveries
succeeded.

Asteroids are key to unlocking the secrets of our solar system's formation and evolution, as well as assessing potential threats to Earth from impacts. This paper presents a thorough account of a significant asteroid search campaign conducted as part of an international collaborative initiative focused on identifying and tracking near-Earth objects (NEOs) and main belt asteroids (MBAs).Employing the advanced Astrometrica software, the high-resolution astronomical images obtained from both professional and amateur observatories were analysed. This campaign not only identified and cataloged new asteroids, significantly enriching the global asteroid database, but also confirmed the existence of known objects. Our comprehensive analyses enabled us to measure asteroid positions precisely using right ascension and declination and to calculate crucial orbital parameters necessary for determining accurate trajectories. Furthermore, tracking NEOs provided vital information for assessing potential impact risks.This study firmly establishes the indispensable contributions of citizen science in enhancing asteroid discovery and tracking initiatives. The results reinforce the urgent need for continuous asteroid search campaigns to deepen our understanding of small solar system bodies and to fortify planetary defense systems. We strongly advocate for the integration of cutting-edge machine learning algorithms and the fostering of international cooperation to maximize and elevate asteroid search efforts, ensuring a safer future for our planet.

Keywords: near-Earth object, planetary defense, survey, infrared, detect

The Near-Earth Object (NEO) Surveyor mission is a key element in our future planetary defense portfolio, which will provide a complete survey of our solar system in the infrared.

The mission is designed to detect, track, and characterize small bodies throughout our solar system.
By congressional mandate, NASA must discover more than 90% of all asteroids and comets that are larger than 140 meters in diameter and could potentially impact Earth. NEO Surveyor will provide critical decision support for stakeholders who must assess the risks of NEO impacts to Earth and identify potential mitigation strategies.
By using two heat-sensitive infrared imaging channels, NEO Surveyor will be able to detect NEOs that ground-based telescopes or space-based visible instrumentation are unable to detect due to the objects' darkness and the limitations of ground-based surveyal. These objects can "sneak through" our existing detection methods and are large enough to cause major regional damage if one were to impact Earth.

The Space Dynamics Laboratory, under the leadership of the Jet Propulsion Laboratory and in partnership with other organizations, is playing a critical role in subsystem development and observatory-level assembly, integration, and test. This presentation will review challenges, lessons learned, and critical accomplishments in the preparation for launch of NEO Surveyor.

In this study, we propose the method of frame stacking which is implemented in celestial (equatorial) coordinate system. This method allows to prolong the “effective exposure time” of near-Earth objects (NEOs) increasing the efficiency of capturing faint objects. Additionally, it can be realized using CCD frames obtained by several optical systems simultaneously or at different epochs.

Stacking of CCD frames is quite common practice in astronomical imaging. It is usually done by comparing patterns or directly overlying images and requires all frames to be obtained by the same telescopes and in similar circumstances. The proposed use of equatorial coordinates allows to stack frames, which have different scales, distortions, framing, and epochs. This approach requires an astrometric solution for all involved frames, i.e., transformation from pixel coordinates to equatorial coordinate system. Stacked frame is generated in a rectangular coordinate system, having as coordinates right ascension and declination. Thus, implementation of this approach ensures the possibility to combine frames obtained by different optical systems at different locations, as well as to increase the brightness of NEOs also in situations where a number of circumstances, such as weather, astroclimate, hardware capabilities, specific locations, are forcing to put up with short exposures, small sensors and bright sky background.

In this work the methodology of astrometric processing is presented. We provide observation cases highlighting advantages of the method of frame stacking for NEO detection and tracking. The software package used in this study was developed at the Institute of Geodesy and Geoinformatics (GGI). Observation results were obtained by twin 41-cm telescope system of the University of Latvia.

Acknowledgement: The research is financed by the Recovery and Resilience Facility project "Internal and External Consolidation of the University of Latvia", No. 5.2.1.1.i.0/2/24/I/CFLA/007.

The Chelyabinsk meteor entered Earth’s atmosphere on 15 February 2013, producing a shock wave that injured about 1,500 people and damaged thousands of buildings. Despite its relatively large size (~20 m), the progenitor asteroid approached Earth undetected. Its radiant was too close to the Sun for standard near-Earth asteroid (NEA) search programmes. In addition, it was very faint due to the high phase angle illumination geometry, and very fast moving.
We examine the potential for early detection of similar objects using current and upcoming infrared (IR) space initiatives, such as ESA’s planned NEOMIR mission. IR observations from space offer key advantages: (i) enhanced Sun-asteroid contrast (compared to visible wavelengths), (ii) small, fast-rotating object are (nearly) isothermal which make IR detections at high phase angles easier, (iii) immediate good-quality size estimation upon IR detection, and (iv) feasibility of observations near the Sun.
Our study evaluates the possibilities and limitations of detecting a Chelyabinsk-type object on a similar orbit, addressing challenges such as high zodiacal light background and fast apparent motion, requiring synthetic tracking techniques. Key questions include: optimal IR wavelengths for detection, best telescope placement in space, strategies for high-motion targets, and practical considerations when observing near the Sun.
We estimate that a 20-m object could be detected with a 0.5 m telescope in space, at mid-IR wavelengths, with a lead time of 5–10 days. The large uncertainty in the calculation of the detection lead-time is mainly related to uncertainties in the flux predictions for small, possibly fast-rotating asteroids seen under very extreme phase angles. However, technical challenges, including detector operations at high sky background, telescope straylight problems for observations close to the Sun, and fast orbit determination also must be overcome to achieve reliable early warning capabilities

The Vera Rubin Observatory Legacy Survey of Space and Time (LSST) will provide an unprecedented number of potential Near-Earth Object (NEO) discoveries. Many of these new NEO detections will require additional detections for confirmation and orbit refinement. While follow-up strategies have been actively developed, it is expected to take a significant dedicated amount of time and resources to follow up on all potential LSST detections. An alternative approach to provide additional detections of potential new NEOs is to search for these objects in archival image data from past and current surveys; such methods are often referred to as pre-discovery. The challenges with NEO pre-discovery include the large search space needed due to high trajectory uncertainty and the limited sensitivity of sensor systems from past surveys in comparison to LSST. To address these challenges, we have developed a new efficient synthetic tracking pipeline to search for and detect NEOs beyond the single-frame limit over a large search space. The pipeline utilizes divide-and-conquer techniques to rapidly search a large trajectory hypothesis space and combine the signal across frames over time to aggregate sufficient signal-to-noise ratio for detection. This technique has been previously demonstrated to provide significant speedup in comparison to traditional search approach to provide detections of solar system objects up to 3 visual magnitudes fainter than the single-frame detection limit with limited a priori state knowledge. We present results from our proof-of-concept demonstration of NEO pre-discoveries with image data from the Transiting Exoplanet Survey Satellite (TESS) mission, showing that it is possible to find NEOs fainter than the instrument’s single-frame sensitivity limit and without precise ephemeris knowledge. This pipeline can be adapted to perform NEO pre-discovery as well as follow-up search with data from several existing surveys to complement follow-up efforts to rapidly confirm new NEOs in the age of LSST.

Konkoly Observatory is conducting the most successful NEO survey project in Europe with a total number of NEOs found in the past four years in excess of 250, with three imminent impactors discovered between 2022 and 2024. Recently, supported by the European Space Agency, we started the implementation of a new search technique that is using machine learning algorithms to accelerate real-time image analysis with the scope of finding extreme trailed images of the smallest and nearest NEOs passing by. We have created a custom deep-learning model that was trained on a large dataset of astronomical images and their associated annotations. In addition to the real observations from the Piszkesteto Mountain Station of the Konkoly Observatory, we have also created a huge synthetic photorealistic training dataset to improve the precision and accuracy of the neural network. As a result, the model successfully learnt to recognise patterns and features in the images that are indicative of NEOs and space debris. The main goal was to have an optimized deep learning model to perform this analysis in real-time, providing quick and reliable detection that is made possible by the AI-based robust image-artifact decomposition for false positive suppression. The outcome of this project is a service that can quickly and accurately detect NEOs and space debris on astronomical images, potentially increasing the number of discoveries and improving the speed and reliability of the discovery process. The system has been evaluated using a set of rigorous tests and is benchmarked against existing methods. We provide valuable insights into the feasibility of using deep learning techniques for this type of image analysis problem and will lay the groundwork for future work in this field.

The first NEO observations were conducted in 2017 using the new wide-field telescope of the “Sazhen-S” quantum-optical station of the National space Facilities Control and Test Center (NSFCTC) of the State Space Agency of Ukraine. Regular observations, including the follow-up of new objects discoveries, began in 2019. By the end of 2024, three telescopes of NSFCTC in different parts of Ukraine have already been participating in such observations.

Despite the fact that NEO observations are not the main task of these optical sensors, more than 15,000 observations of various NEOs were obtained in the period of time from 2017 to 2024, and participation was taken in follow-up of the discovery of more than 250 new NEOs, including more than 10 PHAs.

The software tools for automatic planning of observations and analysis of the obtained results as well as the software for processing NEO observations were developed.

In the future, it is planned to increase the limited magnitude of the telescope to expand the capabilities to follow-up the discovery of new NEOs.

The South African Astronomical Observatory (SAAO) has made significant contributions to the observation and characterisation of near-Earth asteroids (NEAs), supporting global planetary defense efforts. Located near the town of Sutherland in the Northern Cape, SAAO's diverse array of telescopes, ranging from 10-m to 1-m in diameter, offers capabilities in spectroscopy, multi-filter photometry, and polarimetry, with rapid-response options enabled by the robotic 1.0-meter Lesedi telescope. Many of these facilities have contributed data to the international NEA planetary defense exercises organised by the International Asteroid Warning Network (IAWN), including participation in the "2012 TC" (Reddy et al. 2019), "Apophis" (Reddy et al. 2022), and, most recently, the "2023 DZ2" (Reddy et al. 2024) campaigns. Several telescopes located at the SAAO also contributed to the ground-based monitoring of the DART spacecraft's impact with Dimorphos (Fitzsimmons et al. in prep.).

With SAAO hosting one of the nodes of the Asteroid Terrestrial-impact Last Alert System (ATLAS, Tonry et al. 2018) and making good progress with its "Intelligent Observatory" or "IO" initiative (Potter et al. 2024), the observatory has significantly enhanced its automated follow-up capabilities. This setup now allows for rapid same-night follow-up observations of newly discovered NEAs identified by ATLAS.

This presentation will highlight the facilities at SAAO used for NEA follow-up and characterisation, both in the past and present. It will also showcase some of the scientific highlights and discuss future plans to utilise new or currently underused facilities available on-site.

The OSIRIS-REx and Hayabusa2 missions yielded a wealth of data that is transforming the understanding of rubble-pile asteroids, providing unprecedented insights into their composition, structure, and evolution. Rubble-pile asteroids are highly porous, loosely bound collections of rocks and boulders held together primarily by gravity, with minimal cohesion, and measuring less than a few kilometers in size [1]. The power-law distribution of asteroid sizes indicates that rubble-pile asteroids are the most common class of near-Earth asteroids, making them of significant interest for planetary defense initiatives [2]. However, there is limited data on gravity field measurements and observations for rubble-pile asteroids, and no measurements for sub-kilometer-sized asteroids exist aside from OSIRIS-REx and Hayabusa2 mission data [1]. Therefore, there is a significant gap in understanding the density distribution and surface and subsurface properties of rubble-pile asteroids, which limits the scope and success of future planetary defense initiatives involving rubble-pile asteroids.

This research focuses on developing a high-fidelity, component-based density model of asteroid Bennu, leveraging gravity field measurements and sample return data from the OSIRIS-REx mission. Initial work using a spherical model highlights significant density heterogeneity, including an under-dense core, an under-dense equatorial bulge, a dense subsurface layer, and a boulder-strewn surface regolith. Figure 1 illustrates these components and presents various core size configurations. The next step involves replacing the spherical model with a 3D shape model of Bennu and calibrating it to match the measured gravity coefficients obtained by OSIRIS-REx. Furthermore, granular mechanics simulations, implemented through the LMGC90 platform—a specialized tool for modeling granular materials and their interactions—will enable detailed investigations of vehicle interactions with Bennu’s surface and subsurface properties [3].

This work advances understanding of Bennu’s internal structure and provides a validated framework for modeling rubble-pile asteroids. These results will inform future planetary defense strategies and mission designs targeting rubble-pile asteroids, including those related to resource extraction and asteroid deflection.

References
[1] D. J. Scheeres, et al., Heterogeneous mass distribution of the rubble-pile asteroid (101955) bennu, Science Advances 6 (2020) eabc3350.
[2] E. B. Bierhaus, et al., A subsurface layer on asteroid (101955) bennu and implications for rubble pile asteroid evolution, Unpublished Manuscript (2023).
[3] P. Sanchez, M. Renouf, E. Azema, R. Mozul, F. Dubois, A contact dynamics code implementation for the simulation of asteroid evolution and regolith in the asteroid environment, Icarus 363 (2021) 114441.

This work presents the results of an observation campaign conducted in the second half of 2024 and which will last until the first half of 2025, aimed at the photometric characterization in the BVRcIc bands of the brightest near-Earth asteroids observable from the northern hemisphere.
The observations were mainly conducted using the “G.D. Cassini” 1.52-m F/4.8 Ritchey-Chrétien telescope of the Loiano Astronomical Station (IAU 598), managed by the Astrophysics and Space Science Observatory of Bologna. The Bologna Faint Object and Spectroscopic Camera (BFOSC) was attached to the telescope, equipped with a Princeton Instruments EEV 1340 × 1300 pixel back-illuminated CCD with a 20 μm pixel size. Broad-band Johnson/Cousins BVRc Ic filters were used to measure the asteroid’s colours. The second instrument used was TANDEM, Telescope Array eNabling DEbris Monitoring (IAU D98). TANDEM consists of a combo of four customized and independently steerable 35 cm f/3 Newtonian telescopes, each equipped with a Moravian C4-16000 camera, observing through the
BVRc Ic filters of the Johnson-Cousins system.
Until now, six near-Earth asteroids have been observed and are expected to reach fifteen at the end of the observation campaign. Each asteroids were characterized by colour index, rotation periods, absolute V magnitude and effective diameter. For the brightest asteroids in the TANDEM range, it is possible to perform multi-colour photometry simultaneously, as was done for 2024 MK.

Ground-based asteroid surveys have excelled at finding new near-Earth objects (NEOs) over the last three decades. However, the characterization of those bodies often lags due to the increased observation time needed to determine physical properties. With the Vera Rubin Observatory coming online later this year, this problem will only become more apparent. We present a newly funded NASA PDCO observational project tasked with physically characterizing hundreds of NEOs over the next four years to help keep up pace with the rate of discovery.

This research will focus on measurements of asteroid lightcurves and aims to be complementary to existing lightcurve efforts (e.g., Warner, Pravec, MRO and MANOS, LCO). The primary goal of our observations is to determine rotation state information for NEOs that are the targets of radar observations. Radar measurements are improved and can be performed more quickly with the inclusion of known spin information, but this information is sometimes not available at the time of radar observations. Optical telescopes can observe incoming NEOs at farther geocentric distances and provide this information to radar observers in advance. The rotation rate of the asteroid must be known for radar observations to accurately estimate the size and volume of the asteroid, which would be critical in the event of an impending impactor. We will also use this project to continue supporting International Asteroid Warning Network (IAWN) observation campaigns, especially for lightcurve observations and collaboration with radar teams.

In addition to supporting radar observations and IAWN campaigns, this work will identify new binary asteroid systems. Among NEOs with diameters greater than 300 m, 15±4% of objects have been found to be binary systems (Pravec et al. 2006). Our observations will focus on NEOs with diameters less than 300 m to determine if the binarity fraction extends to this smaller size range. Understanding this will improve our understanding of binary asteroid formation mechanisms in the solar system.

References:
Pravec, P., 56 colleagues, 2006. Photometric Survey of Binary Near-Earth Asteroids. Icarus 181, 63- 93. DOI: 10.1016/j.icarus.2005.10.014

Thousands of Near Earth Objects (NEOs) are discovered every year, but only a small number of these have their compositions determined. In fall, 2024, we have begun a new program to determine the rough taxonomies and therefore compositions of at least ~1000 very small (absolute magnitude >25, or diameters <30 meters) NEOs over a three year period using the MuSCAT3/4 simultaneous four-channel imagers on the Las Cumbres Observatory (LCO) 2-meter telescopes. We will answer two science questions: (1) To what extent does the measured compositional distribution of small NEOs match the predicted distribution based on the Granvik dynamical model? and (2) How much discrepancy is there between the compositions of the smallest NEOs and the meteorite collection? This project is highly relevant for planetary defense, in that we will determine the distribution of compositions of NEOs. We will characterize some 10% of all NEOs discovered each year with a very modest amount of telescope time (67 hours per year).

NEOs can have rotation periods from seconds to hours, and traditional single-filter NEO observations would require filter cycling (r-g-r-i-r-zs-r or similar: seven exposures) to correct for lightcurve effects before NEO color could be determined. However, because of MuSCAT's powerful technique of making simultaneous multi-filter observations, there will be no lightcurve ambiguity introduced into our measurements; there is no offset in time between measurements at different wavelengths. Furthermore, these observations could also allow the detection of rotational heterogeneity.

This is a very efficient and cost-effective program to characterize a large number of
very small NEOs that will not be characterized by any other program. NEO spectroscopy programs rarely observe targets with V>18 – a limit given by the sensitivity of IRTF/SpeX, which is the most commonly used NEO characterization facility, and which is used by MANOS and MITHNEOS to observe some 60--80 NEOs per year between the two programs – but our LCO targets will be as faint as V=22. The work proposed here is highly complementary to other NEO characterization programs.

This project could not easily be carried out with LSST data. Most moving objects will be observed hundreds of times by LSST over its ten year period, but because the observations are random in rotational phase and filter, it will take many years to provide enough measurements to resolve the lightcurve and measure the color for any given asteroid. Furthermore, many NEOs have long synodic periods and may not be observed often during the primary LSST survey, which means that their colors may never be measured from LSST data. Therefore, this project is highly relevant and even in the era of Vera C. Rubin Observatory and the Legacy Survey of Space & Time.

In this presentation we will show first results from this survey, from the 2024B and 2025A semesters.

This project is supported by the NASA YORPD program.

Rapid reconnaissance and characterization of asteroids and comets is one of the stated priorities for planetary defense in the 2023 decadal survey on planetary science and astrobiology1. Traditional asteroid reconnaissance spacecraft like OSIRIS-REx, Lucy, or Psyche have years long development cycle to launch, extensive post-launch trajectory arrival times, and cost hundreds of millions of dollars. With short warning times of a few years or less, that does not leave much time to develop a spacecraft, fly the mission, and collect necessary characterization data to inform mitigation activities and disaster planning accordingly.

We propose the use of an articulated vane solar sail spacecraft or sailcraft to accomplish an asteroid or comet reconnaissance mission as a flyby or rendezvous that would be faster to respond and cheaper to develop and operate compared to traditional spacecraft missions.

Sailcraft provide propellant free propulsion that can reach high velocity and short arrival times to inclined orbits that chemical or low thrust propulsion spacecraft cannot achieve in some cases. This new type of fractionated solar sail that has been under development for the past decade highlighting improved attitude control and less structural mass than the large sheet sailcraft designs. The flexibility of the mission design space is significant given the low overall sailcraft mass, allowing a constellation to be built and launched into station-kept orbits at several distances from the Sun for optimized rapid deployment toward a newly discovered asteroid. The sailcraft would perform routine scientific tasks at their respective heliocentric stations and configure into a rapid reconnaissance mission at the discovery of a new object.

In this paper we investigate several planetary defense rapid reconnaissance mission scenarios using simulated Earth impact asteroid and comet trajectories2 with short warning times to determine how effective a sailcraft mission architecture is for timely flybys or rendezvous. We also discuss current sailcraft development, cost, and realistic added mission objectives to maximize the science return.

References:
1. National Academies of Sciences, Engineering, and Medicine. 2023. Origins, Worlds, and Life: A Decadal Strategy for Planetary Science and Astrobiology 2023-2032. Washington, DC: The National Academies Press. https://doi.org/10.17226/26522.

1. NASA Jet Propulsion Laboratory, “Hypothetical Impact Scenarios,”
   https://cneos.jpl.nasa.gov/pd/cs/

Rapid reconnaissance flyby missions are the fastest means of obtaining asteroid characterization data in a planetary defense scenario. However, the small masses of potentially hazardous asteroids (PHAs) require unreasonably or impossibly close flyby distances to achieve useful mass measurements with ground-based tracking, the current state of practice. This capability gap limits the value of rapid reconnaissance flyby missions and means that decision makers are missing critical information in a PD scenario (National Science & Technology Council, 2018).

Recent research has identified that relative tracking between multiple spacecraft can significantly increase flyby mass measurement sensitivity (e.g., Christensen 2021, Bull 2021, Walker 2021). In these approaches, the flyby spacecraft deploys one or more trackable test-masses prior to the flyby. These test-masses are intended to pass very close to the asteroid, within 1-3 body radii of the surface. The short range of the test-mass to the asteroid produces a large perturbation to the test-mass’s trajectory. The relatively short distance between the host spacecraft and the test-mass (10’s of km) provides a high accuracy measurement of this perturbation, allowing for a more sensitive mass determination.

This study evaluates a selection of concepts to achieve this relative tracking, including: passive optical tracking, active RF tracking (range and Doppler), and precise laser ranging. We also consider the impact of adding attitude control and maneuvers to the test-masses. These techniques are modeled in the context of two reference scenarios: the 2025 PDC hypothetical asteroid and a very high speed (35 km/s) hypothetical encounter.

This paper expands on former studies by modeling the full encounter concept-of-operations with representative spacecraft models. We model ground tracking throughout cruise and flyby operations, optical navigation (when the asteroid is detectable), pointing constraints, approach targeting maneuvers, and a practical spacecraft and measurement schedule.

Given that the measurement is very sensitive, the simulations were conducted using two independent orbit determination tools: the commercial tool Orbit Determination Tool Kit (ODTK) and the NASA JPL tool MONTE.

Based on this research, we will update and expand Figure 1, which shows the sensitivity of flyby mass determination as a function of asteroid diameter and flyby speed, for each of the measurement techniques. Historically, asteroid flybys have been to much larger targets than we expect in a planetary defense encounter (100’s of meters). Once updated, this figure will provide a reference for quickly determining what techniques are viable for a given flyby encounter. This is intended to be a guide for flyby reconnaissance mission design.

{fig1.png}

Figure 1: Expected mass determination performance based on simulation for all four architectures overlaid with results from historical missions and planned Lucy mission targets. Here, mass is considered obtainable if the post-flyby mass uncertainty is better than 25% 1σ. (This figure is currently in draft form.)

Acknowledgements: This work was supported through a grant from NASA’s Planetary Defense Coordination Office, award number 80NSSC23K0501.

REFERENCES

• Bull, R., R. Mitch, J. Atchison, J. McMahon, A. Rivkin, and E. Mazarico, “Optical Gravimetry mass measurement performance for small body flyby missions,” Planet. Space Sci., vol. 205, p. 105289, Oct. 2021.
• Christensen, L., R. S. Park, and J. F. Bell, “Estimating asteroid mass from optically tracked radio beacons,” J. Spacecr. Rockets, vol. 58, no. 2, pp. 444–455, 2021.
• National Science & Technology Council, 2018. National Near-Earth Object Preparedness Strategy and Action Plan, National Academies.
• Walker, L., M. Di Carlo, C. Greco, M. Vasile, M. Warden, “A mission concept for the low-cost large-scale exploration and characterisation of near earth objects”, Advances in Space Research, vol 1. no 67, 2021.

Telescopic characterisation of asteroids and the study of meteorite geochemistry in the lab are fundamentally linked: they study the same objects. However the two disciplines have been mostly disjointed so far, if we exclude the handful of asteroid sample return missions. If we can detect and characterise an asteroid while it is in space, and recover meteoritic samples of it after it impacts, we can close this loop unambiguously.

Set to begin science observations in 2025, the Vera Rubin observatory with its 10-year Legacy Survey of Space and Time (LSST) is going to revolutionise many fields of astronomy. While increasing the number of known asteroids by nearly an order of magnitude, it will also detect 1-10 small asteroids just before they impact the Earth. The current generation of telescopes has so far detected 11 asteroids before impact, including 4 that have subsequently been observed as fireballs and for which meteorites have been recovered. This is just a taste of what is to come with LSST, starting end-2025.

Closing the astronomy/geology loop with impacting asteroids is not without challenges. With an imminent impactor typically detected only hours before impact, this leaves little time to bring to bear more specialised instruments than those that provide astrometry and photometry. Ideally spectroscopy and radar techniques will be required for adequate in-space characterisation. Spectroscopy has only been achieved once so far (2008 TC3), and spectro-photometry also once (2022 WJ1). For LSST targets, the facilities delivering these observations have to ideally be located in the Southern Hemisphere.

Unlike a typical meteor, a metre-size asteroid impacting our atmosphere creates a fireball that outshines the full moon, visible night or day. Imminent impactors are set to become focus events for the Planetary Defence community to communicate to the wider public, enabling large numbers of people, including residents of light polluted cities, to witness the spectacle.

See attached abstract

The International Asteroid Warning Network (IAWN) is an organized network established in 2013 and sanctioned by the United Nations to coordinate worldwide entities involved in the detection, tracking, and characterization of Near-Earth Objects (NEOs). IAWN provides means of communicating and developing plans and protocols for responding to impact threats by obtaining and processing observational information into actionable definitions of physical parameters. In order to develop response methodologies, and test the readiness of IAWN participants to characterize such threats, IAWN frequently organizes campaigns of chosen targets which include a corps of global volunteer participants comprised of observers, modelers, and decision-makers (cf. Kelley et al. 2025 – this conference). While our past campaigns regarded aspects of measurement, modelling and characterization of Near-Earth asteroids (NEAs) on differing timescales, no such campaign has been carried out for a target that is cometary. Comets present unique challenges for accurate astrometric measurements and orbit predictions. Cometary bodies are extended with morphological features (comae and tails) that can systematically pull their centroid measurements off their central brightness peak, increasing the uncertainty of their fitted orbits. Furthermore, near-Earth comets (NECs) undergo nongravitational acceleration from gas and dust mass-ejection that alters their orbits over time, and many undergo frequent orbital perturbations by close encounters with Jupiter and other giant planets. NECs represent a significant fraction of the known NEOs with sizes ~1 km or larger. Therefore, they represent a critical impact-hazard we must be ready to characterize in a timely manner. We will present the IAWN plans to undertake a comet observation campaign, which will include a workshop on techniques to improve an observer’s cometary astrometric measurements, an observing campaign on a selected comet, a period of analysis of the observing results, and a summary of lessons-learned from the exercise.

Asteroids show significant variation in the polarisation properties of their reflected light, which are diagnostic of their surface mineralogy, geometric albedo, and texture. These properties have historically been used to characterise them; however, this remains an under-explored method for their taxonomic classification. Potentially Hazardous Asteroids (PHAs) form a particularly important sample of observable asteroids due to their potential for collision with the Earth and their near passes, which offer opportunities for close study with telescopes or intercepting spacecraft.

Using the 2-metre Liverpool Telescope (LT) and its polarimeter, MOPTOP, robotic linear polarimetry was performed for five PHAs - Didymos, 2023 BU, 2014 HK129, 2010 XC15, and 2006 BE55 - and one Near-Earth Asteroid, 2015 RN35. For three of these objects, the author is not aware of any prior polarimetric data. At least one linear polarisation measurement was made for all six asteroids; depending on the number of observations, further properties could also be determined. For the three asteroids with greater than one data point, a phase-polarisation relationship was constructed, and the geometric albedos and inversion angles were calculated. Classifying asteroids is significantly easier at high phase angles, since the phase-polarisation curve morphology diverges significantly between classes in this region. Even a single measurement at a high phase angle (> 40º) hence holds significant diagnostic power. A classification was therefore deduced for all six asteroids according to the established Tholen taxonomic system. Inferences were thereafter made about their regolith composition, density, and porosity.

The polarimetric properties of the binary asteroid Didymos-Dimorphos were characterised in detail, motivated by the impact of the DART spacecraft upon Dimorphos mere weeks prior to the commencement of this study's observations. Didymos appeared to return to its pre-DART impact polarimetric behaviour within four weeks: no detectable polarimetric signature was observed from the impact’s debris tail, suggesting the tail had dissipated to the point of being undetectable by MOPTOP. In addition to the geometric albedo and inversion angle, the magnitude and phase angle of Didymos’ polarisation minimum were estimated - perhaps for the first time. Remarkably, our results are very similar to those obtained with the VLT: a telescope four times the size of the LT with approximately sixteen times its collecting power.

The Liverpool Telescope and MOPTOP are shown to be ideally situated to expand the literature dataset of PHA polarimetry. The sample of objects observed in this study makes a significant contribution to the existing sample of PHAs studied with high-phase angle polarimetry. Our observation of asteroid 2023 BU was notable in several regards: it made one of the closest recorded approaches ever of an asteroid to Earth without impact (0.03 Lunar Distances), and we believe it to be one of the smallest asteroids ever to be measured with polarimetry. The LT and MOPTOP’s capability to perform spectropolarimetry was also tested, and it was found that 2015 RN35 may have an unusually high porosity.

(469219) Kamo`oalewa is a small near-Earth asteroid, which is currently a quasi-satellite of Earth. Lightcurve measurements revealed a rotation period of about 30 minutes, while the spectrum is compatible with that of S-type asteroids. This object has been selected as the target of the sample-return Tianwen-2 mission of the China National Space Administration.

In early 2024, we performed an observational campaign to better determine the orbit of Kamo`oalewa. Astrometric measurements were taken from the Loiano Astronomical Station and from the Calar Alto Observatory. We also accurately re-measured two precovery detections from the Sloan Digital Sky Survey from 2004. This new astrometry was used in a 7-dimensional orbit determination, aimed at determining both the orbital elements and the Yarkovsky effect. This process was performed with the Aegis software [1] of the ESA NEO Coordination Centre. We detected a semi-major axis drift due to the Yarkovsky effect of -68.96 ± 3.9 au/My, with a high signal-to-noise of 17.5. The new orbit solution also significantly reduced the position uncertainty at the time of arrival of the Tianwen-2 spacecraft.

Thermal inertia is then studied by using ASTERIA [2], a new method suitable to estimate the thermal properties of small asteroids affected by the Yarkovsky effect. By using different models for the physical parameters of Kamo`oalewa, the ASTERIA model estimated the thermal inertia at $155^{+90}_{-45}$ J m$^{-2}$ K$^{-1}$ s$^{-1/2}$ or at $181^{+99}_{-60}$ J m$^{-2}$ K$^{-1}$ s$^{-1/2}$. Assuming that the low thermal inertia is given by the presence of a regolith layer on the surface, thermal conductivity models [3] predict a grain size of the order of 0.1 – 3 mm.

[1] Fenucci et al. (2024), The Aegis orbit determination and impact monitoring system and services of the NEOCC web portal, CMDA, 136, 58
[2] Novaković et al. (2024), ASTERIA – Asteroid Thermal Inertia Analyzer, PSJ, 5, 1
[3] Gundlach and Blum (2013), A new method to determine the grain size of planetary regolith, Icarus, 223, 1

Introduction: After the successful launch of the ESA/HERA mission [1] on 7 October 2024 it is timely to recall what we have learned from The NASA Double Asteroid Redirection Test (DART) impact [2] and ASI/Light Italian Cubesat for Imaging of Asteroids (LICIACube) [3] mission. DART was the first space mission that successfully demonstrated the kinetic impactor technique for planetary defense. It was at the same instant, on 26th September 2022, when LICIACube [3] evidenced the impact and became the first Cubesat to image the plume coming from Dimorphos. Among the scientific objectives of the HERA mission is to determine the physical properties of Dimorphos, including its internal structure and to constrain binary formation scenarios. Here we present how dust dynamics simulations with LICIACube observations can help constraining the physical properties of the dust in the binary system.
The scientific objectives: The estimation of the size distribution and velocity distribution of the plume in close vicinity to Dimorphos, captured in the LICIACube images is still an unanswered question. We attempt to constrain the particle sizes within the collimated plume structures and address questions such as: what is the effect of motion of the dust clumps with different dust composition of different fragments? What are the optical properties of the dust with different dust composition of different fragments?
The model: We apply the 3D+t model – LIMARDE [4,5] constrained with laboratory observations [6], impact simulations and near- field observations such as the LICIACube [7] images and simulates the long -lived ejecta. The model computes single particle trajectories, the dust rotational frequencies and velocity as well as the particle orientation at any time and distance. We compute the dust velocity distribution based on the physical properties (size, mass and shape) derived from the LICIACube observations. The results are useful to check what is the role of the fragmentation of the particles and to constrain the physical properties based on the dynamical properties of the ejected dust in the near- and mid- environment.
Discussion: The LICIACube observations suggest that we have the locations of accumulation of different particles along the collimated plume streamers. The latter may contain particles of the same density and shape but with different velocity and rotation due to the initial ejected position and form not-linear motion within the collimated filament – like structures. Our LIMARDE simulations with particles of different shapes show that result with different velocities suggest a scenario where the dusty clumps could occur at the same location due to motion of particles with different shapes. We address what is the effect of non-sphericity on the dust deposition distribution of the ejecta plume and the influence of the dust temperature, initial orientation, and initial rotational energy on the ejecta evolution.

References: [1] Michel, P. et al. 2022 PSJ 160 [2] Rivkin, A.S. et al. 2021, PSJ, 2, 24pp; [3] Dotto, E. et al. 2021, PSS 199, [4] Ivanovski et al. 2023, u.rev.; [5] Fahnestock et al. 2022, PSJ; [6] Ormo et al. 2022, E&PSL [7] Dotto et al. 2024, Nature

Near-Earth objects provide a considerable risk to mankind. To comprehend the issue and safeguard our planet, it is essential to monitor and advance technologies to alleviate the risk. NEOs are mineral-rich and potentially provide fresh resources for future space research missions. Monitoring Near-Earth Objects (NEOs) may enhance our understanding of solar system origin as well.
By analyzing and characterizing NEO, we may anticipate the effect and mitigate the repercussions. Larger NEOs provide a higher hazard, but smaller NEOs are more prevalent and have considerable influence. It was believed that small NEOs disintegrate while entering the atmosphere, the chelyabinsk meteor of size around 18m proves we need to work more in detecting small NEOs. We have around 34,000 known near earth asteroids and over 120 comets still the work is far from done.
While our ground based telescopes and radars have proven success in the past, their restricted sensitivity due to climate and weather conditions and other technological restrictions makes space based technology a crucial need. With the introduction of Infrared astronomical satellite (IRAS), a joint project by NASA,UK science and research council and netherland space agency in 1986 we were able to scan 96% of our sky and also understood the importance of space based telescopes for NEOs detections. Though the telescope provides necessary support we have to consider factors like cost,scalability and potential risk of space debris and sensitivity of the instrument.
The technology of small satellites provide a good alternative to these giant space based telescopes. The project focuses on design and optimisation of small sat constellations specifically dedicated for detections and characterization of near earth objects, aiming to tackle technical challenges and potential future development. The project also emphasizes on the limitations of current ground based telescopes and radar and concentrates on optimizing and integrating their effects with small satellites.Where our major focus is on designing and optimizing the tech we have also included the constraints with cost and scalability and issues related to quick deployment while mitigating the risks associated with rising space debris and collision avoidance. The project also focuses on analyzing prior flyby missions and proposing appropriate modifications to improve research effect and enhance understanding of NEOs.
The initiative encompasses planetary defense strategy to govern operations and enhance global corporations including responsibilities of private stakeholders.

In this work, we apply jet transport techniques as implemented in the open-source software package NEOs.jl [1, 2] to the problem of orbit determination and impact probability predictions for asteroid 2024 PDC25, the hypothetical scenario for the 9th Planetary Defense Conference 2025. From the astrometry file available for 2024 PDC25 at Epoch 1 [3], we perform a preliminary orbit determination using only
observations from the first three nights available in the file. We then perform an orbit determination to the full astrometry dataset until Epoch 1, taking as initial guess the output from the preliminary orbit
determination step. We use the latter orbital fit to propagate the asteroid region of uncertainty until its close approach to the Earth in 2041. Finally, we provide impact probability figures for the close approach to the Earth in 2041, and assess how observations in August 2025 will affect these predictions.

References
[1] J. A. Pérez-Hernández, Dynamics of Near-Earth objects: the Yarkovsky effect for asteroid Apophis and the Lyapunov spec-
trum of Halley’s comet, Ph.D. thesis, Universidad Nacional Autónoma de México, 2021.
[2] J. A. Pérez-Hernández, L. E. Ramírez-Montoya, L. Benet, NEOs.jl: v0.11.0. URL: https://github.com/PerezHz/NEOs.jl, 2024.
[3] CNEOS NASA-JPL, Asteroid 2024 PDC25 astrometry file, https://cneos.jpl.nasa.gov/pd/cs/pdc25/2024pdc25.xml, 2024. Accessed: 2024-12-15.

The IRAC camera on the Spitzer Space Telescope observed 2175 Near Earth Objects (NEOs) during its Warm Mission phase, across three large surveys and a small number of dedicated small projects. We present the final reprocessing of the NEO data and infrared photometry in the 3.6 μ and 4.5 μ regimes [1]. The window of observation has allowed for a small number of complete light curves to be constructed along with a greater number of partial light curves. For the 43 objects for which we have full light curves we determine period and amplitude. Additionally we use the full sample of partial light curves to update our estimated shape distribution for Near Earth Objects from prior studies [2] for better comparison with upcoming work to determine the shape distribution of main-belt asteroids of similar size. By combining Spitzer infrared photometry with optical photometry from PanSTARRS we also present improved albedo and diameter estimates (Figure 1) for objects observed during the same period using the Near-Earth Asteroid Thermal Model (NEATM) [3].

For those 19 objects with diameters greater than 200m and whose light curves display significant amplitude and/or “super-fast” rotation (P < 2.2 h) we derive the minimum cohesive strength required for these objects to resist rotational fission - an example light curve for one such object is given as Figure 2. Most of these results fall in the tens to hundreds of Pascals range which is in keeping with previous studies [4] but we report a significantly larger strength for the potentially hazardous asteroid 2002 TW55 suggesting an increased likelihood that the object is monolithic rather than an aggregate. These results are of great relevance to planetary defense as shape, strength, size and spin are key parameters when planning defense measures.

Asteroids with sizes below a few km are mostly believed to be loose aggregates bound together primarily by self-gravity, known as rubble-piles. Historically, rubble-pile asteroids have been treated as essentially cohesionless aggregates. Recent evidence from high-resolution spacecraft in-situ observations (e.g. Hayabusa2 and OSIRIS-REx missions) show very low values for cohesion on the surface and in the body [1]. However, the physical nature and intensity of inter-particle interaction forces remain unclear, therefore, their effect on the macroscopic properties is not well understood. For example, the mechanical properties of rubble-pile regolith and individual constituents (microscopic or particle scale properties) could be different between its surface and subsurface layers, possibly influencing the aggregates response to natural or artificial impacts and high spin rates [e.g. 2].
In this study, we investigate how the variation of particle-scale properties affect the macroscopic behavior of rubble-pile asteroids by simulating layered rubble-piles using GRAINS [e.g. 3, 4]. GRAINS is an N-body Discrete Element Method (DEM) code designed for simulating the behavior of granular materials in rubble-pile asteroids and can model individual particles as irregular shapes instead of spheres. Following [5], we model a layered rubble-pile asteroid (see Fig. 1) where the microscopic properties of the surface layer and the core are characterized by distinct mechanical parameters (such as cohesion, friction, and density). We vary those mechanical parameters, analyze the resulting stability of the aggregate, calculate macroscopic properties (such as their tensile strength), and compare these results with observations and experimental findings [e.g. 1, 6].
Understanding the mechanical properties and evolution of rubble-pile asteroids is crucial for both their scientific and technological exploitation, including the effective design of planetary defense strategies. The approach proposed here offers predictive insights and characterization of layered rubble-pile asteroids and provides a framework for interpreting in-situ observations, including upcoming Hera related
investigations on the post-DART state of the Didymos binary.
Acknowledgement
Funded by the European Union (ERC, TRACES, 101077758). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council. Neither the European Union nor the granting authority can be held responsible for them.

At the time of writing this abstract, eleven asteroids had been discovered in the sky prior to their impact on Earth. The first one was detected in 2008, but in 2024 alone, four were discovered. This shows that the number of detection is steadily increasing, and we should expect this trend to continue in the coming years with the ongoing improvement of observational techniques and the development of new surveys dedicated to planetary defense, such as the Flyeye telescopes [1, 2].

The detection and analysis of imminent impactors are critical for planetary defense. We present here a new processing pipeline to extract accurate flux measurements from trailed observations of fast-moving near-Earth objects. This method was developed to address the observational challenges inherent from the characteristics of small impactors. Indeed, these objects are generally small (and thus faint), become bright only when they are close to Earth (and thus move very fast across the sky), rotate very quickly (due to their small size), and have poorly characterized orbits at the time of observation.

Our new approach consists of observing NEOs using sidereal tracking and long exposures. The asteroid moves accross the field of view and appears as a trail, while background stars remain sharp. This allows for precise astrometric and photometric calibration using standard circular apertures for the stars, while photometric data from the asteroid’s trail are extracted using rectangular apertures. The flux from the object can then be extracted along the trail, using ephemeris information for time calibration.

Using this method we analyzed the lightcurve of several imminent impactors (2022 EB5, 2023 CX1, 2024 BX1, 2024 RW1, 2024 XA1) and found that they usually rotate very quickly, with rotation periods shorter than any other objects in the solar system.
In this talk we will review the trail observation technique and analysis [the method was published here 3] and discuss the results found for these imminent impactors. We will also highlight what lightcurve information can reveal about the physical characterization of these objects and their relevance to planetary defense.

[1] A.DiCecco, G.Bianco, C.Marzo, M.C.Falvella, E.Perozzi, D.Iacovone, Commissioning and science verification options for the esa fly-eye neo survey telescope, 43rd COSPAR Scientific Assembly. Held 28 January-4 February 43 (2021) 327.
[2] C. Arcidiacono, M. Simioni, R. Ragazzoni, P. Gregori, P. Lorenzi, F. Cerutti, R. Ziano, M. Bisiani, R. Pellegrini, A. Guazzora, S. Pieri, M. Dima, S. D. Rosa, S. Zaggia, J. Farinato, D. Magrin, A. Grazian, M. Gullieuszik, FlyEye ground-based telescope: Unveiling new frontiers in astronomical science, in: Ground-Based and Airborne Instrumentation for Astronomy X, volume 13096, SPIE, 2024, pp. 3489–3497.
[3] M. Devogèle, L. Buzzi, M. Micheli, J. L. Cano, L. Conversi, E. Jehin, M. Ferrais, F. Ocan ̃a, D. Föhring, C. Drury, Z. Benkhaldoun, P. Jenniskens, Aperture photometry on asteroid trails: Detection of the fastest-rotating near-Earth object, 689 (2024) A211.

The near-Earth binary asteroid (65803) Didymos gained significant scientific attention after the successful impact of NASA's DART mission on its secondary, Dimorphos, validating kinetic impact as a planetary defence strategy (Thomas et al., 2023). This study builds on previous analyses of particle dynamics on Didymos' surface (Trogolo et al.,2023). Using updated physical parameters (Naidu et al., 2024) and a high resolution shape model (Daly et al., 2024), we investigate material lift-off induced by its rapid rotation and mass transference to the secondary.

We assess the asteroid's surface stability by exploring a range of mass and asteroid extents using the reported values, along with their corresponding uncertainties. A total of 25 combinations of mass and volume values were analyzed using numerical simulations, investigating the trajectories and final states of the ejected particles. Four distinct outcomes were identified: reimpact on Didymos (ES1), particles remaining in orbit (ES2), collisions with Dimorphos (ES3), and escape from the system (ES4). Our results show that over 85$\%$ smaller particles ($<$5 $\mu$m radius) quickly return to Didymos, concentrating in equatorial regions, while larger particles ($>$5 cm radius) reach mid-latitudes or higher. Such particles could trigger surface sliding, potentially explaining mass wasting features (Barnouin et al., 2024, Bigot et al., 2024).

Orbiting particles form disk-like structures around Didymos, but absolute density values cannot be derived as they depend on the actual emission mass rate, and may be observationally undetectable. The densest regions are located near 600 meters from the asteroid's center. Over time, solar radiation pressure (SRP) drives smaller particles to form a comet-like tail in the direction opposite to the Sun. Larger particles, less affected by SRP, remain in stable orbits for up to six months. The distribution and dynamics of such particles are the outcome of complex interactions due to Didymos’ irregular shape, fast rotation, and solar radiation pressure.

Material transfer to Dimorphos is also notable, with up to 12$\%$ of the largest particles colliding with its surface at $\sim$ 0.14 m/s, comparable to its escape velocity. Most impacts occur in the trailing hemisphere of Dimorphos, following linear patterns determined by the initial trajectories of the particles.

The ESA Hera mission (Michel et al., 2022), accompanied by the Milani CubeSat carrying the VISTA instrument (Gisellu et al., 2023), will offer a unique opportunity to detect dust particles and volatile materials in the Didymos system. VISTA’s ability to measure particles as small as 10 $\mu$m will be crucial for validating our prediction of dust production and the persistence of fine material in the system's environment. Given the short survival time of fine material, any dust detected by VISTA would support the take-off and landing processes described in this study. These findings could shed light on the dynamics of loose material on fast-rotating small bodies and the interaction between binary asteroid components, enhancing our understanding of resurfacing and orbital processes in binary asteroid systems.

The successful demonstration of NASA DART mission success in testing the kinetic impact as a planetary defense technique will be enhanced even more by the scientific observations of the upcoming ESA Hera mission. The spacecraft, launched on October 2024, and now on his way to the Didymos-Dimorphos binary asteroid system, will understand in detail the effect of the DART impact and the outcome of the first planetary defense mission ever. Moreover, en route to its target, the Hera spacecraft will perform in March a close fly-by of Mars and its moon Deimos increasing the scientific outcome of the mission.
In the study of laboratory analogs of mission targets, the grain size is a critical factor for understanding regolith, dust and fragmented rocks covering solid planetary sur-faces such as asteroids. Its presence affects key physical properties that are crucial for interpreting remote sensing observation, such as: albedo, thermal conductivity, surface roughness, and spectroscopic properties. Since our understanding of complex samples with varying grain sizes remains incomplete, we conducted several laboratory experiments to deepen our knowledge on the topic. Our analog sample preparation benefits of a new protocol we developed to effectively select grains to hyperfine size, cleaning bigger grains from small grain size contaminations, and mix several components with different grain sizes, assuring homogenization while preserving the initial grain size distribution. This study investigates a wide spectral range from near-infrared (NIR) to mid-infrared (MIR) to support a large number of instruments on board the Hera spacecraft.
One of the most intriguing findings is the observed shift in slope trends caused by the addition of dark material. Specifically, we observed an inversion between reddening and bluing effects, depending on both the composition of the mixture and the grain size of the components. Additionally, we examined several key features, including the hydration band at 2.7 μm, the Reststrahlen band and the Transparency feature.
This study highlights the importance of laboratory measurements on planetary rocky analogs in bridging the gap between the physical properties of these materials and remote sensing data obtained from ground-based telescopes, space telescopes, or spacecraft missions. Indeed, silicate asteroids, like Didymos, are known for their rocky composition, and they are a fascinating focus of space exploration, providing insights into the primordial materials that shaped our Solar System. Moreover, as asteroids in general, should be monitored for the possible threat posed to terrestrial life in the event of an Earth impact and our results will be useful also for the upcoming Apophis close approach in 2029.

The analysis of mm-wavelength thermal emission from near-Earth asteroids can be used to constrain thermophysical (thermal inertia, emissivity) and radiative (index of refraction, loss tangent) properties of the top few centimeters of regolith. These properties can be used to constrain the regolith porosity. For near-Earth asteroids (NEAs), regolith porosity is one of the physical properties that must be known for the development of impact risk mitigation missions [1].

Here we present a framework, based on [2], that combines thermal, radiative transfer, and regolith thermophysical models that can be compared to observed passive mm-wave thermal emission from ground observations. The thermal model used is KRC [3], the radiative transfer model is that used by [2], and the regolith thermophysical model is based on [4].

This approach requires a priori knowledge of the object’s composition, Bond albedo, shape, size, orbit, and spin properties. Comparisons of outputs from the series of models to observations provide best-fit estimates of thermal inertia, index of refraction, loss tangent, and effective emissivity. These best-fit solutions are then used to estimate surficial density, porosity, and effective grain size.

The first observations from a recent thermal survey of NEAs, aimed at acquiring data from up to 15 targets per year using mm and sub-mm facilities (ALMA, IRAM, SMA, VLA), are now available for analysis. Observations of targets acquired include (1685) Toro, 2005 EK70, 2015 DE198, 2013 NK4, 2011 UL21, 2024 ON, (1036) Ganymede, (4954) Eric, and 2006 WB. Archival observations of Dimorphos/Didymos and 1998 QE2 are also available. Observations of these objects provide an opportunity to demonstrate the thermophysical-radiative transfer modeling approach to determine regolith porosities of NEAs. Results will be presented at the conference.

Acknowledgements and disclaimers:
This research program is supported through NASA ROSES Near-Earth Object Observations program grant 23-YORPD23_2-0034. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

References:

[1] Levasseur-Regourd, A., Chantal, Hadamcik, E., Lasue, J., 2006, Advances in Space Research, 37(1), p. 161–168.

[2] Li, J-Y, Moullet, A, Titus, T, N., Hsieh, H. H., Sykes, M. V., 2020, Disk-integrated Thermal Properties of Ceres Measured at Millimeter Wavelengths, The Astronomical Journal, 159(5), id.215, 9 p.

[3] Kieffer, H., 2013, Thermal model for analysis of Mars infrared mapping, Journal of Geophysical Research: Planets, 118(3), pp. 451–470.

[4] MacLennan, E., & Emery, J., 2022, Thermophysical Investigation of Asteroid Surfaces. II. Factors Influencing Grain Size, Planet. Sci. J.,3(2), 47 p. 47.

Keywords: NEOs, NEAs, Near Earth Space

Decameter size NEAs are of particular interest in the context of the NEO problem because the frequency of collisions with such bodies is much higher than that of larger bodies and the consequences of collisions can be still significant. So far, the population of decameter bodies has been poorly studied since they are difficult to observe. To build an efficient system for detecting and monitoring such bodies it is necessary to estimate their distribution in near-Earth space (NES). We present the results of statistical modeling of NEA entries into NES which is a sphere with a radius of 0.01 au around the Earth.

We considered the dynamic evolution of the NEAs over some dozens of typical periods of the NEAs, fixing every entry into the NES. The NEA population was modeled using the NEOMOD package and integrated for 100 years using the REBOUND package.

The main results are: 1) the frequency of entries of NEAs larger than 10 m is approximately 1000 per year (as lower limit); 2) up to half of the NEAs enter the NES from day-time-hemisphere; 3) there is anisotropy in the flux density of incoming asteroids. 4) typical velocity of approach to the Earth at the distance of 0.01 au is approximately 7.5 km/s (maximum speed can reach up to 30 km/s). 5) the anisotropy decreases when considering a near-Earth sphere of a smaller size. For the Earth atmosphere the frequency of entries is qualitatively consistent with the data of frequency of bolide phenomena recorded using satellites (according to NASA).

The Planetary Science Team at the University of Alicante (Spain) is currently formed by 10 researchers dedicated to modeling and physical characterization of small bodies in the Solar System. Here are some current topics:

\textbf{IEO Survey}: Currently, 34 objects have an Interior Earth Orbit (IEO) that don't pose an immediate risk but may eventually lead to Earth-crossing trajectories due to close encounters with Mercury and Venus\cite{delafuente2021}. Identifying these objects while they still have an IEO is crucial for detecting potential future threats. Major surveys can't detect them due to the need for observations at low solar elongations during twilight\cite{delafuente2019}. To address this, we’ve launched two parallel twilight surveys using the TFRM telescope in Montsec in Catalonia, Spain (Northern Hemisphere) and the Springbok telescope in Namibia (Southern Hemisphere).

\textbf{Analysis of surface features}: The different internal structures of an asteroid influence how different small-bodies form and evolve and how different geomorphologies occur on their surfaces \cite{Buczkowski2008}. Consequently, a way of characterizing the interiors of asteroids is based on interpretation of the external properties of their surfaces \cite{Scheeres2015}. We map, analyze, and compare different surface features (e.g.,\ boulders, fractures, cracks, lineaments, pits chains, impact craters, etc.) to continuously explore the geological evolution of each body \cite{Barnouin2024} and the correlation of such features with their physical properties.

\textbf{Boulder-reaccumulation in the Didymos System following from the DART impact \cite{Daly2023}}: The upcoming Hera mission \cite{Michel2018} will characterize the surfaces of the two bodies that comprise the Didymos system in great detail after its rendezvous near the end of 2026. The effects of low-speed impacting boulders may be evident in what will be observed. Using a soft-sphere discrete element method (SSDEM) contact model \cite{Cundall1979} included by \citet{Schwartz2012} in the \textit{n}-body software package \texttt{pkdgrav} \cite{Stadel2001,Richardson2000}, we are analyzing the mechanics of these secondary impacts and the post-DART implications they may have on the surfaces of Dimorphos and Didymos.

\textbf{Determining the Physical Parameters of NEOs}: To characterize the physical parameters of Earth-bound Near-Earth Objects (NEOs), we utilize a variety of data sources, including light curves, radar observations, sparse photometry from surveys, and measurements from the Gaia mission. The SAGE method \cite{2018MNRAS.473.5050B} and the SHAPE model \cite{2007Icar..186..152M} have been employed to analyze these data. Additionally, we account for the correction of the photocenter relative to the center of mass in order to refine orbital parameters and assess the Yarkovsky effect and bulk density.

\textbf{Fast gravity computation and surface stability analysis}: We have developed a Fast Fourier Transform (FFT) based method for an extremely fast and accurate computation of the gravitational field in any space region about a body with any shape and mass distribution. We are modeling the shape and stability on the surface of different asteroids using super-ellipsoids.
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Other topics studied in our group are summarized in this conference by contributions: (1) Liu, P.-Y., et al.\ “Collisional Spin-Up of Asteroids: Alternative Mechanisms of Binary Asteroid Formation Independent of YORP Effects,” and (2) Trogolo, N., et al.\ “Mass ejection by fast-spinning Didymos: orbiting dust and transference to Dimorphos.”

Near-Earth asteroids (NEAs) provide valuable opportunities to study the physical and structural properties of small bodies. While most asteroids have rotation periods longer than the "cohesionless spin barrier"—a 2.2-hour limit beyond which rubble-pile asteroids would break apart due to centrifugal forces—some rotate much faster, challenging current understanding of the internal structure of these objects.
Detecting short rotation periods in NEAs is particularly challenging because of the difficulty of obtaining continuous, high-cadence observations of multiple targets over several hours. Large-scale surveys are not typically designed to capture the dense temporal sampling needed to fully resolve the light curves of fast rotators. These limitations highlight the importance of follow-up observations with dedicated telescopes to obtain high temporal resolution photometric data.

In this work we present the current status of an ongoing survey designed to expand the sample of NEAs with well-determined rotation periods, focusing on asteroids with absolute magnitudes H$>$22.5. The survey uses four newly installed robotic telescopes at the Teide Observatory in Tenerife, Canary Islands. These include a pair of 80-cm telescopes (TTT1-2), a 1-m wide-field telescope (TST) with a field of view of 4.1 deg$^2$, and a newly installed 2-m telescope (TTT-3). All are equipped with sCMOS imaging sensors that provide the high temporal resolution required for photometric observations, making them ideal for detecting and studying fast rotators.
Our survey targets recently discovered small NEAs with unknown rotation periods. By studying their rotational states, we aim to gain deeper insights into the forces and mechanisms that allow these bodies to maintain their structural integrity at high rotation rates, with important implications for planetary defense strategies and future research on asteroid composition and the physical processes driving their internal evolution.

To date, over fifty NEAs have been observed in the days following their discovery to identify and analyze short rotation periods. We will present preliminary results, highlighting several objects for which we have clearly determined rotation periods, including examples of fast rotators (see Fig. 1).
In addition, we will present GPUPHOT, a new photometry software package optimized for fast and efficient image processing. GPUPHOT integrates a novel set of convolution-based algorithms that significantly improve the performance of point source photometry. Designed to support the large data requirements of robotic telescopes, the software will be made publicly available later this year, providing valuable resources to the planetary science community.

Asteroids with MOID less than 1 AU are of significant scientific interest due to their potential for close approaches to Earth's orbit. Characterizing their physical properties—size, shape, and spin state—provides essential insights into their evolution, taxonomic classification, and potential impact threat.

In this work, we present a thorough analysis of the absolute magnitude and slope parameters $G_1$ and $G_2$, rotation period, shape and pole direction of thirteen asteroids with MOID less than 1 AU, including 2789, 2817, 3173, 3392, 2459, 3473 and 3716. We have obtained their rotation period with high precision with an error of less than 0.5\% error with light curve analysis (Pravec et al. 2000). From phase curve analysis, we obtain absolute magnitude and slope parameter measurements (Muinonen et al. 2010), where we integrate observations from multiple observatories and wavelength bands, correcting for biases introduced by each source. For most of the asteroids, we also obtain their first models of the shape and pole direction from light curve inversion (Kaasalainen et al. 2001).

These parameters provide vital insights into object size, taxonomic classification, mass distribution, and angular momentum balance. Such knowledge is essential for developing effective strategies to alter an NEO’s trajectory, should the need arise (Sánchez \& Scheeres, 2012). The obtained methods and results can be further extended to NEO and Potentially Hazardous Asteroids (PHAs), which can improve planning for potential mitigation missions.

• Pravec, P. and Harris, A.W., 2000. Fast and slow rotation of asteroids. Icarus, 148(1), pp.12-20.
• Muinonen, K., Belskaya, I.N., Cellino, A., Delbò, M., Levasseur-Regourd, A.C., Penttilä, A. and Tedesco, E.F., 2010. A three-parameter magnitude phase function for asteroids. Icarus, 209(2), pp.542-555.
• Kaasalainen, M., Torppa, J. and Muinonen, K., 2001. Optimization methods for asteroid lightcurve inversion: II. The complete inverse problem. Icarus, 153(1), pp.37-51.
• Sánchez, D.P. and Scheeres, D.J., 2012. DEM simulation of rotation-induced reshaping and disruption of rubble-pile asteroids. Icarus, 218(2), pp.876-894.

We present the use of the University of Tasmania's (UTAS) optical and radio telescopes to conduct observations of near-Earth objects from 2021 to 2024. The Canberra Deep Space Communications Complex transmitted at 7159.45 MHz, with the radar echo detected by the UTAS radio telescopes. The method of accounting for the Doppler shift between the stations and the near-Earth object will be described so as others could implement a similar program. We share our results, with confirmed detections of 1994 PC1 using the Hobart and Katherine 12m antennas, 2003 UC20 and 2024 MK with the Hobart 12m antenna, demonstrating the feasibility of using small radio telescopes for these observations. Data collected from other observatories, such as Tidbinbilla, as well as UTAS radar tracking of the moon, will also be presented in the context of demonstrating the means of applying these Doppler corrections and the accuracy of each method. Optical observations conducted in this period will also be detailed, as they complement radar observations and aid in refining the orbit parameters. Furthermore, in 2024 we have incorporated observations with optical telescopes to broader the scope of our measurements in the context for planetary defense.

Keywords: Near-Earth Objects, Radar, radio telescopes, binary asteroid

From 2019 to 2022, the ESA funded the “NEO Observation Concepts for Radar Systems” pilot project, aimed at the future development of a European radar system for NEOs, enhancing planetary defense, mission planning, and advancing the scientific study of Near-Earth Objects. Contributions from INAF, SpaceDyS, and the University of Helsinki led to successful radar campaigns, observing asteroids such as 2021 AF8 and (4660) Nereus, conducted in collaboration with NASA’s Deep Space Network and the Jet Propulsion Laboratory, California Institute of Technology. The main results of this project are presented in [1].

Additional radar observations were performed to demonstrate the capabilities of radio telescopes and enhance our expertise in this field. We also developed specific software tools for asteroid radar
observations that played a critical role in these advancements. This work highlights the results of some of these observations, with a focus on those carried out on the asteroids 2005 LW3 in 2022 and 2006
WB in 2024.

The 2005 LW3 observation involved a multi-static radar configuration formed by the 70-m DSS-63 antenna at the Madrid Deep Space Communications Complex (MDSCC) as the transmitter, and the 32-m Medicina ”G. Grueff” and the 100-m Effelsberg radio telescopes as receivers, marking one of the first radar observations of a NEO conducted exclusively using facilities in Europe.

The experiment was carried out on November 23, 2022, during the asteroid’s close approach to Earth. Both receiving stations successfully detected radar echoes, achieving high-frequency resolution.

We derived key physical characteristics of 2005 LW3, such as the rotation period and the polarization ratio, the latter related to the roughness of the asteroid’s surface and sub-surface at the wavelength scale.

Delay-Doppler imaging conducted by Goldstone revealed that the asteroid measures about 400 meters in diameter and has a satellite approximately 50-100 meters in diameter. A significant achievement of our observations was the independent confirmation of the satellite, detected as a distinct spectral spike superimposed on the primary body’s broader radar echo.

Finally, we present the preliminary results from the last radar observation of asteroid 2006 WB, conducted on November 25-26, 2024, during its close approach. This campaign employed the 64-m Sardinia Radio Telescope (SRT/SDSA) as a receiver, using different acquisition systems - some of which are under testing. The Goldstone DSS-14 and Madrid DSS-63 antennas were the involved transmitters, respectively at frequencies of about 8.6 and 7.2 GHz. These observations provided important information on the physical parameters of the target. The 8-GHz portion of the experiment also aimed at allowing us to test, for the first time, the production of Delay-Doppler images. Reduction is still underway.

Collectively, these findings demonstrate the potential of the European radio telescopes for an EU- based radar system, in synergy and collaboration with the US one, to contribute significantly to NEO characterization and planetary defense efforts.

Meteoroids are the solid remnants of asteroids and comets, ranging from micrometres to decametres in size. Upon entering Earth’s atmosphere, they follow a ballistic trajectory that is partly determined by their composition and internal structure. They display a variety of behaviours including harmless disintegration, meteorite deposition (e.g: Nqweba), explosive airbursts (e.g: Chelyabinsk), or even cratering. Understanding the spatial and temporal distribution of meteoroid falls, as well as their potential consequences, is a matter of global safety and security. Unfortunately, compositional and structural information is difficult to gather without physically collecting fallen meteorites, which represent only the toughest fraction of extraterrestrial intruders. This study proposes novel methods to characterise all the material that enters our atmosphere, whether it can be collected or not.

Falling meteoroids ignite and radiate visible light in response to intense ram pressure, rendering them visible to ground-based fireball camera networks across the globe. These networks include the Global Meteor Network (GMN), the European Fireball Network (EFN), and Australia’s Desert Fireball Network (DFN). When multiple cameras within the same network capture the same burning meteoroid, they can precisely calculate its 3D trajectory and several useful dimensionless parameters. The first is the ballistic coefficient (α), which compares the drag and weight forces upon a falling object. High-α objects are more susceptible to atmospheric deceleration than low-α objects. The second parameter is the mass loss factor (β), which indicates the ease of removing material from a falling meteoroid. High-β objects tend to burn rapidly and are unlikely to survive long enough to deposit fragments upon the ground. As demonstrated by Gritsevich (2009) and Sansom et al (2019), α and β can be determined using only altitude and velocity data, with no required assumptions. The final parameter of interest is the pressure factor (Pf) value formulated by Borovička et al (2022). It depends on estimates of entry mass and maximum ram pressure, and indicates bulk strength. Stony and metallic asteroids produce higher Pf values than icy cometary bodies, for example.

Plotting α, β and Pf values for various falls can enable reasonable estimates of bulk composition and strength of the fallen objects. Subsequently, details of internal structure can be inferred, such as the presence or absence of melt veins, cementing minerals or large pores. We perform a quantitative study of ~150 instrumentally observed falls, including almost 60 meteorites, and dozens of Geminid meteors that originated from 3200 Phaethon. We also examine thousands of simulated meteoroids to investigate links between α, β, composition, structure, and dynamic behaviour. This presentation will summarise preliminary results, with a focus on the compositional and structural features that contribute to hazardous impacts. We will also consider the potential for comprehensive characterisation of all extraterrestrial material that rains upon Earth.

To assess the risk of an impact from a Near Earth Object (NEO), it is crucial to estimate both the size and density of the object. These estimations can be more easily inferred if the albedo of the object is known. In this context, polarization observations are a key tool for swiftly determining the size of a NEO, and consequently, their potential threat to Earth.

The degree of linear polarization is inversely proportional to the albedo of the scattering surface of an asteroid. This relation is better constrained at high phase angles at which NEOs are usually observed and where polarization is more significant. This translates into low albedo objects consistently exhibiting higher degree of polarization compared to high albedo objects.

Thus, polarimetry allows for direct albedo measurement without relying on additional data, such as the absolute magnitude. Also, polarimetry measurements are independent on the shape of the observed object, so we are not affected by the rotational phase at which the object is observed. Consequently, determining albedo through polarimetry serves as a crucial complementary and independent method to thermal modeling.

In this poster, we will present the design of Rapid-Defender, a polarimeter specifically designed to rapidly characterize NEOs to assess their hazard to Earth. This instrument features a double Wollaston prism, enabling simultaneous measurement of two orthogonal light intensities and yielding the degree of polarization in a single observation. This allows for the estimation of an object's albedo and size within minutes. Additionally, a half-wave plate located before the double Wollaston prism would allow to self-calibrate our observations by swapping the ordinary and extra-ordinary beam by rotating the plane of polarization of the incoming light before the Wollaston prism.

This new instrument would allow to reach V ~ 16 mag when located at 1 meter telescopes, leading to the observation of approximately 20 newly discovered NEOs per year.

Keywords: Long Period Comets, Meteor Showers, Early Warning

We describe a software tool that can be used for planning dedicated searches for long-period comets based on the projection of their meteoroid streams against the sky.

Long period comets with orbital periods in the range 250 to 4000 years produce dense enough meteoroid streams to be detected as meteor showers on Earth [1]. Those meteoroid streams gradually disperse over time [2] and that dispersion defines the range of orbits among which the parent come may be found. There are over 200 known meteor showers from long-period comets that pass close enough to Earth orbit to do so [3]. Most of these parent comets have not yet been discovered.

A dedicated search using meteor showers as a guide can increase the warning time between detection of the comet and its potential impact by several years. The most important part of the orbit for such searches is when the comet is on approach to Earth and close enough to be detected in deep searches, but far enough to not already be detected in routine surveys. This limits the search area on the sky and defines a search strategy to detect comets that only rarely visit the inner solar system.

In this presentation, we discuss the physical mechanisms that lead to the dispersion of long period comets over time [4]. We use that insight to better understand the actual dispersion of showers based on the observed orbital elements at Earth. We then calculate the projected dispersion of these streams to define survey areas on the sky that can be targeted in deep searches [5]. We will discuss search strategies and feasibility.

References
[1] P. Jenniskens, D. S. Lauretta, M. C. Towner, S. Heathcote, E. Jehin, T. Hanke, T. Cooper, J. W. Baggaley, J. A. Howell, C. Johannink, M. Breukers, M. Odeh, N. Moskovitz, L. Juneau, T. Beck, M. De Cicco, D. Samuels, S. Rau, J. Albers, P. S. Gural, Meteor showers from known long-period comets, Icarus 365 (2021) id.114469.
[2] S. Pilorz, P. Jenniskens, J. Vaubaillon, Age-dependent orbital dispersion growth of long period comet meteor showers, in:
Asteroids, Comets, Meteors Conference 2023, LPI Contrib. No. 2851, p. 2484.
[3] P. Jenniskens, Atlas of Earth’s Meteor Showers, Elsevier Science, Amsterdam, Netherlands, 2023.
[4] S. Pilorz, P. Jenniskens, Sun close-encounter model of long-period comet and meteoroid orbit stochastic evolution, Icarus (2025) submitted.
[5] S. Hemmelgarn, N. Moskovitz, S. Pilorz, P. Jenniskens, How meteor showers can guide the search for long-period comets, The Planetary Science Journal 5 (2024) 242–253.

Please see attached PDF.

Acknowledgement
Funded by the European Union (ERC, TRACES, 101077758). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council. Neither the European Union nor the granting authority can be held responsible for them.

Keywords: Near-Earth objects, radar observations, radio telescopes
Astronomical radar observations have been used to probe surfaces of all the solid planets and many smaller bodies in the solar system. This led to a growing interest in the use of radar to characterize near-Earth asteroids (NEAs) and determine their orbits more precisely. There
is a three-fold motivation for performing radar observations of asteroids.

First, asteroids represent primitive remnants of the early solar system and characterization of their properties such as shape, rotation state and existence of satellites can provide insights into their evolution and parent populations. Secondly, precise knowledge of asteroid orbits is essential to assess the extent that they might represent impact hazards to the Earth, and finally, they represent targets for spacecraft. Historically, Goldstone and Arecibo planetary radar capabilities have made significant contributions to tracking many asteroids.

However, their coverage has been limited to the northern hemisphere sky and consequently have missed a fraction of NEAs during Earth flybys. To fill the gap, in recent years we have developed and demonstrated a Southern Hemisphere radar capability using the Canberra Deep Space Communication Complex (CDSCC), part of the NASA Deep Space Network (DSN), as transmitters and the Australia Telescope Compact Array (ATCA) and Murriyang, the Parkes 64m Radio Telescope, and more recently University of Tasmania radio telescopes such as Ceduna 30-m dish as receivers. From the start of the project in 2015 to the end of 2024, we have detected a total of 40 near-Earth asteroids. SHARP also provides the option for observing on dates and times when Goldstone can’t, which is going to be even more important during the Goldstone downtime from 2026-2028.

In 2029, Apophis will encounter Earth within 4.9 radii from the Earth surface. Apophis will approach from the south at a declination of about -30 deg, rapidly move past Earth, and then recede at a declination of +17. Apophis will be observed extensively by the Deep Space Network radars at Goldstone and Canberra. Also, SKA-mid will be operational in South Africa by then and be able to receive radar echo from Apophis and contribute to dramatically enhancing asteroid charactering capability.

Abstract
Apollo and ATEN class asteroids representing a hazardous form of deep space debris, are now being routinely monitored and researched from the Southern Hemisphere longitude of Australia. A bistatic radar and optical program developing since 2015, brings together the resources of the Universities of New South Wales, Tasmania, Western Australia, Curtin and Federal agencies CSIRO and NASA JPL.

Anchored by the JPL-NASA Deep Space Network located in Canberra (CDSCC) and the CSIRO Australia Telescope Compact Array (ATCA) at Narrabri, the Australian consortium also brings with it the radio antennas of the University of Tasmania and optical telescopes of the University of New South Wales (UNSW), the University of Western Australia (UWA) and most recently the Desert Fireball Network of Curtin University. Collectively this Australian asteroid monitoring service offers combined radar/optical asteroid astrometry, photometry, detection and atmospheric re-entry monitoring over the Australian geographic region creating a flexible near Earth object (NEO) monitoring system.

Research within the consortium has developed a STEM education capability that scopes asteroid analogue and digital modelling, polarization decomposition, light curve correlation and emerging doppler/delay capabilities to assess asteroid type, shape and spin.

The Southern Hemisphere asteroid research consortium provides a complementary capability to support global planetary protection efforts through the IAWN, most notably by addressing the small, but non-negligible fraction of asteroids that approach from the south. It will also support NEO monitoring efforts in the 2025-27 timeframe, as the northern hemisphere Goldstone Solar System Radar (GSSR) undergoes critical modernization.

Keywords: Near-Earth Objects, Astrometry, Orbit determination
The increasing availability of astrometric data from a wide range of observatories requires a full statistical evaluation of their performances to ensure reliable orbit determination for small bodies, particularly Near-Earth Objects (NEOs). This study presents a systematic statistical analysis of astrometric post-fit residuals for more than 2,500 observatory codes available from Minor Planet Center (MPC)
https://minorplanetcenter.net/iau/lists/ObsCodesF.html.

The MPC, which operates at the Smithsonian Astrophysical Observatory (SAO), collects and provides astrometric observations of small Solar System bodies, including asteroids, comets, and NEOs, along with Potentially Hazardous Objects (PHAs). As the primary repository of astrometry, the MPC plays a crucial role for NASA, ESA, and other institutions in facilitating orbital calculations and long-term monitoring of PHAs.

This study leverages the complete set of post-fit residuals for over 450 million observations submitted to the MPC. Using this extensive data set, we evaluate variations in astrometric error distributions caused by factors such as pixel resolution, telescope aperture, object brightness, stellar catalog used for the astrometric reduction of the observations. We mostly focused on the performance of various survey telescopes, as they contribute the most to the astrometric data.

We conducted a statistical analysis of the post-fit residuals for these surveys. When uncertainty estimates were available, we compared
our results with the submitted uncertainties, providing an additional layer of validation and information on the quality of their reported data. This method has already proven quite useful, for example in the case of the TESS observations.
The MPC published more than 30 million TESS observations over the past couple of years. During a preliminary analysis performed on TESS observations, a bias was identified in the post-fit residuals,
probably due to timing errors, as shown in Fig. 1. Thanks to the result of this analysis, it was possible to fix the bug and to improve the quality of the observations.

These results advance the characterization of uncertainties for ground- and space-based telescopes and create a new approach for improving future orbit determination methodologies.

The powerful method of stellar occultations is an unbeatable technique uniquely approaching, in some aspects, the performances of planetary space missions. It allows to derive, from ground using small aperture telescopes, asteroids' positions at Gaia-level accuracy [F22], thus extending the time- coverage of Gaia ESA mission. Moreover, it allows to determine the physical size of these objects and probe their environ looking for satellites.
Finally, successful stellar occultation campaigns rely heavily on good networks of citizen scientists across the Globe.

Recently, both DART (NASA) and Hera (ESA) planetary defence missions have shown successful inter-agency, and even agency-industry collaborations when it comes to planetary defence.

In this talk, we present the important contribution of citizen scientists across the globe to support planetary science and planetary defence missions through the orbital (astrometry) and physical (size, shape) characterisation, e.g. Apophis and Didymos. Moreover, we go over some lessons learnt from organising campaigns for occultations by sub-km sized objects, such as Apophis [D23, S23], and the Didymos-Dimorphos system [D23, M24, and abstract 115 by Chesley et al. PDC 2025].

References
[F22] Ferreira, J.F., Tanga, P., Spoto, F., Machado, P., and Herald, D.: 2022, Astronomy and Astrophysics, 658, A73. doi:10.1051/0004-6361/202141753.
[S23] Souami, D., Desmars, J., Tanga, P., Tsiganis, K., de Pater, I., Hsu, Y.M., and, ...: 2023, Asteroids, Comets, Meteors Conference, 2851, 2099.
[D23] Desmars, J., Souami, D., Vavilov, D., Hsu, H.M., De Pater, I., and Hestroffer, D.: 2023, Asteroids, Comets, Meteors Conference, {\bf 2851}, 2376.
[M24] Makadia, R., Chesley, S.R., Farnocchia, D., Naidu, S.P., Souami, D., Tanga, P., and, ...: 2024, The Planetary Science Journal 5, 38. doi:10.3847/PSJ/ad1bce.

The Near-Earth Objects Coordination Centre (NEOCC) is the main component of the Planetary Defence Office (PDO) within ESA's Space Safety Programme. Its mission is to support and coordinate the observations of small Solar System bodies and to assess and track the threats they may pose to Earth. Central to this mission is Aegis (1), an automated orbit determination and impact monitoring system developed by SpaceDyS s.r.l. under ESA contract and operated by NEOCC.

Aegis operates on an hourly basis, continuously downloading new astrometric data from the Minor Planet Center. It relies primarily on two components: orbit determination and impact monitoring. The orbit determination component maintains a dynamic catalogue of near-Earth asteroids, which includes orbital parameters with associated uncertainties, physical properties, residuals, close approaches, and ephemerides. The impact monitoring component computes the impact probabilities of near-Earth asteroids over the next 100 years. Objects with non-zero impact probabilities are listed in the NEOCC Risk List (2). When an object’s impact probability exceeds a certain threshold, Aegis also computes the associated impact corridor, further refining the risk assessment.
This poster will focus on the architectural foundation of the software system, highlighting its infrastructure and deployment. The system is maintained within a structured GitLab repository, enabling efficient version control. An integrated and automatic GitLab pipeline ensures quality assurance by incorporating static code analysis with SonarQube, the generation of Docker images, regression and integration testing, and deployment into pre-operational and operational environments.
The software infrastructure is built on a robust and scalable framework. It employs Docker services for containerization and Redis for handling queues and messages among different services. The infrastructure operates on multiple nodes within ESA’s cloud environment and uses an NFS file system to ensure synchronized and reliable data handling across all nodes. Additionally, REST APIs support internal operations and allow external users to access the system’s data and services. Traefik is implemented as a reverse proxy to efficiently route these requests.
This poster will detail the system’s design and operation, demonstrating how the integration of modern DevOps practices and cloud-based services ensures reliability, scalability, and seamless automation in the continuous monitoring of near-Earth objects.
(1) https://doi.org/10.1007/s10569-024-10225-z
(2) https://neo.ssa.esa.int/risk-list

The binary asteroid (285263)1998 QE2 is one of the largest PHAs known, measuring 3.2km with a 800m satellite, with the last known closest approach to Earth of 0.039 au (~15 lunar distances) on May 31st, 2013. During the 2013 approach, high-resolution radar data was collected at the Arecibo Observatory and Goldstone helping with physical and dynamical characterization of the system. With the radar data, it was possible to obtain a 3D shape model for the primary and an approximate shape model for the moonlet, which is the highest level of information obtainable from radar observations. In this work, the derived shape model and the orbital elements information for the components are used to study the dynamical environment of the system by applying a methodology that is computationally efficient while preserving the accuracy of the model. Multiple asteroid systems can help to understand the formation mechanism and evolution of small bodies in the solar system. Understanding the dynamical environment around these systems could provide clues to the origin and evolution of these bodies and support future space missions.

As Near-Earth Objects (NEOs) continue to present significant risks to planetary safety, advancing asteroid deflection technologies is crucial for strengthening global defense strategies. Traditional methods, such as kinetic impactors and gravity tractors, have demonstrated potential but face challenges related to scalability, precision, and lead-time adaptation. This study introduces an innovative electromagnetic (EM) deflection method that employs dynamically controlled magnetic fields to adjust asteroid trajectories without requiring direct physical contact.

Building on earlier work by Lu and Love, who proposed using gravitational interactions between a spacecraft and an asteroid as a "gravity tractor" for deflection \cite{wie2008dynamics, lu2005gravitational}, this study extends the concept of non-contact deflection to electromagnetic forces. While Coulomb-based electrostatic forces have been explored for similar purposes \cite{gupta2025electrostatic}, their application faces technical challenges, including maintaining stable charge on irregular asteroid surfaces and mitigating arcing under space plasma conditions. The proposed EM method addresses these issues by generating controlled, induced magnetic fields that exert bidirectional forces, allowing for greater precision and operational flexibility.

The electrostatic force between two charges is modeled by Coulomb’s law:

\begin{equation}
F_e = k_e \frac{q_1 q_2}{r^2},
\end{equation}
where $k_e$ is Coulomb’s constant, $q_1$ and $q_2$ are the charges, and $r$ is the distance between them. For comparison, the magnetic force exerted by current-carrying loops or circuits, based on the Biot-Savart Law, is given as:

\begin{equation}
F_m = \frac{\mu_0}{4\pi} \frac{I_1 I_2 l}{d^2},
\end{equation}
where $\mu_0$ is the permeability of free space, $I_1$ and $I_2$ are the currents in the loops, $l$ is their effective length, and $d$ is the distance separating them. These forces, acting over controlled distances, provide the basis for precise trajectory adjustments, which can be scaled and adapted for various asteroid sizes and mission timelines.

This method minimizes fragmentation risks, enhancing mission safety and operational flexibility. Early detection and precise tracking, as demonstrated by the Double Asteroid Redirection Test (DART) \cite{cheng2020dart}, are foundational for implementing timely deflection missions. The potential for this method to deflect hazardous asteroids with limited lead time lies in the scalability of the EM forces, which can be applied progressively, especially in swarm configurations.

\begin{figure}[hbt!]
\begin{center}
\includegraphics[width=0.45\textwidth]{author/figs/period.png}
\caption{Simulation of Apophis' orbital period change over one year under the influence of electrostatic forces from a planetary defense spacecraft (PDS).}
\label{fig: apophis-period}
\end{center}
\end{figure}

A detailed mathematical model and simulations validate the feasibility of the EM deflection method across diverse asteroid masses, sizes, and orbital characteristics. Preliminary results, based on analogous electrostatic force principles, predict a change of approximately 0.0025 seconds in Apophis' orbital period over one year (Figure \ref{fig: apophis-period}). Although modest, this result establishes a baseline for achievable orbital adjustments. Scaling the approach to EM forces is expected to deliver greater control, operational efficiency, and trajectory alterations, especially for larger NEOs detected with limited warning.

A comparative feasibility analysis underscores the advantages of EM deflection over existing methods, including improved cost efficiency, operational flexibility, and precision. Unlike hypervelocity impacts, which risk generating debris fields, EM forces offer a controlled, reversible deflection, reducing fragmentation risks and ensuring mission reliability.

This research positions electromagnetic forces as a transformative addition to planetary defense strategies, addressing critical gaps in current deflection techniques. While early results demonstrate the feasibility of small-scale deflections, ongoing optimization will enhance scalability and adaptability, promising to strengthen Earth’s long-term safety from NEO threats.

Please see attached PDF.

Acknowledgement
Funded by the European Union (ERC, TRACES, 101077758). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council. Neither the European Union nor the granting authority can be held responsible for them.

This LOSSOL presentation will focus on current developments in high energy laser technology, merits and challenges, and Planetary Defense application of Directed Energy Systems for timely intervention of bolides threat to high value assets on the Moon and potential for Earh applications as well.

Keywords: Binary Asteroid Formation, Collisional Spin-Up, N-body simulation
The evolution of rotation rates of small asteroids is subject to mechanisms including: (1) the Yarkovsky-O’Keefe-Radzievskii-Paddack (YORP) effect resulting in a net torque that can secularly modify the body’s rotation rate and orientation; (2) off-spin-axis collisions by projectiles can change the spin state of an asteroid through the imported angular momentum; (3) planetary close encounters which can change the asteroid rotation state due to tidal torques. The relative importance of each mechanism depends on the size, shape, composition, structure, location in the solar system, and encounter geometry.
Some studies [1, 2] show that the YORP effect may gently spin up small asteroids close to and beyond their breakup limit, causing gradual mass shedding from their surface, YORP spin up has been measured over few decades, but the assumption of constant acceleration may not be valid over long time spans, for instance, in the Asteroid Belt, where impacts may change the asteroid local morphology and spin orientation. In the case of the NEA population, a recent study [3] showed that the degraded features on the surface of the primary of the Didymos binary system were more likely produced by impacts than by release of YORP-built surface stress. In fact, Didymos -like many NEAs- has part of its
current orbit inside the inner asteroid belt, where they experienced several tens of DART-like impacts.
As an alternative formation process, a single collision, or a planetary close encounter, may abruptly spin up the body well beyond the breakup limit, causing sudden fission of the body. Such strong impacts may potentially cause sudden spin-up of the parent body above its spin barrier, potentially leading to a binary system.
[4] simulated the main belt asteroid collisional histories, showing that the well-known observed asteroid spin barrier can be reproduced by spin evolution from collisions alone, YORP is not required.
Asteroids with diameters from 1 to around 10 km can be spun up to -and over- the spin limit by a few events, rather than by many small impacts. We study such processes numerically, modelling asteroids as gravitational aggregates with an updated soft-sphere-element-method implementation of the PKDGRAV N-body gravity code [5, 6, 7, 8] for the handling of non-spherical components. We developed a pipeline called SHattering EXperiments to Synthetic Shapes through PhotogrammetrY, (SHEXSSPY), to reproduce realistic angular shapes and the interlocking effect of the aggregate components.
We find that relatively large fragments and clumps may detach from the original body -triggered by impact or close encounter- and potentially evolve into a binary system, asteroid pair, contact binary,
or simply be disrupted, depending on the collision conditions and transference of angular momentum.
A significant part of the internal structure of satellites formed in this way may come from material well beneath the surface of the primary. This is likely different than in the YORP-induced binary formation
mechanism. The upcoming measurements of the internal structure of the Didymos system components by the Hera mission (ESA) may provide insights into formation mechanism of binary asteroids.

body (Selam) of the Dinkinesh binary system.

References

[1] K. J. Walsh, D. C. Richardson, P. Michel, Rotational breakup as the origin of small binary asteroids, Nature 454 (2008)
188–191.
[2] K. J. Walsh, D. C. Richardson, P. Michel, Spin-up of rubble-pile asteroids: Disruption, satellite formation, and equilibrium shapes, Icarus 220 (2012) 514–529.2
[3] A. Campo Bagatin, A. Dell’Oro, L. M. Parro, P. G. Benavidez, S. Jacobson, A. Lucchetti, F. Marzari, P. Michel, M. Pajola, J.-B.
Vincent, Recent collisional history of (65803) Didymos, Nature Communications 15 (2024) 3714.
[4] K. A. Holsapple, Main belt asteroid collision histories: Cratering, ejecta, erosion, catastrophic dispersions, spins, binaries,
tops, and wobblers, Planetary and Space Science 219 (2022) 105529.
[5] D. C. Richardson, T. Quinn, J. Stadel, G. Lake, Direct Large-Scale N-Body Simulations of Planetesimal Dynamics, Icarus 143
(2000) 45–59.
[6] J. G. Stadel, Cosmological N-body simulations and their analysis, Ph.D. thesis, University of Washington, Seattle, 2001.
[7] S. R. Schwartz, D. C. Richardson, P. Michel, An implementation of the soft-sphere discrete element method in a high-
performance parallel gravity tree-code, Granular Matter 14 (2012) 363–380.
[8] J. C. Marohnic, J. V. DeMartini, D. C. Richardson, Y. Zhang, K. J. Walsh, An Efficient Numerical Approach to Modeling the
Effects of Particle Shape on Rubble-pile Dynamics, Planetary Science Journal 4 (2023) 245.

In asteroid kinetic deflection missions, the presence of ejecta leads to a phenomenon where the system's momentum appears to be "amplified" after impact. In our previous work, we leveraged this phenomenon and demonstrated, through simulations of kinetic deflection missions to 32 potentially hazardous asteroids (PHAs), that striking a point offset from the geometric center of the asteroid results in a greater deflection distance compared to collision at the geometric center with an average increase of 81.05$\%$, while keeping all impact conditions unchanged. In the work, the transfer trajectory is adopted using the simplest two-impulse transfer, also referred as Lambert transfer. One of the conclusions indicates that as the interception angle $\alpha$ increases, the advantage of the Best Impact Point (BIP) strategy over the Center of Geometry (COG) strategy becomes more pronounced.

Real space mission involving multi-impulse or continuous thrust transfer trajectories, the cost function is defined as the deflection distance, with the objective of maximizing it. Adoption of the COG strategy usually results in an interception angle $\alpha$ close to zero, aligning the spacecraft velocity vector nearly parallel to the asteroid velocity vector at the moment of impact. However, with the introduction of the BIP strategy, it is not always necessary to have a near-zero interception angle $\alpha$ to maximize the deflection distance. This raises essential questions about the influence on trajectory optimization design. Does incorporating the BIP strategy lead to a notable improvement in deflection distance compared to designs that only consider the COG strategy? These questions drive the deeper investigation presented in this paper.

This study aims to simulate the defense of 24 PHAs using both the BIP and COG strategies. A comparative analysis of the two approaches will be conducted to verify the feasibility of eccentric impact strategies in planetary defense missions. It is predicted that for each simulation of every PHA, there exists a transfer trajectory with a larger interception angle and strike at a best impact point, results in a deflection distance superior to that of the traditional approach with a near-zero interception angle and a strike at the geometric center. point, which results in a deflection distance superior to that of the traditional approach with a near-zero interception angle and a strike at the geometric center.

Multiphysics simulations involve a number of modeling choices, including material strength, meshing strategies, and equation of state. These methods are often verified using ideal scenarios (e.g., uniform mesh, analytic solutions available), but there are scenarios during which this approach is not feasible. Planetary defense, a research subject focused on protecting Earth from impacts from potentially hazardous objects (PHOs), is a matter of both national and global security. Simulations of planetary defense applications involve spatial scales of hundreds of kilometers and temporal scales on the order of seconds or longer. Thus, modeling choices must be made to ensure that knowledge can be obtained in a timely manner, as mission design can take years and flight time from Earth to a PHO can take from 6 months up to years. Understanding how these choices (e.g., a varied mesh resolution that is more resolved around the impact point and less resolved at the edges) contribute to overall uncertainty is of utmost importance in preparation for a variety of potentially catastrophic scenarios. In this work, we examine how specific modeling choices contribute to uncertainties in numerical simulations as a means of better understanding how to best interpret results and apply the appropriate error bars given a time-sensitive scenario, such as an impending meteor strike. We also discuss the simulations run as part of the Near Earth Object Table Top Exercise of 2024, which considered a number of possible mitigation strategies and associated timelines.

Keywords: kinetic impactor, asteroid deflection, asteroid disruption

The potential for accidental disruption of an asteroid during a kinetic impact deflection attempt poses significant risks for planetary defense strategies. As the velocity change applied to an asteroid during a deflection attempt increases, so does the likelihood of inadvertent fragmentation or partial disruption. Understanding the thresholds for safe deflection is crucial, as exceeding these limits can lead to unintended consequences, such as the creation of a cloud of hazardous fragments that may pose a residual threat, one that is potentially equal to or greater than that posed by the original object. Additionally, understanding the requirements for an intentional robust disruption that produces small, well-dispersed fragments opens additional mitigation mission design possibilities.

The characteristics of both the asteroid and the impactor influence the outcome of a kinetic impact. Asteroids exhibit a wide range of sizes, shapes, compositions, and structures, all of which affect an asteroid’s response to an impulsive deflection attempt. Properties like porosity and cohesive strength, for instance, have been shown to significantly affect impact cratering as well as the efficacy of a deflection attempt and fragmentation risk. The mass, velocity, shape, and impact angle of the impactor also affect the response of the asteroid and therefore the final outcome of a mitigation mission.

We use impact simulations in the smoothed-particle hydrodynamics code, Spheral++, to examine the effects of systematically varying a subset of these properties. We particularly focus on 3D simulations of the asteroid in the PDC25 hypothetical threat exercise to examine possible risks associated with an attempted kinetic deflection both with and without reconnaissance. An exemplar simulation output is shown in Figure 1. We compare our simulations to several heuristics for asteroid disruption, including the velocity change as a fraction of escape velocity (e.g., [1]), the specific energy of impact (e.g., [2]), and the specific energy of shattering or disruption (e.g., [3]).

Figure 1: A 2D slice of a 3D simulation of an impact into a monolithic asteroid. This case represents the 50th percentile object, by mass, during Epoch 1 of the PDC25 scenario. The asteroid material is modeled as initially intact rock (light grey), and it fractures and damages (black) beneath the impactor.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-2001329

References:
[1] Miller, P.L. and Dearborn, D.S.P. (2015) Defending Against Asteroids and Comets, Handbook of Cosmic Hazards and Planetary Defense.
doi: 10.1007/978-3-319-02847-7_59-2
[2] Sanchez, J.P., Vasile, M., and Radice, G. (2010) Consequences of Asteroid Fragmentation During Impact Hazard Mitigation, Journal of Guidance, Control, and Dynamics, v. 33, p. 126-146.
doi: 10.2514/1.43868
[3] Holsapple, K.A., and Housen, K.R. (2019) The catastrophic disruptions of asteroids: History, features, new constraints and interpretations, Planetary and Space Science, v. 179, 104724.
doi: 10.1016/j.pss.2019.104724

(See attached file for formatted layout and figures.)

We developed asteroid rubble pile simulations made of crushed basalt. Within the DART community, nearly all computations were performed with basalt as a surrogate for the Dimorphos surface material since it is viewed by many as an appropriate analog to the asteroid material. Basalt was also used by DART Investigation Team members and others in impact computations. Some of our basalt targets had the crushed basalt held in place with a binder (grout with water). Some targets did not – the crushed basalt material was packed into the box. Either a binder or packing was required since our targets hang vertically in a ballistic pendulum. The targets are large – their size is on the order of 60 x 60 x 30 cm and they exceed 200 kg in mass. Using our large 38-mm two-stage light gas gun (for the 5.35 km/s shots) and a 50-mm powder gun (for the 2 km/s shots), we launched aluminum spheres of diameters 2, 3 and 4.45 cm (Table 1).

TABLE 1. Nominal experimental impact conditions for the aluminum sphere impactor.

Projectile diameter (cm) Projectile mass (g) Impact speed (km/s) Momentum (kg m/s) Energy (kJ)
2.0 11.4 5.35 69 163
3.0 38.2 2.05 78 80
3.0 38.2 5.35 204 547
4.45 128 2.05 262 269

A total of 17 new shots into crushed basalt were performed [1]. These add to impacts performed prior to the DART spacecraft impact into Dimorphos, where our group performed impact tests into rock structures measuring momentum enhancement [2,3]. One of these earlier targets was a collection of rocks held in place by cement [2]. In particular, the measured  in that test was 3.4 for an impact of a 3-cm-diameter aluminum sphere at 5.44 km/s. The crushed basalt targets had β ranging from 2.12 to 2.83 for the 5.5 km/s shots and 1.52 to 2.51 for the 2 km/s shots. Thus, these crushed basalt shots showed a lower momentum enhancement than some of our previous rock impact work where the rock was more consolidated.
Material properties were measured for the crushed basalt targets such as compressive strength of the material. The strength showed a final-target-density dependence. Work is ongoing in modeling the impacts and comparing to the experimental impact momentum enhancement β as well comparing to the DART mission result.
These experiments should play an important role in the momentum enhancement studies in general and in the DART results analysis in particular by pinning down some specific  data points with a well characterized experiment at impact speeds of interest for the DART program with targets made of distributed rocks. We will present some of our related computations.

Figure 1. Impacts at 2 km/s by a 4.45 cm diameter sphere of aluminum. Left: A post-test crushed-basalt target hanging in the pendulum (Test 7). Right: roughly 8 milliseconds after impact (projectile came from right to left; Test 1).
1. “Momentum enhancement from impacts into crushed basalt at 2 and 5.5 km/s, motivated by DART,” J. D. Walker, S. Chocron, D. J. Grosch, D. D. Durda, S. Marchi, M. V. Grimm, C. Sorini, Proceedings of the 2024 Hypervelocity Impact Symposium, September 9-13, 2024, Tsukuba, Japan.
2. “Momentum enhancement from a 3 cm diameter aluminum sphere striking a small boulder assembly at 5.4 km s−1,” J. D. Walker, S. Chocron, D. J. Grosch, S. Marchi, A. M. Alexander, Planetary Science Journal 3 215, 2022. https://doi.org/10.3847/PSJ/ac854f.
3. “Momentum enhancement from 3-cm-diameter aluminum sphere impacts into iron and rock at 5 km/s,” J. D. Walker, S. Chocron, D. J. Grosch, S. Marchi, A. M. Alexander, Int. J. Impact Engng 180, 104694:1–11, 2023.

After the success of the NASA/DART mission (Daly et al., 2023; Chabot et al., 2024), attention has turned to demonstrating alternative technologies for mitigation and deflection. The gravity tractor is one such technology that uses its own gravity to slowly ``tow'' an asteroid and alter its trajectory (Lu and Love, 2005). Using the Gauss planetary equations, we derive a simple first-order metric to determine the effectiveness of a gravity tractor for a given asteroid. This metric estimates how quickly a gravity tractor changes the orbital period of a body. The metric can be applied to both heliocentric orbits on single asteroids and to a secondary body's orbit around a primary in a binary asteroid system. By comparing the metric for heliocentric orbits versus those for binary systems, we find that binary systems are better suited for demonstration missions than single objects. The metric can also be used to compare two separate systems and determine which one is more suitable for a gravity tractor demonstration mission. The metric may also be generalized to compare kinetic impactors to gravity tractors in the future.

The metric is
\begin{equation}
\mathcal{C} = \frac{a^2}{\sqrt{1-e^2}}\frac{M_3}{M_1 + M_2} \frac{1}{r_{2/3}^2}
\end{equation}
where $a$ and $e$ are the object's semi-major axis and eccentricity, respectively. $M_3$ is the mass of the gravity tractor while $M_1$ is the mass of the center body and $M_2$ is the mass of the body being perturbed. $r_{2/3}$ is the distance from the center of the gravity tractor to the center of mass of the perturbed body. As it is written, $\dot{P} \propto \mathcal{C}$ (i.e., the rate of change to the period of the perturbed body is proportional to the metric, $\mathcal{C}$). For a single body on a heliocentric orbit, we can define
\begin{equation}
\mathcal{C_\odot} = \frac{a_\odot^2}{\sqrt{1-e_\odot^2}}\frac{M_3}{M_\odot + M_2} \frac{1}{r_{2/3}^2}
\end{equation}
which is identical to the previous metric but with the solar mass, $M_\odot$, heliocentric semi-major axis, $a_\odot$, and heliocentric eccentricity, $e_\odot$, substituted in. For cases where we may directly compare a binary system to a heliocentric orbit, we find that $\mathcal{C} > \mathcal{C}_\odot$. For example, $\mathcal{C}/\mathcal{C}_\odot \approx 76$ for Dimorphos using the most up-to-date values of the Didymos-Dimorphos system (Chabot et al., 2024).

As the threat of hazardous Near-Earth Objects (NEOs) continues to pose a potential risk to Earth’s safety, developing effective planetary defense strategies is becoming an urgent priority. One promising approach is the use of a nuclear deflection mission, leveraging the energy released by a nuclear device to alter the trajectory of an incoming NEO. This abstract outlines the key technologies and mission capabilities required for successfully deploying a nuclear deflection strategy to mitigate the impact risk from a hazardous NEO.

Key technologies are needed in areas such as precision targeting, nuclear device deployment, radar fuzing, and post-impact trajectory prediction. This includes the development of autonomous spacecraft capable of rendezvousing with the NEO in a timely manner, deploying a nuclear device with high accuracy, and assessing the effectiveness of the deflection through advanced sensors and real-time data analysis. Additionally, nuclear safety protocols, including radiation shielding and environmental monitoring, must be incorporated into the mission design to ensure that the operation does not produce unintended consequences for Earth's environment or orbit.

This study discusses the scientific and engineering challenges of safely and effectively delivering a nuclear device to an NEO and the integration of international collaboration in the development and deployment of planetary defense technologies. By outlining these critical technological needs, this work aims to provide a foundation for future mission planning and contribute to the global effort to safeguard Earth from potential NEO hazards.

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525.

The planetary defense community practices mission-planning to deflect or disrupt any near earth asteroids (NEAs) that are found to be on an Earth-impacting trajectory. Many scenarios must be con- sidered to determine the optimal mission type to recommend. While a kinetic impactor is the first choice for a deflection mission, either a large asteroid or a short warning time may require using a stand-off nuclear explosive device (NED) to deflect the NEA. Therefore a simple analytic model to estimate the $\Delta v$ imparted to a NEA by a stand-off NED is a valuable tool for mission planners. Roughly a decade ago an initial analytic model was provided to NASA for this purpose. In 2021 the model was somewhat revised and published[1]. In 2023 a further revision[2, 3] was presented to better handle cases that had high x-ray fluences.
The revised model is still in need of improvement. The model was fit to calculations for SiO$_2$ at full density, 2.65 g/cm$^3$. Since NEAs are rarely at full density[4, 5, 6, 7] the effect of porosity is currently handled by using the density scaling inherent in the model. Since the density-scaled analytic model diverges from simulations that include porosity the current results are likely inadequate and should explicitly include simulated porosity data to fit the model. The model would also benefit from having coefficients for materials other than SiO$_2$.
We have performed asteroid deflection simulations with four materials (SiO$_2$, forsterite, ice, and iron), four porosities (10%, 30%, 50%, and 70%), two diameters (100 and 500 m), several heights of burst (HOB), and several fluences. These hydrocode simulations are initiated using Burkey’s energy deposition model[8]. The goal is to provide model coefficients for each material. Whether the coefficients need to include a dependency on porosity will be investigated as well. The uncertainty of the coefficients and the $\Delta v$ provided by the model will be examined and presented as results warrant.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

References
[1] R. A. Managan, J. V. Wasem, K. M. Howley, Near Earth Object Deflection Formulae, in: Proceedings of the 7th Planetary Defense Conference, LLNL-PROC-821571, IAA. April 26–30, 2021. IAA-PDC21-0X-YY.
[2] Extending NEO Deflection Formulae to High Fluences, LLNL-PROC-821571, Seventh IAA Planetary Defense Conference, IAA, 2023.
[3] R. A. Managan, M. T. Burkey, Analytic Deflection of Asteroids by NEDs, https://github.com/LLNL/Analytic Deflection of Asteroids by NEDs., 2023.
[4] Hanus, J., Viikinkoski, M., Marchis, F., Durech, J., Kaasalainen, M., Delbo, M., Herald, D., Frappa, E., Hayamizu, T., Kerr, S., Preston, S., Timerson, B., Dunham, D., Talbot, J., Volumes and bulk densities of forty asteroids from adam shape modeling, A&A 601 (2017) A114.
[5] D. Scheeres, J. McMahon, A. French, D. Brack, S. Chesley, D. Farnocchia, Y. Takahashi, J. Leonard, J. Geeraert, B. Page, et al., The dynamic geophysical environment of (101955) Bennu based on {Osiris-Rex} measurements, Nature Astronomy 3 (2019) 352–361.
[6] M. Kanamaru, S. Sasaki, M. Wieczorek, Density distribution of asteroid 25143 itokawa based on smooth terrain shape, Planetary and Space Science 174 (2019) 32–42.
[7] S. Watanabe, et al., Hayabusa2 arrives at the carbonaceous asteroid 162173 ryugu—a spinning top–shaped rubble pile, Science 364 (2019) 268–272.
[8] M. T. Burkey, R. A. Managan, N. A. Gentile, M. B. Syal, K. M. Howley, J. V. Wasem, X-ray energy deposition model for simulating asteroid response to a nuclear planetary defense mitigation mission, The Planetary Science Journal 4 (2023) 243.

LLNL-ABS-2001221

The physical and chemical composition of asteroids plays a pivotal role in determining the efficacy of planetary defense strategies. Asteroids are classified into three primary types: metallic (M-type), carbonaceous (C-type), and stony (S-type). Each composition presents unique challenges and opportunities for mitigation techniques, such as kinetic impactors, nuclear disruption, and gravity tractors.
Carbonaceous asteroids, rich in water and organic materials, often exhibit lower densities and cohesive strengths, making them susceptible to fragmentation under high-energy impacts. However, their porosity complicates the efficient transfer of momentum during kinetic deflection efforts. Stony asteroids, comprising silicate minerals and rock, are more rigid but can fracture unevenly, posing risks of creating unpredictable secondary fragments. Metallic asteroids, primarily composed of iron and nickel, are structurally robust and highly reflective. Their composition enhances the potential for gravity tractor applications but presents significant challenges for kinetic or explosive deflection due to their density and rigidity.
Recent advancements in spectral analysis and radar imaging have enhanced our ability to determine asteroid compositions remotely, offering critical insights for designing mitigation strategies. Space-based telescopes, such as NEOWISE, have contributed significantly to the classification of Near-Earth Objects (NEOs) by detecting unique thermal and albedo signatures. These data inform mission planning, allowing engineers to tailor deflection techniques to the asteroid’s material properties. This review also examines the implications of asteroid spin rates, shape irregularities, and internal structure on mitigation strategies. For instance, a high spin rate in a metallic asteroid might render kinetic impactors less effective, necessitating the use of a gravity tractor or a multi-stage deflection approach. Moreover, understanding asteroid composition is critical for minimizing unintended consequences, such as fragment dispersion during nuclear disruption or impact-generated debris. The presentation will highlight a matrix of mitigation techniques optimized for different asteroid types, combining experimental results from missions like DART and theoretical models. Visual aids will include asteroid composition maps, deflection strategy simulations, and case studies from past and ongoing planetary defense missions.

Keywords: Asteroid Deflection, Asteroid Disruption, Nuclear Mitigation Strategy, Asteroid Composition, Near-Earth Object

Session: Deflection/Disruption Modeling and Testing

Space is perpetually monitored by scientists for near-Earth objects (NEOs) that could potentially collide with Earth. If a problematic NEO is detected early enough, then multiple mitigation options can be devised. One mitigation option is to detonate a nuclear explosive device (NED) a short distance from the NEO so the surface material vaporizes and is blown off by the deposited X-rays, which imparts a shift in momentum, redirecting the NEO away from Earth. This process involves some of the X-rays being deposited into the NEO while the rest are reradiated away at the surface. The interplay between these two processes is critical for calculating the effectiveness of this mitigation option. The success of asteroid disruption and deflection is correlated with blowoff momentum, which can be used to calculate the NEO’s deflection velocity.
The momentum of blown-off surface material is highly dependent on the composition of the asteroid. Previous work by Burkey et al. (2023) simulated the first few microseconds of NED detonations near asteroids in Kull (a radiation-transport hydrodynamics code created for inertial confinement fusion) using simple, asteroid-like materials: SiO2, Forsterite (Mg2SiO4), Iron, or Ice. Because NEDs cannot be tested in space, this work must be done through simulations. Incorporating realistic and complex material compositions such as CI Chondrite-type asteroids increases the accuracy of these simulations.
Preliminary calculations, shown in Fig. 1, indicate that changing the simulated opacity to better reflect complex, asteroid-like compositions leads to significant differences in the magnitude of blowoff momentum. 

Fig. 1: Percent difference in blowoff momentum as a function of fluence when the opacity of the asteroid is changed from the opacity of the original material to the opacity of CI Chondrite for materials: SiO2 (purple), Forsterite (green), Ice (blue).

We present a study demonstrating how changing the varied material composition of realistic asteroids affects the blowoff momentum using similar simulations to those in Burkey et al.
Prepared by LLNL under Contract DE-AC52-07NA27344.
LLNL-ABS- 2001302

Near-earth objects can range from less than one meter to tens of kilometres. While smaller NEOs explode entering the atmosphere, those bigger than 140 m are considered potential hazardous objects (PHO) and are monitored to avoid future catastrophes. Even though early detection and warning systems help us in analysing the threat, we need technology to deflect or destroy the PHOs before they reach near Earth. This research explores the current state of research and development in NEO mitigation technologies, which include kinetic impactors, gravity tractors, and nuclear detonation, with their limitations and advancements.
We categorise our research into two major options available: deflection of asteroids or exploding the asteroid. To study deflection, we examined many approaches, including using steam generated by charged particles to apply force on the asteroid, altering its course, utilising the Lorentz force theory to interact with asteroid plasma via a magnetic field, or using the laser ablation method, where we use high-energy lasers on the asteroid surface to vaporise the material to create thrust and deflect it. We also examined the DART mission concept, gravity tractor, and upgraded gravity tractor to get a deeper understanding of the mechanisms for asteroid deflection.
While deflections seem promising, they don’t provide viable solutions for terminal scenarios, like little warning time before the impact of the Chelyabinsk. For these kinds of asteroids, we need better mechanics to destroy them before they impact the Earth. For exploding the asteroid, we studied methods like kinetic impactors, which are primarily used for deflection but if targeted for smaller asteroids, the impact can destroy the asteroid. We also included nuclear detonation methods to destroy the asteroids. With the advancement in risk assessment, we must consider the potential risk involved in destroying an asteroid in space or the Earth's atmosphere. We also consider the fragmentation risk of destroying an asteroid as it can create debris and the use of nuclear weapons in space while considering the current technological limitations as well. With this comparative study, we have included suggestions to analyse risk and take necessary majors by global collaboration.

In this paper, I argue for a new perspective on the design of nuclear weapons for planetary defense missions. At the time of writing, the mandate for Sandia’s planetary defense team is to modify existing stockpile weapons as needed for employment in the deflection of a near-earth object. However, this runs up against a universally acknowledged but seldom-mentioned problem: the placement of nuclear weapons in space is explicitly banned under international law. For this reason, I urge the consideration of non-traditional nuclear explosive designs in addition to our current work scope. We ought to design a nuclear explosive device that, if used in a wartime, re-entry setting, would fail by design. This could be done by removing the ablative heat shield, or by changing the overall geometry of the device to be something that would exhibit abysmal performance on re-entry. When we take this idea seriously, it also opens up the design space.

The only use case for such a nuclear explosive device would take place well beyond the lunar orbit. This way, any gamma ray flux produced by the nuclear explosive would diminish as 1/r^2 and would not pose a threat to Earth-orbiting satellites. Any nuclear detonation within the lunar orbit is not likely to produce the deflection required of a planetary defense mission, rendering such a scenario moot.

I offer a nominal trade study on how this freer design space can be used to improve the radar performance and fuzing of such a device. We are no longer concerned with a whole host of problems that are specific to re-entry environments. We should take the freedom afforded by this change of environment and use it to tailor a device that only has one job: to target and deflect near-earth objects.

SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525

In the event of a potential asteroid impact on Earth, if an attempt can be made to prevent it, time will be of the essence. Simple models for determining what mission types are best-suited to deploy based on the circumstances are invaluable tools for facilitating a swift response. When NASA mission designers are exploring the mission space and uncertainties for exercises, such as the one aligned with this conference, they often rely on one such analytic model that estimates the deflection velocity (ΔV) a nuclear explosive device (NED) can impart to an asteroid.

The original analytic model delivered to NASA about a decade ago by LLNL researchers was based on 16 simulations covering various NED yields and heights of burst (HOBs) [1]. This model has since been updated with more simulations and higher fluence ranges [2,3] using new modeling capabilities [4] and the mesh-based code ARES. Development of an even more thorough update is underway, incorporating additional material options and properties, fitted with a larger set of simulation data. However, all these analytic fits are informed by deflection scenarios, with little chance of accidental disruption.

Mission designers often use this analytic model alongside generally accepted “rules-of-thumb” that compare the mission-imparted ΔV against the asteroid’s escape velocity (Vesc) to assess the feasibility of accidental weak disruption (0.1Vesc)[5] or intentional robust disruption (10Vesc). The physics involved during a disruption includes shockwave propagation and the material’s strength and damage. In contrast, the deflection simulations are primarily influenced by the vaporization of surface material due to the NED’s x-ray photons, with minimal contribution from a shockwave. Therefore, the analytic model is ill-suited for informing disruption scenarios, especially robust or intentional ones.

Though disruption scenarios are best simulated using a high-fidelity, multi-physics code that is well benchmarked to experimental strength and damage (such as Spheral), the authors recognize that these simulations are costly in terms of time and computing resources with current capabilities. Therefore, alongside the updated analytic model, we present results from a suite of simulations in ARES (such as in the attached figure) to better inform mission designers about the likelihood and nature of disruption for various scenarios to discourage over-extrapolation of the analytic model.

Prepared by LLNL under Contract DE-AC52-07NA27344. LLNL-ABS-871403.

The threat of asteroid impacts on Earth has driven the development of advanced deflection technologies, forming a cornerstone of planetary defense strategies. This paper reviews the latest advancements and challenges in asteroid deflection technologies, focusing on kinetic impactors, gravity tractors, nuclear explosive devices, and hybrid methods. Each technology is evaluated for its feasibility, mission readiness, and effectiveness under various asteroid compositions and trajectories. The study incorporates insights from recent missions such as NASA’s DART, which demonstrated the viability of kinetic impactors, alongside theoretical analyses and optimization models for deflection strategies. It also talks about emerging concepts like laser ablation and electrostatic repulsion, which emphasizes their potential for addressing complex scenarios such as binary asteroid systems or high-velocity impacts. Special attention is given to the influence of asteroid properties—density, porosity, rotation, and surface cohesion—on the efficacy of deflection techniques.
Furthermore, the paper highlights the role of advanced mission design tools in optimizing deflection campaigns. These tools enable rapid trajectory calculations and trade-off analyses, facilitating the selection of optimal spacecraft configurations and deflection windows. Challenges such as system integration, cost constraints are also discussed. Current research were synthesized and gaps in existing knowledge were identified. This study provides a comprehensive framework for advancing asteroid deflection technologies and aims to guide future developments in planetary defense, ensuring preparedness for potential asteroid threats and safeguarding Earth from catastrophic impacts.

Keywords: Catastrophic Disruption, Kinetic Impactor, Laboratory Experiments, Numerical Simulations

NASA’s DART mission successfully altered the orbit of a 160-m-diameter asteroid, demonstrating kinetic impactor technology for Planetary Defense. While successful, the DART mission also raised new questions about the extent at which kinetic impactors could be used in real scenarios. In particular, kinetic impacts on 50- 100 m-diameter NEAs could lead to a disruption event, rather than a deflection. In such an event, it is not yet clear that the threat would be adequately mitigated, or if the threat would be exacerbated by multiplying the number of potential Earth-bound impactors. Recent research into this problem has used crude approximations for the disruption limits of asteroids in this size range to argue against the use of kinetic impactors, favoring alternative mitigation techniques. Here, we study the outcomes of impacts in the catastrophic disruption regime of small coherent asteroids to better understand the limits at which kinetic impactors could be used for asteroid mitigation.
The goals of this work are to:
1. Conduct hypervelocity impact experiments and simulations on to asteroid simulant to better understand the disruption threshold of coherent NEAs.
2. Conduct numerical simulations of disruption dynamics to evaluate the extent to which catastrophic disruption mitigates or exacerbates the asteroid threat.
To achieve the first goal, we are conducting hypervelocity impact experiments using the HyFire lab at the Hopkins Extreme Materials Institute. This includes a two-stage gas gun and a suite of diagnostic tools which include highspeed cameras capable of capturing the post-impact dynamics of fragments as a target is disrupted. We will be using asteroid analogs in our experiments as these would be the best analogs to NEAs. The experiments inform larger-scale simulations of disruptive impacts on to 50-100 m-diameter targets by a kinetic impactor.
To achieve the second goal, we use the results of our experiments and simulations to setup computational simulations of the dynamics of impact fragments following a kinetic impact, using the N-body code pkdgrav. For this work, we will simulate the disruption of hypothetical 2024 PDC25 for cases of its most likely size range (90 - 160 m). Using our high-fidelity disruption modeling, we will present an assessment of the consequence of the disruption of 2024 PDC25 at different points in time before its potential impact date of April 24, 2041.

The PI method represents an alternative approach to planetary defense from asteroids which utilizes energy transfer to disrupt an asteroid rather than momentum transfer to alter its orbit. The method makes use of various possible configurations of hypervelocity penetrators which can operate in one of six modes, ranging from asymmetrical fragmentation for enhanced deflection (which is useful for longer warning time scenarios) to complete disruption and permanent removal of the threat (which is useful for terminal interdiction scenarios with short warning times). While diverse in their outcomes, all six modes of operation involve the hypervelocity impact of high density kinetic penetrators. At speeds of impact $<10$ km/s, the passive penetrators can be used to clear the way through the target for explosive charges (conventional or nuclear) to be delivered below the surface, which is also useful for large targets ($\sim1$ km diameter). At speeds $>10$ km/s, the penetrators carry enough kinetic energy to vaporize a significant volume of asteroid material local to the impact site and robustly disrupt the target themselves without the use of conventional explosives or a nuclear explosive device (NED) for targets in the 20 -- 500 m diameter range. We will present the results of an ongoing simulation campaign dedicated to investigating the hypervelocity impacts using the Lawrence Livermore National Laboratory (LLNL) arbitrary Lagrangian-Eulerian (ALE) hydrodynamics code ALE3D run with the High-End Computing Capability (HECC) at NASA Ames Research Center.

Using ALE3D, we model hypervelocity impact dynamics in 2D and 3D using equation-of-state material models which include shock response and material vaporization/ionization. We make use of the Livermore Equation of State (LEOS) tables as the building blocks of our material models. In previous work \cite{Lubin1,LubinCohen1}, we investigated hypervelocity impact events with asteroid targets in the 20 – 100 m diameter range and concluded that robust disruption could be achieved via 20 km/s impacts with 100 and 500 kg 10:1 aspect ratio cylindrical tungsten penetrators. Such modest penetrator mass enables a ``single launcher solution" for threats in this diameter range with vehicles such as the SpaceX Falcon 9 (which has a payload capacity of $\sim2500$ kg with $C_3>0$), or similar. For this work, we extend this range up to 1 km diameter targets, and we couple hypervelocity impact simulations with energy injection simulations to model the delivery of explosive charges, both conventional and nuclear, to significant depths beneath the surface before detonation. We will show through ALE3D simulation results how this method is effective in mitigating asteroids in the 100 m -- 1 km diameter range in a number of interdiction modes, from terminal modes which completely disrupt the threat into small fragments, to long warning time modes which utilize asymmetrical fragmentation for enhanced deflection.

Keywords: Rapid Response, Reconnaissance Spacecraft, Mitigation Spacecraft, Short-Warning Time

The Planetary Defense Community has worked tirelessly over the last 30 years to detect and catalog potential asteroid and comet impact threats to the Earth. Great progress has been made in our knowledge of the compositions and orbits of the millions of asteroids and comets in the solar system. Because of this effort, we should have many years, perhaps even decades, of warning prior to a major impact threat.

Unfortunately, it is still possible that comets or smaller, darker asteroids, approaching from the direction of the Sun or from the outer solar system, could pose a threat with much shorter warning time. It is imperative that we prepare now to respond to such threats as rapidly as possible. Typical timelines for the design, construction, test, and launch of research spacecraft are on the order of four years or more once the team has Authorization to Proceed (AtP). AtP often follows several years or even decades of preliminary design work and scientific justification leading up to initial mission proposal and Phase A design studies. For maximum probability of mission success, established procedures for design, build, test, and launch of Planetary Defense missions should be followed whenever possible. We suggest it is possible to cut at least three years from our response time following AtP while maintaining high reliability for both reconnaissance and mitigation spacecraft.

We propose building and warehousing a pair of flexible reconnaissance spacecraft and a pair of flexible mitigation spacecraft. (Redundancy is important to mitigate potential launch failures.) If a threat arises, either set of spacecraft could be rapidly launched after readiness testing, transport to launch site, and integration onto an available launch vehicle. The individual spacecraft would be the result of meticulous design, careful construction, and thorough testing both before storage and prior to launch. Defense of our planet would not be a last-minute panicked response to an imminent impactor, but a carefully considered, planned series of missions to characterize the threat and, if necessary, mitigate potential disaster with readily available resources.

In this paper, we describe our proposed program for providing stored rapid response Planetary Defense spacecraft. The production of replacement spacecraft would be a continuous process where, after 10 – 15 years in storage, the stored spacecraft would be replaced with more modern versions (at affordable cost, in consequence of judiciously re-using design elements). The previously stored spacecraft would be released to the scientific community for a new mission proposed through an open AO (Announcement of Opportunity). This program would ensure that the world would always have a readily available and reasonably up to date set of reconnaissance and mitigation spacecraft to respond to any potential Earth impact threat. It would also provide a steady supply of spacecraft for gathering competitively proposed scientific data at a regular cadence. The very large population of asteroids ensures that many interesting and worthwhile destinations will always be available for the spacecraft, and many in situ measurements of asteroids is essential for improving both our Planetary Defense capabilities and scientific understanding.

Keywords: asteroid flyby, asteroid reconnaissance, mass estimation, mass uncertainty

The near-Earth object (NEO) discovery rate has increased in recent years, and the discovery rate is expected to further increase dramatically when new telescope systems such as LSST and NEO Surveyor come online during the next several years. Significant increases in NEO discovery rate makes it more and more likely that an asteroid on an Earth-impacting orbit will be discovered during the next decade. Accurately estimating the mass of Earth impacting asteroids is essential for predicting potential Earth impact effects and designing spacecraft missions to prevent Earth impacts. However, asteroid mass estimates are often clouded with significant uncertainties if the asteroid is only observed by ground-based telescopes. The quickest way to reduce these uncertainties is to send a fast flyby
spacecraft mission to reconnoiter the asteroid. Directly measuring asteroid mass with a fast flyby mission is very difficult, but capturing camera images of the asteroid is relatively straightforward. Spacecraft
camera images of the asteroid can be used to build a shape model of the asteroid using techniques such as stereophotoclinometry, and that shape model yields an estimate of the asteroid’s volume and associated uncertainty. However, without additional measurements or a priori constraints, significant uncertainties remain in the asteroid’s base material density and bulk porosity (or, taken together, bulk density).

Asteroid mass can be described as the product function ( f ) of volume, base material density, and bulk porosity, and an expression can be derived relating percent uncertainty in f to the uncertainty in f ’s dependent variables. Asteroid volume uncertainty can be significantly reduced by an appropriately designed flyby mission [1]. Table 1 lists previous missions where spacecraft flyby improved knowledge of the visited asteroids. This begs the question ”Given a particular volume uncertainty from processing spacecraft camera images of an asteroid, what are the required a priori uncertainties in bulk porosity and
base material density to keep the resulting mass uncertainty below a particular level?”.

In this study, we explore the interconnected nature of these uncertainties and estimate the lowest asteroid mass uncertainties achievable when only volume measurements are available, based on current abilities to constrain asteroid density and porosity. We also discuss how low the uncertainties on asteroid density and porosity would need to be in order to achieve given levels of asteroid mass uncertainty utilizing only camera imagery collected by fast flyby reconnaissance missions.

The equations and relationships that will be presented can be used to inform asteroid flyby reconnaissance mission design and instrument selection, as they give an indication of the instrument precision and resolution required to achieve a desired goal in asteroid mass uncertainty. Mission implications from a space-systems perspective are explored, helping to inform mission requirements and performance expectations for a given set of estimated asteroid parameters.

References
[1] [2] [3] P. C. Thomas et al., “Eros: Shape, topography, and slope processes,” Icarus, vol. 155, pp. 18–37, Jan. 2002.
J. Veverka et al., “NEAR encounter with asteroid 253 mathilde: Overview,” Icarus, vol. 140, pp. 3–16, Jul. 1999.
D. K. Yeomans et al., “Radio science results during the NEAR-shoemaker spacecraft rendezvous with eros,” Science, vol. 289,
pp. 2085–2088, Sept. 2000.
[4] J. Veverka et al., “Imaging of Asteroid 433 Eros During NEAR’s Flyby Reconnaissance,” Science, vol. 285, pp. 562–4, Aug.
1999.
[5] L. Jorda et al., “Asteroid (2867) Steins: Shape, topography and global physical properties from OSIRIS observations,” Icarus,
vol. 221, pp. 1089–1100, Nov. 2012.
[6] [7] M.F. A’Hearn et al., “EPOXI at Comet Hartley 2,” Science, vol. 332, pp. 1396–1400, Jun. 2011.
P.C. Thomas et al., “Shape, density, and geology of the nucleus of Comet 103P/Hartley 2,” Icarus, vol. 222, pp. 550–558, Feb.
2013.
[8] J. T. Keane et al., “The Geophysical Environment of (486958) Arrokoth—A Small Kuiper Belt Object Explored by New Hori-
zons,” Journal of Geophysical Research: Planets, vol. 127, May 2022.

Asteroid spacecraft have significant potential in the field of planetary defense, particularly in preventing or mitigating the threat posed by near-Earth objects (NEOs). These objects, which include asteroids and comets, are classified as potentially hazardous if their orbits bring them into close proximity with Earth. While the likelihood of a catastrophic impact is low, the consequences of such an event would be devastating, making planetary defense a high-priority area of research. In early 2025, AstroForge will launch its second mission, Odin, that can act as a future prototype for a rapid response spacecraft for future asteroid deflection, reconnaissance, and landing opportunities. One of the most fundamental roles of asteroid spacecraft in planetary defense is improving the detection and tracking of NEOs. Space missions equipped with advanced sensors and imaging systems can help identify asteroids early in their trajectories, especially those that are smaller or more difficult to spot using Earth-based telescopes. By launching dedicated spacecraft designed to detect and track asteroids, scientists can gather detailed information about their size, composition, orbit, and velocity. This data is crucial for assessing whether an asteroid poses a collision risk with Earth. An AstroForge spacecraft can act as a kinetic impactor, gravity tractor, or a nuclear deflector (as a carrier). Our Odin spacecraft, acting as a potential future prototype Asteroid offers a range of innovative strategies for planetary defense. By improving early detection, monitoring, and providing direct means of impact mitigation, we can play a crucial role in safeguarding Earth from asteroid threats. As technology advances and our understanding of NEOs deepens, asteroid spacecraft will continue to be a critical tool in protecting our planet from potential disasters that could otherwise go undetected or be too costly to prevent using traditional methods. Finally, our follow-on Missions 3 and 4, which both involve landing our future spacecraft on a metallic asteroid body, can provide multiple detection and deflection opportunities as well as in-situ study and sample return, as is the purpose of Missions 3 and 4, respectively.

On September 26, 2022, the DART spacecraft collided with the 160-meter asteroid Dimorphos and shifted its orbital period relative to its 700-meter companion asteroid Didymos by approximately 33 minutes. The Double Asteroid Redirection Test (DART) successfully demonstrated deflection of an asteroid by a high-speed kinetic impactor and enabled in-depth analysis of the experimental results.
The Didymos-Dimorphos binary system was chosen as a test site for this demonstration because the change in Dimorphos' orbital period is directly measurable from the Earth, thus providing an immediate and precise indication of the test outcome. DART’s success suggests that, given sufficient time before impact, an Earthbound asteroid could be deflected away from the threatening trajectory.
This study considers new experimental mission scenarios that reuse Dimorphos as a testing environment for evaluation of additional asteroid deflection technologies and operationalization of abstract concepts into measurable capabilities. As the Didymos-Dimorphos binary system poses no threat to the Earth, further tests would incur no new risks. Experience gained from DART also provides ample context about the specific binary asteroid system as a testing environment.
The 2022 test revealed previously unknown details about the material composition of Dimorphos. This foundation can inform future tests, preempting the need to identify and evaluate a new experimental environment. Improved characterization of Dimorphos by the upcoming HERA mission can also further refine testing parameters for new methods of asteroid deflection. Thus, new tests conducted on this binary system can provide valuable information on the science and technology of asteroid characterization and planetary defense.
Furthermore, future deflection technologies, such as the ion beam shepherd and the centrifugal mass driver, may provide additional benefits if tested in an international collaborative format. Cooperation and transparency can help identify and resolve the wide array of political, legal, programmatic, and operational issues that would arise in any actual campaign to prevent a NEO impact scenario.
Reusing the Didymos-Dimorphos test site can build upon the foundation of previous test missions, validate assumptions and models, demonstrate new asteroid deflection technologies, and expand the planetary defense toolbox that can be applied with confidence at the time of need.

The Pulsar kinetic Impact technology would allow humanity to literally sleep through the threat of a comet or asteroid which posed a threat to Earth. The Pulsar motor is designed to harness nuclear plasma technologies through a direct fusion drive.
Specifications Below:
The Direct Fusion Drive is a revolutionary steady-state fusion propulsion concept, based on a compact fusion reactor. It will provide power of the order of units of MW, providing both thrust of the order of 10−101N with specific impulses between 10,000 – 15,000 seconds and auxiliary power to the space system.
This should be the highest priority for the “Planetary Defense Community” as the Pulsar Motor when connected to a Kinetic Impactor would literally yield and I don’t mean 1 or 2 but possibly 10’s of gigaton’s equivalent power on impact. Far more than enough to ensure that with just 1 or 2 solid Kinetic Impacts an asteroid would be deflected no matter what the size of the Asteroid would be nor its makeup. And with far greater power than any man-made nuclear weapon.
I am asking anybody who is reading this abstract to make this your “Planetary Defense Priority” to see that the Pulsar Motor used to create the greatest “Planetary Defense” Kinetic Impactor in mankind's history. The time is now we have the ability to save ourselves we must do so we have no other choice. With “Global Warming” and so many other threats the imminent threat from an asteroid could be the final blow that tips the “Earth” on its head. Let's Stand together now and realize the chance we have. Look at the ‘DART’ Mission just a small spacecraft that had such a huge effect and was only traveling around 14,760 MPH can you imagine if we had hit at 500,000 MPH that’s around 33.87 times that which we hit Dimorphos. Dimorphos would have been sent permanently out to space and would no longer orbit Didymos. Over the last decade, we have seen that both NASA and the ESA each year attend the Planetary Defense Conferences. And each time admit that there is very little they could do to mitigate the impact of an Asteroid. At the IAA Planetary Defense Conference in 2021 in Vienna Austria NASA ran a real-time simulation of a scenario where an Asteroid had been detected on a path to impact the “Earth”. The study showed once again that ultimately no deflection mission could be launched and the only action that could be taken to save humanity was mass evacuations. That’s why I am asking you the reader to take notice of this groundbreaking new technology called the “PULSAR”. With the “PULSAR” motor attached to a Kinetic Impactor, the result of using it to hit an oncoming Asteroid would be what would be called “A Successful Mitigation and Deflection”.

The European Space Agency (ESA)’s Lunar Meteoroid Impact Observer (LUMIO) mission represents a cutting-edge advancement in understanding the meteoroid environment around the Earth-Moon system. Lead by Politecnico di Milano (PoliMi) and supported by the Italian Space Agency (ASI), the Norwegian Space Agency (NOSA), United Kingdom Space Agency (UKSA), and Swedish National Space Agency (SNSA), LUMIO is a 12U (20 cm × 20 cm × 30 cm) CubeSat that will be deployed in a quasi-halo orbit around the Earth-Moon L2 point [1]. Scheduled for launch in 2027 following the successful completion of its design and testing phases, LUMIO’s primary objective is to monitor and characterize Lunar Impact Flashes (LIFs) on the farside on the Moon, an area currently unobservable from Earth that avoid ambient light from sunlight reflected by the Earth. This mission leverages the LUMIO-Cam, a highly sensitive optical instrument operating in the visible and near-infrared spectrum (450-950 nm), enabling precise detection and analysis of meteoroid impact flashes [2].

After the successful completion of Phase B in late 2023, the approval of the following phases by ESA marks a critical milestone for the project. Over the coming years, the detailed design and CubeSat development will continue during Phases C and D, culminating in Phase E, which includes the satellite’s launch and operation on 2027/2028.

LUMIO’s operations will address fundamental questions about meteoroid populations and their interaction with the Moon, specifically focusing on filling the current knowledge gap concerning impactors in the millimeter to decimeter size range [3]. By characterizing the spatial and temporal distribution of impacts, the mission will contribute to refining current meteoroid flux models, which are crucial for both space exploration safety and planetary defense. LUMIO’s compact form-factor and autonomous navigation technologies demonstrate the potential of CubeSats in deep space exploration, offering scalable solutions for future missions. Its observations will complement Earth-based studies restricted to the lunar nearside, thus providing a global view of the lunar meteoroid environment.

This work presents recent advancements in modeling the meteoroid environment within the EarthMoon system, aimed at enhancing predictions of LUMIO’s observations. We also detail our latest efforts to link LIF to their sources, such as meteoroid streams or the sporadic background. Furthermore, an update on the LUMIO CubeSat design is provided, highlighting progress in both ongoing scientific activities and the development of the mission payload. Overall, LUMIO’s capabilities hold significant potential for contributing to the field of planetary defense. Two key contributions stand out:

• LUMIO’s real-time detection of meteoroid impacts on the lunar farside will be synchronized with NASA’s Lunar Reconnaissance Orbiter (LRO) [4]. This synergy will allow for precise identification and follow-up analysis of fresh impact craters. By correlating optical observations with LRO’s high-resolution imaging, LUMIO will help validate impact models and enhance understanding of hypervelocity cratering process.

• LUMIO is uniquely positioned to observe the asteroid Apophis during its near-Earth flyby in 2029. This event presents a rare opportunity to study the interaction of a potentially hazardous object with the Earth-Moon system. LUMIO’s instrument will be capable of observing Apophis for nearly one month before its close encounter and 2-3 days after it.

Comments:

Oral presentation preferred, will be attending in person
References

[1] A. M. Cipriano, D. A. Dei Tos, F. Topputo, Orbit Design for LUMIO: the Lunar Meteoroid Impacts Observer, Frontiers in Astronomy and Space Sciences 5 (2018) 29.
[2] F. Topputo, G. Merisio, V. Franzese, C. Giordano, M. Massari, G. Pilato, D. Labate, A. Cervone, S. Speretta, A. Menicucci, E. Turan, E. Bertels, J. Vennekens, R. Walker, D. Koschny, Meteoroids detection with the LUMIO lunar CubeSat, Icarus 389 (2023) 115213.
[3] R. M. Suggs, D. E. Moser, W. J. Cooke, R. J. Suggs, The flux of kilogram-sized meteoroids from lunar impact monitoring, Icarus 238 (2014) 23–36.
[4] M. S. Robinson, S. M. Brylow, M. Tschimmel, D. Humm, S. J. Lawrence, P. C. Thomas, B. W. Denevi, E. Bowman-Cisneros, J. Zerr, M. A. Ravine, M. A. Caplinger, F. T. Ghaemi, J. A. Schaffner, M. C. Malin, P. Mahanti, A. Bartels, J. Anderson, T. N. Tran, E. M. Eliason, A. S. McEwen, E. Turtle, B. L. Jolliff, H. Hiesinger, Lunar Reconnaissance Orbiter Camera (LROC) Instrument Overview, Space Science Reviews 150 (2010) 81–124.

Asteroids are of significant scientific and practical interest, as they represent primordial remnants from the early Solar System. Often referred to as the "building blocks" of planets, these celestial bodies offer unique insights into the processes that governed planetary formation and the evolution of other celestial objects. Additionally, understanding asteroid compositions and orbital dynamics is critical for planetary defense and resource exploration, as many asteroids contain valuable minerals and materials. A promising approach to asteroid exploration involves transferring an asteroid to an Earth satellite orbit using a spacecraft. Capturing an asteroid into a Moon-resonant orbit creates periodic low-energy launch windows, enabling cost-effective spacecraft deployment for prolonged, detailed study. For crewed missions, this trajectory also provides rapid return capabilities in emergencies or during short-duration missions. Furthermore, this method has potential applications for planetary defense, as it allows for altering the trajectory of an asteroid on a potential collision course with Earth, reducing the risk of hazardous impacts.

This paper presents a mission scenario designed to transfer an asteroid with suitable orbital and mass characteristics into a stable Earth satellite orbit. The proposed strategy begins with applying an optimal velocity impulse to modify the asteroid's trajectory for a gravity assist maneuver near Earth. This maneuver places the asteroid into a heliocentric orbit resonant with Earth's orbital period. Key mission parameters are computed to ensure that during each subsequent Earth-Moon encounter, the asteroid's velocity relative to Earth decreases, while its heliocentric velocity remains synchronized with Earth's orbital motion. This synchronization minimizes any velocity increase relative to Earth, ultimately reducing the asteroid’s velocity below Earth's parabolic escape threshold. The mission design involves multiple lunar flybys, which progressively lower the asteroid's velocity and culminate in its capture into a stable Earth satellite orbit. Detailed calculations are presented, including the required initial velocity impulse to redirect the asteroid, the trajectory parameters ensuring resonance between the asteroid and Earth's heliocentric orbit, the sequence of gravity assist maneuvers and their cumulative impact on reducing the asteroid's Earth-relative velocity and the capture conditions and orbital stability following lunar flybys. Additionally, simulation results are presented to demonstrate the feasibility of this method for a sample asteroid with predefined mass and orbital parameters. These results confirm that the asteroid can be safely captured with minimal fuel consumption while maintaining precise trajectory control.

This approach not only advances asteroid science by enabling long-term, close-proximity study but also enhances planetary defense strategies. By redirecting potentially hazardous asteroids away from Earth-crossing orbits, this technique provides a dual benefit: mitigating impact risks and enabling resource utilization.

The paper proposes an approach to designing transfer trajectories of a spacecraft from its initial orbit in the vicinity of the Sun-Earth libration point to near-Earth asteroids. The features of motion in bounded orbits around libration points, as well as invariant manifolds associated with them, open up the possibility of redirecting a spacecraft to trajectories of rendezvous with near-Earth asteroids almost without fuel consumption. The main focus of the research is to develop flight trajectories that involve a spacecraft initially approaching a celestial body and subsequently returning to the vicinity of the initial libration point.
The potentially hazardous asteroids Apophis and 2001 WN5 were selected as target celestial bodies. The next close approaches of these asteroids to the Earth will take place in 2029 and 2028, respectively. It is worth noting that both near-Earth asteroids will first pass near the L2 Sun-Earth libration point before approaching the Earth, and near the L1 after the approach.
The James Webb Space Telescope, the Euclid spacecraft and the Spectrum-Roentgen-Gamma space observatory are spacecraft for which a concept of an asteroid exploration mission is proposed. All three spacecraft operate in orbits near the L2 Sun-Earth libration point. As a result of the construction of invariant manifolds associated with halo orbits of these spacecraft, trajectories have been identified along which these spacecraft can approach the potentially hazardous asteroids Apophis and 2001 WN5. Based on the analysis of obtained trajectories, necessary impulses for the close passage to these celestial bodies were calculated. Trajectories leading to bounded orbits in the vicinity of the L2 Sun-Earth libration point, after asteroids approaching, were also calculated. Preliminary results show that there are a number of possible scenarios for such flights, in which the total cost of the characteristic velocity does not exceed 50 m/s. It is shown that in all cases, all three spacecraft do not leave the area bounded by the so-called Kislik sphere of influence of the Earth – a sphere with a radius of 2.5 million km centered at the center of mass of the Earth.
The proposed concept may be useful for future missions at the libration points of the Sun-Earth system, especially for small spacecraft due to the low fuel costs for such flights.

PDF of abstract included as attachment.

Planetary defense (PD) scenarios present unique mission design challenges compared to typical interplanetary missions. Critically, the target body cannot be selected to conform to predefined science or technology demonstration objectives. Instead, cosmic chance dictates the impending Earth impact, with the orbit of the body strongly influencing the difficulty and complexity of an Earth impact prevention campaign. The semi-major axis (SMA), eccentricity, and inclination of potentially hazardous orbits vary widely and drive the ΔV requirements of space missions for reconnaissance and Earth impact prevention space missions. The histograms in Figure 1 illustrate the expected distributions of SMA, eccentricity, and inclination for a synthetic pool of Earth impactors based on Reference 1. While the mean SMA of impactors is relatively low, the mean inclination and eccentricity are markedly higher than any historical or planned small-body or planetary rendezvous mission outside of New Horizons’ flyby of Pluto.

In addition to potentially challenging orbits, many planetary defense campaigns require or benefit from rendezvous missions, further increasing mission design difficulty as compared to high-speed flyby missions. For reconnaissance missions, rendezvous enables accurate measurement of the impactor’s mass, comprehensive surface mapping, and maintenance of an observing spacecraft at the body, all of which can be critical for a subsequent mitigation mission. Moreover, impact mitigation techniques such as ion beam deflection (IBD), gravity tractor deflection, laser ablation deflection, and some nuclear explosive device (NED) strategies require rendezvous rather than a high-speed encounter. While flyby missions can minimize mission ΔV by timing the encounter at the ecliptic crossing, rendezvous missions necessitate a plane change to the impactor’s inclined orbit and are subject to significant ΔV costs, driving the potential for high propellant demand, long flight times, and stressing the capability of heavy lift launch vehicles. These rendezvous challenges can be exacerbated by high eccentricity, which can introduce phasing challenges and substantial ΔV cost for periapsis lowering or apoapsis raising. On the other hand, the low SMA of most impactors keeps the bodies relatively close to the Sun and is beneficial for solar power.

This work examines the accessibility of rendezvous PD missions given the high degree of variation in impactor orbital elements and the demanding time constraints associated with warning time. Viable mission architectures in terms of launch vehicle and propulsion system combinations that can address different statistical realizations of impactors are established and compared to past space missions. Solar electric propulsion (SEP) system configurations and chemical propulsion are contrasted, demonstrating the benefit of SEP for impactor rendezvous. Furthermore, we illustrate the advantage of gravity assist combinations to reduce propellant demand and assess the compromise between trajectory time of flight (TOF) and propulsion system parameters such as propellant and solar array size for SEP. This evaluation is enabled by application of a stochastic optimization approach that resolves the optimal Pareto front of multiple mission objectives such as minimizing TOF, maximizing delivered mass, minimizing launch vehicle class, and minimizing solar array size for SEP. An example comparison of the optimal trade space between chemical propulsion and SEP for the 80th percentile inclination body in the synthetic population is highlighted in Figure 2.

References:

[1] S. R. Chesley, G. B. Valsecchi, S. Eggl, M. Granvik, D. Farnocchia and R. Jedicke, "Development of a Realistic Set of Synthetic Earth Impactor Orbits," 2019 IEEE Aerospace Conference, Big Sky, MT, USA, 2019, pp. 1-7, doi: 10.1109/AERO.2019.8742172.

Abstract
Keywords: Space debris, Near Earth Orbit, Terminal rocket stage, Mitigation, Hazardous.
Terminal stage in Launch vehicle poses several challenges: space debris, residual propellant and high-pressure gases. Space debris is due to spent terminal rocket stage, explosion or fragmentation of damaged space objects. The increasing space debris leads the risk of collisions with operational satellites, space craft, and even crewed missions. This space debris can damage or destroy the services such as communication; navigation, weather monitoring on Near Earth Orbit (NEO). Also, the re-entry of space debris to earth’s atmosphere cause damage on the ground.
This paper explores the technical approach by using artificial intelligence and machine learning techniques for mitigating the spent terminal stage by controlled venting of hazardous propellants and gases with passivation and disposal systems, minimizing the risk of uncontrolled de-orbiting and controlled re-entry. Also spent terminal rocket stage can use as a orbital platform for short term scientific experiments using three axis control.
Passivation system can effectively mitigate the propellant vapor and high-pressure gases, explosion, fire hazards, contamination of the environment and damage to nearby spacecraft or space assets. Disposal system designed to safely dispose the residual propellant after passivation, preventing ignition or explosion. This is achieved through a cold gas-based control system utilizes the gas bottles isolated from the propellant tank circuit after the main mission. The leftover high pressure gas is utilized for the cold gas-based control system and the leftover propellant is dispensing through the engine. The efficient disposal of the residual propellant and gases from the terminal liquid stage is accomplished through sequential operation of engine valves, thrusters, pyro valves, and solenoid valves controlled by the onboard computer. Artificial Intelligence techniques are used to hazard mitigate the hazards in Near-Earth Orbit (NEO) operations, especially in managing the risks associated with hazardous propellants, gases, and other potential threats. AI can also optimize propellant usage to minimize waste and reduce the risk of residual propellant hazards at the end of the mission. For predictive maintenance, it is proposed to use Long Short -Term Memory (LSTM) neural network methodology. With the use of Isolation Forest Algorithm, any potential threats in real time can be detected. AI system enables continuous monitoring the health of propulsion systems and related components, providing real-time alerts, if abnormal behavior is detected.

The close Earth approach of the Apophis is the first event in which 300 m size asteroid flybys with the altitude lower than GEO ring and the exciting event for mankind. The year 2029 in which the close flyby occurs is designated as “International Year of Asteroid Awareness and Planetary Defence” by the United Nation. Since the flyby occurs only 4 years later, the development of a new spacecraft for the Apophis observation is very challenging from the perspective of both of the cost and the development duration, the Japan Aerospace Exploration Agency (JAXA) is studying about the possibility of Apophis observation in space by using the JAXA operational satellites i.e. 12 satellites.

In this study, the observability from the perspective of visual magnitude, Earth shadow are evaluated in each satellite. The Apophis direction change rate, which affects the actual magnitude in the detector, is also taken into account to evaluate the observability. The JAXA 12 satellites are: 8 Sun-Synchronous Orbit (SSO), 2 Almost Circular Orbit (ACO), 1 High Elliptical Orbit (HEO), and 1 Geostationary Orbit (GEO). Some SSO satellites has long observable time i.e., 1.5 days in maximum because the Apophis direction from the satellite is almost the direction of the normal vector of the orbital plane. HEO satellite has good observability due to the characteristic of the orbit. GEO has the best observability which can observe Apophis all day. The visual magnitude decreases down to 3-4, which will be bright enough to detect by most of optical detector. The direction change rate in each satellite is under 0.025 deg/sec which is very slow and will not affect the actual visual magnitude by detectors.

Many of JAXA satellites has no optical mission component however there is still possibility to observe Apophis by on-board Star Tracker (STT). At the time of writing, we don’t have enough information what kind of detectors can be used for Apophis observation. We also have to consider about the attitude constraint, thermal constraint, power constraint and telecommunication ability of each satellite to determine whether we can observe Apophis by the satellite. We will proceed to confirm the information and study further on the possibility of Apophis observation by JAXA operational satellites.

Low-thrust, long-period asteroid deflection strategies have become a primary focus in planetary defense research. In such strategies, autonomous cooperative navigation for multi-spacecraft landing has been recognized as one of the critical technologies to achieve precise spacecraft deployment on the asteroid surface. However, existing spacecraft autonomous navigation methods based on Simultaneous Localization and Mapping (SLAM) are primarily focused on global surface mapping, resulting in high computational costs. Moreover, due to the sparsity of features, single-spacecraft SLAM exhibits significant mapping errors, which exacerbate local mapping inaccuracies. To meet the requirements of local mapping at landing sites and precise navigation in deflection missions, this paper introduces a novel EKF-SLAM-based cooperative navigation method for multi-spacecraft by incorporating inter-spacecraft relative positioning information into the EKF-SLAM framework. This approach enables accurate local mapping of landing sites and high-precision cooperative navigation while reducing computational costs. The observability of the proposed navigation method is analyzed to confirm its feasibility and effectiveness. Finally, using existing asteroid datasets as a case study, a two-spacecraft landing navigation scenario was simulated, and the performance of the proposed method was compared to that of the conventional single-spacecraft SLAM method, thereby yielding significant improvements in navigation accuracy.

The concept of a ≈10 kg “nanolander” equipped with a customized suite of instruments designed to complement its carrier spacecraft’s science has been proven valuable e.g. with the Mobile Asteroid Surface sCOuT (MASCOT) surface science package on JAXA’s Hayabusa2 mission. MASCOT successfully landed and operated on (162173) Ryugu on October 3rd, 2018, bridging the gap between the results of orbiter instruments and samples returned to Earth. MASCOT2, a photovoltaic-powered long-life derivate was studied in 2015/16 foreseen to be part of ESA’s proposed AIM mission, to be deployed on Dimorphos in advance of DART’s impact. Unlike the primary battery powered MASCOT, it would have been able to support long-term operations allowing to map the 3D internal structure and geophysical properties of the asteroid by ground-penetrating radar and accelerometers. MASCOT2 in the Didymos system served as the basis of self-transfer MASCOT studies which included propulsion to increase flexibility regarding possible restrictions of various carrier missions. Another variant, CALICUT, was studied to be part of a Chinese asteroid mission to the active asteroid, 133P/Elst-Pizarro, aimed at a long-term operation of the scientific instruments, including a camera, a gamma-ray-spectrometer, a wideband ground-penetrating radar, and a MultiScience Package (MSP) containing a magnetometer, a radiometer, an electric field sensor experiment, a neutral density gauge, an accelerometer, and a set of ground penetrators (“Darts”). In order to cope with the lower solar flux at main belt distances, the lander was designed to have almost 3 times the volume of MASCOT but remained at 13 kg integrated mass. A much wider portfolio of further studies has been performed for various proposed small solar system body missions, including fast fly-by support packages e.g. in a flotilla concept for NEOTωIST as well as adaptations for very small host spacecraft, e.g. resources-sharing concepts. ESA’s proposed RAMSES mission – via Hera a “grandchild” of AIM – inspired a fresh interpretation of the MASCOT2 idea benefiting from a decade of progress in instrument development enabling an expanded set of instruments as well as extensive re-use of MASCOT spare parts, to design and build a self-transfer nanolander within a short timeframe in the spirit and haste of a planetary defense mission now only 3 years from launch towards a very brief encounter before Earth; MASCOT took 2 years to develop from PDR to FM delivery. A wide-band ground penetrating radar, a seismometer, a gravimeter, an accelerometer, and the proven instruments of MASCOT would perform this investigation of the suBsurface of Apophis, Seismicity and Tidal forces in EarTh encounter (BASTET). Every potentially impacting NEO will experience the same deflection effects as MASCOT2 would have measured on Dimorphos during and after the DART impact, and it will experience a close Earth fly-by, naturally or after deflection. Thus, every rendezvous reconnaissance mission can benefit from its own investigations of the suBsurface of its Asteroid, Seismicity and Transient effects of Energy Transfers.

This proposed Research article focuses on planning a map for “Economically Feasible” merged method for swift growth in sector of “Asteroid Mining” for metal and mineral’s mining from Outer Space. The most focused point is “Identification of Exploration of Rare Earth” metals and minerals to be identified and processed.

Scientific Rationale of this Proposed Concept is conception of Air flying helicopter design about 400 years ago from Leonardo Di Vinchi, present form of mobile Communication conceived from Nikola Tesla less than 100 years ago, and successful operation of reusable launch vehicle rockets by Tesla. Exercising the motivation to “Conceptualize Out of the Box” thought process this Proposal is scientifically pitched to be developed in due course of time with huge cost curtailing in “Space Mining”.

The Scientific Proposal is mergence of Nine Different Scientific Aspects together. They are as follows:-

1) Existing Rare Earth Metals, Minerals and alloy that are not found on Planet Earth but they Exist.
2) Origin of such Rare earth elements in our Planet.
3) Defending our planet from destructive elements of falling Asteroids and Near Earth Objects.
4) Tap the Asteroid and other revolving “Near Earth Objects”(NEO) in space which may be immense useful for mankind.
5) Proposed Infrastructure and Method for Scientific Installation of “International Asteroids Processing Space Station” with for handling risk and challenges involved in operations of Space Mining.
6) Scientific Study of Properties of Asteroids and “Near Earth Objects” with comparing with existing “Rare Earth Elements” on earth and process as per requirements.
7) Exploring the Energy Sector for developing “Green Energy” and “Sustainable Energy” for planet Earth.
8) Assimilation of Available resources and speedily development of “Research And Development” of Human Capital for rapid growth in Scientific Development of overall Space Mining Sector.
9) Development of new Curriculum related with Innovative Teaching And Research Methods to cater the Demands of content and length of the Proposed Project.

Existing Rare Earth Metal/Mineral Explored.

A real pragmatic visit has been made to one of the oldest Museum Library and the “Unique Preservative” Fossil has been covered as a real case study in form of Primary Data Collection(1). The Proposed Concept will elaborate in details about the methods and steps which will enable to identify the elements of asteroid as well as the various sectors where the “Asteroid Mining” and it’s achieved products can be utilized for mankind in terms of Green Energy Generation, Food Preservation by Peaceful use of Nuclear Technology in Agricultural Sector and elements used in it(2). Also the Rare Earth elements will be a Game Changer for early achieving of Status of “NET Zero”. And also the Model of Preserving the Dangerous Radioactive Substance if any found in “Asteroid Mining” by appropriate models concealing the radiation after disposal.

The details of each of the nine mentioned scientific aspects will be explained scientifically in an elaborated mode in Full Paper Submission with all Scientific Measure and used Technologies.

Please see attached PDF.

The European spacecraft mission HERA is currently flying towards the binary asteroid system Didymos. The spacecraft will arrive in the vicinity of the asteroids at the end of 2026 and thanks to its autonomous vision-based GNC, will be able to fly autonomously down to a distance of a few hundred meters from them. The main purpose of the mission is to characterize the impact of DART (NASA mission) over the surface of the moon of the binary asteroid system. In order to achieve its goal, HERA GNC subsystem has been developed to be highly autonomous. Using a vision-based technology (the Asteroid Framing Camera is used both for Science and for navigation) the attitude guidance is autonomously computed on-board. In the experimental phase of the mission, also the maneuvers can be corrected autonomously, to get as close as possible to the asteroids in safe conditions.

Considering HERA success, ESA is planning another asteroid mission called RAMSES, in the frame of Planetary Defence. The mission objective is Apophis, an asteroid that, on 13 April 2029, will fly-by the Earth at a distance of less than 32,000 kilometers, rendering it visible to the naked eye. RAMSES currently entered its implementation phase and its purpose is to conduct a detailed characterization of the asteroid both pre and post the encounter, to be able to assess the effects of the tidal forces exerted by the Earth during the close passage. This endeavor will provide sufficient data to analyze and predict the likelihood of a potential impact with Earth in 2069.

This paper will focus on the HERA GNC design, and its evolution towards the RAMSES mission needs. A primary difference between the RAMSES and HERA missions is the more constrained dry weight of the spacecraft, as RAMSES needs considerably greater Delta-V for its deep space trajectory. Accordingly, a significant effort has been made to minimize the overall weight of the SC, influencing both the sensor suite available and the fuel budget during proximity operations. Consequently, the redundancy philosophy has been revisited leading to the removal of specific physical unit redundancies, which leads to the implementation of functional redundancies. Furthermore, the proximity operations have been designed to minimize the Delta-V consumption and increase on-board autonomy. As a key difference, Hovering has been proposed for RAMSES aiming the minimization of operational costs and ground effort, and benefiting from an increased AOCS/GNC autonomy.

Performing a stable and robust surface landing on small celestial bodies is essential for future scientific exploration and planetary defense missions. However, in practical missions, due to the weak gravity and complex surface topography, the widely adopted rigid landers are prone to rebound or overturning upon touchdown. This paper reviews a novel landing mode, namely the flexible landing, and highlights the most recent developments in the fields of flexible landing guidance and navigation. The flexible landing employs a flexible lander composed of a soft structure and several embedded rigid nodes to execute the landing mission. Compared with rigid landers, the soft structure, which is made of intelligent materials, increases the contact area between the lander and the surface and dissipates kinetic energy during touchdown, thereby reducing the risks of rollover or rebound.

Despite the advantages in enabling reliable and adaptable surface landing, the flexible lander is inherently an infinite-dimensional system, presenting challenge for the design of guidance, navigation, and control methods. To overcome this challenge, the concept of “equivalent plane” is introduced to establish a state representation model, where the state of the flexible lander is represented by the state of the equivalent plane center, including the center position, velocity and tilt angle. Since the state of the equivalent plane center can be derived from the states of the nodes, autonomous navigation, guidance and control of the flexible lander can be achieved through the estimation and control of the finite-dimensional node states. Building upon this, a cooperative flexible landing navigation method is proposed. During the landing process, the state of the nodes satisfies the flexible deformation constraints. By incorporating such nonlinear inequality constraints to refine the state estimates, a constrained filtering algorithm with theoretically guaranteed performance is developed. Further, the geometric characteristic of the landing trajectory is considered. The curvature guidance is then designed to enable the flexible lander follows a geometrically convex trajectory for landing, facilitating earlier observation of the landing site and improving obstacle avoidance performance.

This time, we have time. 2024 PDC25 takes 16 years, 10 months, 2 weeks, and 6 days from its fictitious discovery to its fictitious impact on Wednesday, April 24th, 2041 – and it will, because this is an exercise! 2021 PDC was not so kind, leaving us only 6 months to play with it. The coming close encounter of (99942) Apophis on Friday, April 13th, 2029, when it will get to within 31650 km altitude over the North Atlantic at 21:46 UT in the night sky of more than a billion people, reminds us that, if it had not been for an exceptional discovery at very low solar elongation – 56° – and very long range – 1.1 AU – for a 370 m object in a midsummer night in 2004, we might well have gotten a shocking Friday 13th naked-eye surprise below geostationary altitude 4¼ years from now instead of an impact probability peaking at 2.7% for Christmas 20 years ago. With 6 months to go, or even 6 years considering from the perspective of a surprise in 2029 the possible 2036 impact of Apophis that took 9 years to rule out completely, who knows what, when a NEO should approach this globe to destroy it, as it often has been and will be destroyed, we could tear from its foundations by means of ingenuity and improvisation, to hurl masses, as Deep Impact and DART have done, against the piled rubble? Well, for starters, we are good at churning out the same stuff all over again and again from assembly lines – known as armory practice before it came to Detroit. Nearly a century after the Springfield Rifle, the U.S. alone built over 300,000 airplanes during the 6 years of World War II. Today, the world builds more than 85 million cars a year, and more than 1.4 billion mobile phones. One company alone built over 7500 satellites and put them into orbit with over 215 launches, within 6 years, and thousands more are planned, also by other space service providers. Although the detailed design of these spacecraft is proprietary, sufficient public information exists to derive their approximate properties and capabilities, and to lay out a feasibility study of last-ditch attempts to save Earth from a near-term large impact on the scale of the PDC Exercise targets or their notorious leftovers aimed at the participating civil defense and disaster management communities, and a location conveniently close to the conference center. With lead times ranging from several months to a few years to impact, the adaptation and development potential spans the range from shoot and hope straight off production lines accelerated to the very limit, to largely mission-specific redesign based on the now-term technology of the day, in global synergy of planetary science and planetary industry working hand in hand to grind down an approaching asteroid in space by a long series of somewhat DART-like impacts. And then we shall have traditions of tycoons and telescopes again, and of wars with rocks.

Rapid reconnaissance flyby missions represent the fastest means of characterizing a potentially hazardous asteroid in a planetary defense scenario. Flyby trajectories can often reach the asteroid with launches every year and cruise durations as short as months. In these scenarios, the design, fabrication, and testing of the spacecraft is the longest duration event in the overall timeline. In an effort to achieve a faster response capability and shorten this timeline, we could consider developing the spacecraft and instrument suite in advance of the asteroid’s discovery. This would even offer an opportunity to test and demonstrate the spacecraft prior to a critical threat when any mission failures could be catastrophic.

This study seeks to characterize the mission design requirements and trade-space for a flyby spacecraft capable of performing reconnaissance of an as-yet undiscovered threat. Our goal is to help define a set of requirements the spacecraft must meet in order to be applicable for some percentage (e.g. 90%) of the expected threat population.

Our approach is to use a synthetic population of threatening asteroids to represent the distribution of expected orbital properties. For each synthetic asteroid, we compute the set of feasible ballistic (no maneuver) spacecraft trajectories that reach the asteroid. This ensemble of trajectories is then post-processed to identify subsets of parameters that correspond to satisfy fractions of the asteroid population. As an example, spacecraft power engineers must size the solar arrays to the maximum solar distance the spacecraft will experience. With this set of trajectories, we can compute the maximum spacecraft aphelion solar distance that is compatible with feasible trajectories to 90% of the synthetic population. The same type of question can be addressed for most relevant mission design parameters: encounter flyby speed; encounter lighting geometry; solar distances; Earth distances; and angles between the Earth, Sun, and asteroid.

Many of these parameters are highly correlated. An example of this correlation is shown in Figure 1 for solar phase angle and encounter flyby speed. The colors indicate the fraction of all synthetic targets that are reachable with at most the specified speed or angle. The dotted lines are contours of 80%, 90%, and 95% of the population.

{fig1.png}
Figure 1: Approach solar phase angle versus flyby speed for the synthetic threat population. Previous asteroid (upside down pink triangles) and comet (green triangles) flybys are also plotted. This figure also appears in [1].

It turns out that there are multiple combinations of requirements that are compatible with 90% of the population. Table 1 gives one such set of parameters. Any individual flyby is unlikely to require all of the listed conditions. However, we don’t know which conditions a newly discovered asteroid will require in advance. That is, the spacecraft is overdesigned for any single asteroid.

{table1.png}

We conclude by presenting different sets of parameters that achieve 90% completeness, and identifying which parameters are most driving.

The Kalkkop Crater, located in the Eastern Cape, South Africa, is a deeply eroded small impact structure that was filled with lake sediments following the impact event and formed at approximately 250 ka [1]. The crater was initially drilled for petrophysical studies [2], then later re-investigated to confirm the impact hypothesis [3]. The crater was assumed to have a simple crater morphology, based mainly on the surface expression. In this study, we re-investigate the Kalkkop crater using a new, 89 m drill core taken from the center of the structure with the purpose of studying post-impact lake sediments, as well as remote sensing for multispectral analysis of the impact site, drone images to generate a high-resolution digital elevation model (DEM), and geophysical techniques, including electrical resistivity tomography (ERT) and audio magnetotelluric (AMT) techniques to image the subsurface. We have identified previously unreported surface morphological features that define the outer boundaries of the lake sediments and the outer areas of structural deformation related to the impact event. The geophysical results show a zone of low resistivity extending to the lowermost portions of the imaged subsurface. Below the outer extent of the lake sediments, the subsurface transitions to a complex zone that extends to a depth of approximately 80 m below the surface, likely corresponding to listric faults. We interpret the results as reflecting a terraced morphology (e.g., “inverted sombrero”) rather than a simple crater morphology (Figure 1). The crater infill is consistent with protracted sedimentation overlying impact-generated breccia. Previous work had assumed that the crater floor was encountered at depth, but our new results suggest that the drill cores were in fact passing through large blocks within the fallback ejecta. The diameter of the Kalkkop crater was previously reported as 600 m in diameter, but based on our new results, the crater has a maximum diameter of 1600 m. The Kalkkop Crater has implications for the consequences of impacts into layered target rocks in terms of crater formation and post-impact processes.

References
[1] Koeberl C., Reimold W.U., Shirey S., and Le Roux F. 1994. Kalkkop Crater, Cape Province, South Africa: Confirmation of impact origin using osmium isotope systematics, Geochimica et Cosmochimica Acta, Vol. 58, 1229-1234. [2] Blignault J., Rossouw P., De Villiers J., and Russell H. 1948. The Geology of the Schoorsteenberg Area, Cape Province. Geological Survey of South Africa, Explanation of Sheet No. 166. Pretoria, South Africa. [3] Reimold W.U., Le Roux F., Koeberl C. and Shirey, S. B. 1993. Kalkkop crater, Eastern Cape-A new impact crater in South Africa. Lunar and Planetary Science XXIV, 1197- 1198.

Figure 1: The terraced crater in the Arcadia Planitia region of Mars compared to the ERT results of this study. The profile through the middle of the crater reflects the interpretations given by [3] based on drill core analysis. The crater is best explained as a terraced morphology.

Solar System objects impact Earth’s atmosphere daily, but their small size makes them undetectable before atmospheric entry. To better understand these impactors, we need multi-instrument observations of their disintegration phase [1].
In this study we explore several methods of measuring the pre-atmospheric mass of meteoroids with well-known trajectory, at the source of ton TNT-scale atmospheric impacts [2]. On this scale, the impact is less likely to cause an airwave signal which can be detected instrumentally, or the estimation methods carry high uncertainty [e.g. 3, 4], hence, their mass is poorly constrained.
To assess the robustness of the energy estimation methods, we first collected meteoroid-derived measurements from the literature. We found that the radiation of the object is the most commonly measured property of the event [2]. Thus, the analysis focused on the optical energy signature of the objects. Most of the bolides did not have their total radiated energy estimated, hence, this was obtained based on the published light curve. Next, their kinetic energy was computed based on given estimates
of velocity and mass.
We derived an empirical relation between source energy and optical energy. We found a good correlation between entry kinetic energy and light radiation during deceleration, which holds regardless of fragmentation and ablation profiles.
The next step would be to extend this relation to more frequent, lower-energy impactors, and use it to calibrate complementary equipment (e.g. radiometers [5] or lightning mappers), to constrain size-frequency distribution of atmospheric impacts.

References
[1] F. Colas, et al., FRIPON: a worldwide network to track incoming meteoroids, Astronomy & Astrophysics 644 (2020) A53.
[2] S. Anghel, et al., Energy signature of ton TNT-class impacts: analysis of the 2018 December 22 fireball over Western Pyrenees, Monthly Notices of the Royal Astronomical Society 508 (2021) 5716.
[3] W. N. Edwards, et al., Estimate of the radiative power of bolides based on optical and infrasonic records, Journal of Atmospheric and Solar-Terrestrial Physics 68 (2006) 1136.
[4] T. A. Ens, et al., Infrasound production by bolides: A global statistical study, Journal of Atmospheric and Solar-Terrestrial
Physics 80 (2012) 208.
[5] J. L. Rault, F. Colas, Radiometry of meteors, arXiv 1911 (2019) 04290

Near Earth Objects (NEOs), such as asteroids on an Earth-impact trajectory, are low probability, high consequence natural hazards. To understand the consequences of Earth-impacting NEOs we rely on numerical simulations to model potential damage. In this study we investigate asteroid ocean impacts, focusing on the primary and secondary hazards such as tsunami wave generation and atmospheric effects. Our main objective is to develop a methodology that transitions the local, early-time effects of an asteroid impact - captured using a high-fidelity hydrocode - into models capable of simulating secondary hazards over extended timescales and large distances.

We employ ALE3D, a multi-physics hydrocode utilizing an Arbitrary Lagrangian-Eulerian (ALE) scheme, to simulate impacts of asteroids with diameters of 75m, 125m, and 200m into water depths of 1km and 3km. This hydrocode effectively models asteroid fragmentation, water crater formation, complex thermodynamic behaviors, vaporization, and the conversion of impact energy into wave energy, all on microsecond time scales. Once the initial impact effects are captured, the simulation data is linked to a Boussinesq tsunami propagation model, FUNWAVE, and a Weather Research and Forecasting model, WRF. These models are used to calculate secondary hazards, such as tsunamis and atmospheric response, on a regional scale over hundreds of seconds.

This research aligns with the 2023-2032 Planetary Science & Astrobiology Decadal Survey's recommendations to establish an operational capability for threat assessment and rapid information dissemination through a national planetary defense pipeline. Given the limited historical data on NEO impacts, theoretical numerical models offer valuable insights for hazard assessment and emergency response planning. If an asteroid is detected early enough, these models can inform decisions on reconnaissance or mitigation missions. By comprehensively modeling these cascading hazards, this study enhances our understanding of the risks posed by ocean impacting NEOs and informs the development of effective mitigation strategies.

Lawrence Livermore National Laboratory is operated by Lawrence Livermore National Security, LLC, for the U.S. Department of Energy, National Nuclear Security Administration under Contract DE-AC5207NA27344. LLNL-ABS-871476.

Introduction: Asteroid impacts can cause varying levels of damage across different areas, largely depending on the energy of the impactor. The complex processes that cause damage are not limited to the initial effects. First-order effects (those that are triggered directly) such as blast waves, craters, ejecta plumes, seismic activity, and thermal radiation have been the primary focus areas of planetary defense studies [1-4], while second-order effects are still relatively poorly characterized [5]. Such cascading hazards could persist for years post-impact, and our understanding of them may be significant to long-term mitigation planning and recovery strategies. Downstream post-impact flooding has been predicted from the more common and well-understood terrestrial wildfire-flood sequence [5]. Thermal radiation due to impact is proposed to be analogous to wildfire effects, which causes hydrophobic damage to the surrounding soils, leading to an increase in precipitation runoff and consequently raising downstream flooding risk.

Approach: This work uses GeoCLAW, a model that solves the shallow-water equations [6], to evaluate potential downstream flooding events and assess their probability, magnitude, and relevance to flood risk assessment. A research framework was developed using a hypothetical impact scenario derived from the 2023 PDC (Planetary Defense Conference) risk corridor [7]: an 800 m-diameter asteroid impacting into the Dallas-Fort Worth area of Texas [8]. Estimates of the exposed and affected population were compared across different rainfall rates and the extent of soil surface hydrophobicity, induced by impactor heat. This comparison aimed to evaluate the influence of each factor on overall flooding risk. This methodology is then also applied to the 2025 PDC scenario’s roughly 200 m-diameter asteroid impact, providing contrast to the Texas case study, with significantly varying topography, infrastructure, and precipitation regimes present.
Current Application: This study compares two impact sites – one near Cape Town, South Africa (a coastal region with floodplains surrounded by mountains) and another upstream of Bucharest, Romania (a mountainous region with high drainage density) – to better understand when and where downstream effects may be more hazardous than initial effects. The findings emphasize situations where large population centers are located downstream from impact sites in less-populated areas. By determining the differences in flooding severity between these events, we can more accurately characterize the influence of impact location on local factors. These assessments aim to increase preparedness for such events, streamlining the evaluation of downstream flooding risk significance based on geography and predicted impactor attributes.

References:
[1] Hills, J., & Goda, M. (1993) AJ 105(3), 1114–1144.
[2] Collins, G. S., Melosh, H. J., & Marcus, R. A. (2010) MPS 40(6), 817–840.
[3] Mathias, D. L., Wheeler, L. F., & Dotson, J. L. (2017) Icarus 289, 106–119.
[4] Rumpf, C. M., Lewis, H. G., & Atkinson, P. M. (2017) GRL 44(8), 3433–3440.
[5] Titus, T. et al. (2023) NH 116, 1355–1402.
[6] Berger, M. J. et al. (2011) AWR 34(9), 1195–1206.
[7] Wheeler, L. et al. (2024) AA 216, 468–487.
[8] Titus, T. et al. (2023) IAA-PDC.

Near-earth objects pose a significant threat to humanity, potentially impacting a profound disruption beyond our imagination. Like volcanoes, NEO also played a significant role in shaping the surface of our planet. Whether they explode above the ground or reach the surface, NEO impacts have done significant damage. In 2013, an asteroid about 18 m in diameter called Chelyabinsk exploded while still in the air and released about 500 kilotones of energy. Though the impact didn’t cause much damage, but made us think again about our planetary defence mechanisms and also challenged our understanding of the asteroids. Where we put an asteroid around 140 m as the potential hazardous object (PHO) Chelyabinsk impact proves otherwise.
With this research, we analyse our understanding of asteroids and their classification, identifying the possible threat and likelihood of impact alongside the consequences of impact while providing references from case studies of previous impacts. We studied impact effects, like physical damage, environmental effects, and social and economic effects. With the help of hypothetical scenarios, we have calculated the probability of asteroid impact and factors influencing these probabilities.
With this in consideration, we also develop post-impact assessment and recovery Strategies. We used previous impact post-recovery case studies to analyse the scenario and designed our strategies for post-impact recovery. We assess the extent of damage on both social and economic fronts. We included strategies for rebuilding infrastructure and restoration services. While developed nations hold resources to assess the risk and develop technology to reduce the impact and recover from post-impact damage, developing or underdeveloped nations will be at major risk. To deal with these, we also examine the role of international corporations in the asteroid impact risk assessment and collective efforts to provide support to affected areas. We also discussed the need for international policies and governance frameworks to address asteroid impact risk. With this in mind, we can analyse the risk, reduce the impact damage, and recover with minimum damage post-impact

Near-Earth object (NEO) impacts pose a significant risk to the Earth, with potential consequences ranging from localized destruction to global-scale environmental disruptions. A critical aspect of NEO consequences is the vapor and ejecta distribution, which can cause environmental consequences far from the impact site and even globally due to atmospheric effects. Using a suite of 2D and 3D numerical hydrocode impact simulations, we investigate how the volume and composition of vapor and ejecta during NEO impacts depends on impactor properties (size, velocity, composition) and the Earth’s surface materials (continental crust, oceanic water, or mixed targets). We utilize new equations of state and the newly updated ROCK strength model in the CTH hydrocode, and test how strength parameters affect model results. We examine a range of impact parameters and determine the dispersal pattern of ejecta and the amount of material deposited into the Earth’s atmosphere. We examine both impacts where the projectile penetrates the Earth’s atmosphere and impacts the surface, and impacts where the projectile burns up within the atmosphere. Our results will provide insight into the far-field and localized/global atmospheric effects of NEO impacts, which is critical for improving predictions of environmental and societal risks posed by potential NEO collisions.

In recent years, eleven small near-Earth asteroids were discovered a few hours before colliding with Earth. They were all about one meter in diameter and they all disintegrated in the atmosphere, generating bright fireballs without causing damage. In some cases – namely 2008 TC3, 2018 LA, 2023 CX1, and 2024 BX1 – several meteorites have been recovered. In cases like these, it is not always possible to triangulate the fireball generated by the asteroid fall as taken by on-ground cameras to circumscribe the strewn field position. For this reason, it is important to compute a strewn field ab initio [1], i.e. by propagating the asteroid trajectory in the atmosphere starting from the initial conditions at 100 km altitude obtained directly from the heliocentric orbit, coupled with some reasonable hypotheses about the mean strength and the mass of the fragments to sample the strewn field.

By adopting a simple fragmentation model and a real atmospheric profile, useful results can be obtained to locate the strewn field, as we showed for the recent falls of asteroids 2023 CX1, 2024 BX1 and the historical case of 2008 TC3. It was possible to locate the strewn field of our study cases with an uncertainty of the order of one kilometer with a mean strength in the range 0.5 - 5 MPa and the mass of the possible final fragments in the range 1 g - 1 kg. We finally give possible strewn fields of two other recent asteroids discovered before impact: 2022 WJ1, impacted near Toronto, and 2024 XA1, impacted over the Sakha Republic (Russia) [2].

[1] Carbognani et al. (2025), Ab initio strewn field for small impacting asteroids, Icarus 425
[2] Gianotto et al. (2025), The fall of 2024 XA1 and the location of possible meteorites, submitted for publication

Keywords: Planetary Defense, Post-SDGs, fundamental connection, the Year 2025, Apophis,

The Sustainable Development Goals (SDGs), adopted unanimously by United Nations member states at the General Assembly in September 2015, represent a set of international goals aimed at creating a sustainable and better world by 2030. Considering the significance of the SDGs, several space-related challenges are intrinsically linked to their objectives. Among these, planetary defense, which addresses the survival of humanity and its civilization, shares a fundamental connection with the SDGs.
However, the current SDGs do not explicitly include planetary defense and other space-related challenges, and any connection to these issues must be inferred indirectly. This omission can be attributed to two main reasons. First, the discussion on asteroid impacts at the United Nations has been delayed. A key turning point in this context was the 2013 Chelyabinsk meteor event in Russia, which highlighted the catastrophic potential of extraterrestrial impacts. Nonetheless, the timing was too late to influence the incorporation of space-related issues into the SDGs. Second, scholars and practitioners engaged in space-related fields have not yet sufficiently advocated for the integration of such issues into the SDG framework.
As the 2030 deadline for the current SDGs approaches, international discussions have begun on envisioning the "post-SDGs" framework. This presents a significant opportunity to include space-related challenges in the next iteration of global goals. A major milestone in this process is the UN SDGs Summit scheduled for the autumn of 2027, during which the outline of the post-SDGs agenda may be developed. The adoption of the new SDGs framework is expected at the 2030 UN General Assembly. Additionally, the close approach of the asteroid Apophis in April 2029 could serve as a meaningful event to garner global attention on planetary defense.
Among the space-related challenges to be included in the SDGs, planetary defense is of paramount importance. Many aspects of this issue and its countermeasures have already been extensively discussed at the Planetary Defense Conferences (PDCs), providing a valuable foundation for narrowing down priorities. Beyond planetary defense, other space-related challenges intersect with the SDGs, such as the impact of solar flares on Earth, space debris management, sustainable space development on the Moon and Mars, the utilization of space for energy solutions, and so on.
Given the timeline for the post-SDGs agenda, the year 2025 emerges as a particularly critical juncture. It is essential to capitalize on numerous opportunities to strengthen efforts toward realizing SDGs that include planetary defense and other space-related challenges.

In 2018, a scandal in the space industry raised legal questions that still concern the legal community today. In January of that year, a US start-up launched four Cube satellites using an Indian rocket without holding an FCC license to use communications technology on these satellites. While this illegal use of the satellites was ultimately punished with a $900,000 civil penalty, it nevertheless raises the question of whether the current space regulations are not sufficient to prevent rogue space actors from potentially taking action in a planetary defence situation without the authorisation of the State.

Why is this a problem? The sad reality is that in many planetary defence scenarios, some States may be reluctant to participate in mitigation efforts. This reluctance may be connected to the political implications associated with a State's use of a nuclear device, as well as the liability the State faces should the mission fail in part. In comparison, we have seen an increase in private actors that are not necessarily as risk-averse as some States. These private actors are now an integral part of any potential planetary defence missions, for example, considering the reliance on SpaceX launch capabilities noted at the previous Planetary Defence Conference in 2023. Therefore, the idea that a private actor could intervene in the event of a NEO threat instead of a State, without the authorisation of the State, is no longer as irrational as it may have been in the past, noting the actions of Swarm technologies in 2018. This action, in turn, could have serious consequences for the State, as it would still be responsible and liable should the mission partially fail.

This presentation for the 2025 Planetary Defence Conference will show how national legislation has regulated the idea of ‘Rouge Space Actors.’  The launch procured by Swarm technologies in January 2018 will be used as a case study to see how such a space actor has been dealt with in the past. This response is then applied to a planetary defence mission, considering if current legislations are sufficient to take action against ‘Rouge Space Actors.’

Keywords: Planetary Defense Ethics, Extramilitary Domain

Age-old concepts of sovereign military power have traditionally transferred into new physical and technological domains (e.g., air, undersea, electromagnetic spectrum) to create security. However, some recent emerging threat domains have been excluded from nations’ military responsibility. Two current examples are cyber security and planetary defense. By addressing these topics outside of the military context and associated treaties, laws, and ethics; states, organizations, and individuals are developing new methods of defending their interests.

Across the globe, companies must defend themselves against cyber security attack from outside their country’s borders with no assistance from their government’s military defense. Cyber security is treated more like a natural disaster with attendant insurance, civil agencies, and remediation industry. Organizations have also developed industry-based Information Sharing and Analysis Centers (ISACs) to pool information and resources. The resulting cyber security ethical frameworks are based on professional codes, technology considerations, and applicable laws.

Planetary defense is another extramilitary domain with many parallels to cyber security. Information sharing and analysis is a critical aspect of the field and requires cross-organizational collaboration. The threat is more likely to be adequately addressed as a mutualized risk than by each individual alone. In addition, the threat manifests from an extraterritorial location (like a cyber advanced persistent threat) so it is not readily affected by legal sanction.

This paper explores the potential benefits of using cyber security ethical and cooperation frameworks to inform the field of planetary defense. It also highlights pitfalls in using climate change-related parallels with planetary defense based on systemic and political factors. The resources applied to cyber security are orders of magnitude greater than planetary defense. To the degree that cyber security investment’s benefits are transferable they should be leveraged by other threat domains.

Planetary defense represents a unique socio-ethical and legal challenge being simultaneously everyone’s responsibility and no one’s. A robust planetary defense strategy depends not only on developing technological capabilities but balancing regional and global political interests and creating a “mandate to act” in the case of an impact hazard. Planetary defense activities have the potential to exacerbate political tensions due to the general mistrust between countries from potential dual-use capabilities of planetary defense systems. Outer space is often considered the ultimate “high ground” with Praẑák (2021) noting it already provides “reconnaissance, secure, telecommunications and space situational awareness for both civilian and military uses." Ideally, planetary defense would be treated like weather-related disasters and bring countries together for the "common altruistic good" but the reality can be quite different in this area. This paper will argue that a multilateral agreement for the protection of Earth and the astro-geophysical environment would promote space cooperation, protect our space heritage, and mitigate potential conflict related to planetary defense activities. It considers recent advances in planetary defense science and then applies principles of space law and ethics to evaluate how best to create a global response in the event of a predicted cometary or asteroidal impact.

Keywords: planetary defense, reconnaissance mission, asteroid impact, NEOs

If an asteroid or comet is found on a potential Earth-impact trajectory, a top priority should be to reduce uncertainties in whether the object will impact the Earth and in the potential consequences of the possible impact. Ground- and space-based telescopes will provide essential data for reducing some uncertainties. A reconnaissance spacecraft mission, however, can provide key information that cannot be obtained through other methods. Such information can slash uncertainties about the possible impact, thereby improving planning for both consequence management and space missions to prevent Earth impact.

The value of spacecraft reconnaissance missions is well established [1,2,3] and documented in relevant reports from the U.N.-endorsed Space Mission Planning Advisory Group (SMPAG) [2] and in the United States’ Report on Near-Earth Object Impact Threat Emergency Protocols (NITEP) [3]. Both SMPAG and NITEP recommend that planning of space mission options begin once there is a >1% probability that an object characterized to be greater than 50 m in size will impact
within 50 years [2,3].

Beyond that, the U.S. NITEP and SMPAG recommendations diverge. SMPAG does not recommend thresholds for implementing (as opposed to planning) mission options. The NITEP , in contrast, states that if the previously mentioned thresholds for mission options planning are met, then “if time before impact permits–the United States should proceed quickly with a reconnaissance mission, in cooperation with international partners if possible.” [3] NITEP briefly discusses the cost/benefit analysis of reconnaissance missions [3], but lacks recommendations about the
particulars of implementing a reconnaissance mission. Specifying recommendations will streamline discussions about courses of action in the event of an actual impact threat, thereby saving time in a potentially time-sensitive situation.

We propose that the organizations who provide guidance about planetary defense mission options adopt the following pragmatic recommendation for reconnaissance missions: When the SMPAG thresholds for mission option planning are crossed and when warning time is sufficient, one or more space agencies should implement whatever type of reconnaissance mission will provide actionable information the soonest. This time-sensitive information is critical to have in hand to inform consequence management and, if needed, Earth impact prevention missions.

Both purpose-built and repurposed spacecraft missions (e.g., redirecting an existing spacecraft) should be considered. If a suitable spacecraft can rendezvous with the threat object sooner than a flyby mission can reach it, then a rendezvous mission is preferable due to its higher characterization fidelity. A yearning for better data should not delay the timely collection of actionable data.

[1] NASEM. 2023. Origins, Worlds, and Life: A Decadal Strategy for Planetary
Science and Astrobiology 2023-2032. Washington, DC: The National Academies
Press. https://doi.org/10.17226/26522.
[2] Recommended criteria & thresholds for action for a potential NEO impact threat,
SMPAG-RP-003/1.0, 2018 Oct 18.
https://www.cosmos.esa.int/documents/336356/1879207/SMPAG-RP-003_01_0_Thr
esholds%26Criterion_2018-10-18.pdf/58eb84ae-e3b6-1b08-9465-d25c548c5c9b
[3] NSTC, 2021, Report on Near-Earth Object Impact Threat Emergency Protocols.
39 pages.
https://trumpwhitehouse.archives.gov/wp-content/uploads/2021/01/NEO-Impact-Thre
at-Protocols-Jan2021.pdf

The Space Mission Planning Advisory Group (SMPAG) is one of the two UN-endorsed groups that deals with the asteroid impact threat. The other group is called International Asteroid Warning Network (IAWN). SMPAG members are space-faring nations, and their task is to discuss how a space-based response to an asteroid impact threat could look like [1].
The critera for SMPAG to become active are:
• The asteroid must have at least 50 m in size, or a corresponding absolute magnitude;
• The expected impact probability must be larger than 1 %;
• The expected impact must be within 50 years from now.
These requirements were exceeded in the fictional (!) asteroid threat scenario set up for this conference.
SMPAG had received the official warning on 01 Aug 2024 and discussed, as if this were real, possible reactions of space agencies. This was done via regular teleconferences every Friday, and a final in-person session at a meeting in Milano, Italy, on 10 + 11 Oct 2024. The recommendation was provided back to the exercise planning team to prepare a second epoch of the simulated threat scenario.
It will also be distributed to decision makers for feedback. After receiving the new epoch 2 scenario, SMPAG will again work on coordinating the tasks to be done by space agencies. The results will be presented to the ’decision makers panel’ at the PDC2025.
In this presentation, we will give more details on how the exercise was implemented in the ongoing SMPAG work to define their work. In particular, it will give information on the lessons learned - what is working well, what is not yet working well, where do we need additional procedures defined, and more.

Please find the abstract in attachment.

The 2025 Planetary Defense Conference (PDC) hypothetical asteroid impact threat exercise is being conducted in coordination with the United Nations-endorsed Space Mission Planning Advisory Group (SMPAG), enabling an exercise of SMPAG’s process for producing technical recommendations for space mission options using inputs received from space agencies in participating nations. In this paper, we describe the work performed for this exercise by the NASA-led team.

We will discuss our methodology for assessing space mission options to respond to the hypothetical asteroid threat scenario, including reconnaissance missions and Earth impact prevention missions. For reconnaissance, we assessed flyby and rendezvous options and we included both re-tasked extant spacecraft and purpose-built spacecraft. Detailed results for analysis of re-tasking extant spacecraft for reconnaissance will be presented in a related paper. Fig. 1 shows some exemplar reconnaissance mission options. For Earth impact prevention missions, both asteroid deflection and robust disruption of the asteroid are considered, and the following mission types are assessed: ion beam deflection, kinetic impactor deflection and disruption, and nuclear explosive device deflection and disruption. Fig. 2 shows some example trade space evaluations for several deflection mission types.

We will also summarize simulation studies performed to 1) ascertain how much change-in-velocity ($\Delta v$) an asteroid can tolerate before fragmentation onset, and 2) establish requirements for robustly disrupting an asteroid, i.e., breaking it into small and widely scattered fragments posing little to no residual Earth impact risk. Detailed results of these simulation studies will be presented in a related paper and some example simulation outputs are shown in Fig. 3. The $\Delta v$ required for asteroid deflection as a function of time is shown in Fig. 4. Heuristics informed by the simulation results are incorporated into optimization of multi-action deflection mission campaign options that spread the total deflection impulse across multiple smaller impulses as a strategy for avoiding asteroid fragmentation during deflection. Studies were also performed assessing the minimum amount of time required between deflection impulses to measure the effects on the asteroid’s orbit before the next impulse. Details of that study are presented in a related paper.

We assessed mission options at two epochs in the scenario timeline: Epoch 1, about two months post-discovery when Earth impact probability climbs above the 1% threshold for SMPAG activation and large uncertainties in asteroid physical properties and Earth impact location drive large uncertainties mission requirements; and Epoch 2, just after a flyby reconnaissance mission has reconnoitered the asteroid, significantly reducing uncertainties in asteroid physical properties and Earth impact location and thus enabling more precise assessments of mission options.

Finally, we will summarize the results we provided as inputs from NASA to SMPAG for integration with all such results from other space agencies participating in this exercise. We also make some observations about useful generalizations from these results with potential applicability to any planetary defense scenario.

In planetary defense exercise scenarios, most discussions of rapid response reconnaissance missions focus on dedicated spacecraft. These are typically new spacecraft, designed and built specifically for the purpose of surveying a newly discovered asteroid that is potentially threatening Earth. A new reconnaissance spacecraft takes approximately three to five years to reach the launch pad, and then still has to travel months or years to reach the asteroid. As an alternative to a new spacecraft, we consider spacecraft already in flight that could potentially be redirected from their original missions to instead survey the hazardous asteroid.

Retasking a spacecraft has the potential to be much more responsive while saving development costs. However, it requires case-by-case analysis of each in-flight spacecraft to determine if it has a sufficiently capable propulsion system with enough propellant and adequate thrust capacity to reach the hazardous asteroid. Additionally, the redirection trajectory must not violate any spacecraft hardware limitations such as minimum or maximum solar range. Even when redirection is possible, additional analysis is required to determine if the payload suite, likely designed for a different use case, can be adapted for planetary defense reconnaissance.

In this work, we examine the feasibility of retasking in-flight NASA spacecraft (OSIRIS-APEX, Lucy, and Psyche) for two exercise scenarios: the Interagency Table Top Exercise #5 held in April, 2024 (NASA PDCO, 2024), and the PDC 2025 hypothetical exercise. In both exercises, we found that it is possible to redirect one or more spacecraft to fast flybys of the exercise asteroids. Figure 1 shows one such solution for redirecting OSIRIS-APEX to a fast flyby of the PDC 2025 hypothetical asteroid. OSIRIS-APEX would be able to reach the asteroid by retargeting the upcoming Earth gravitational assist. In this case, the final arrival time is similar to that of a dedicated, newly built flyby spacecraft. Figure 2 shows the expected performance of its instrument suite in the high-speed flyby, assuming a 50th percentile (by mass) asteroid. The analysis indicates that, despite the instruments being designed for a rendezvous mission, they could potentially detect the asteroid as early as 4 days prior to the encounter and return roughly 1 m resolution from a 100 km flyby distance. In this scenario, OSIRIS-APEX would be useful for adding redundancy to an already planned dedicated flyby spacecraft and by augmenting the in-situ data set to improve the global shape model.

We conclude by discussing the pros and cons of retasking spacecraft, including when the decision to redirect has to be made and how each spacecraft may or may not be suited for retasking.

Figure 1: Candidate trajectory to redirect OSIRIS-APEX to a fast flyby of 2024 PDC25 for the PDC 2025 exercise.

Figure 2: Expected performance of OSIRIS-APEX’s PolyCam for the 50th percentile asteroid for the PDC 2025 exercise.

Acknowledgements:
We would like to thank Kevin Berry and Steve Snyder for their assistance in providing details about Lucy’s and Psyche’s remaining capabilities.

The growing interest in addressing asteroid threat scenarios is justified by current estimates of the Potentially Hazardous Objects (PHOs) population and by recent impacts on Earth. Since 2015, exercises involving hypothetical hazardous asteroids have been proposed, with various solutions discussed during Planetary Defense Conferences (PDCs). This paper presents and analyses preliminary mission design options for the mitigation of asteroid “2024 PDC25”, focus of the scenario introduced for the PDC 2025. To significantly enhance the knowledge of the asteroid’s properties and inform the design of deflection campaigns, impulsive fast fly-by and low-thrust rendezvous reconnaissance mission options are developed. The Single and Multiple Kinetic Impactor (KI) deviation strategies are analysed, leveraging the results from the DART mission. Uncertainties in various parameters are subsequently incorporated into the developed model. Among all elements, the variation of the momentum enhancement factor on the resulting deflection, after one or more impacts, strongly influences the variability of other aspects involved in the physical problem. Based on this analysis, a set of successful and unsuccessful missions are identified. A successful mission would imply the ability to modify the trajectory of the asteroid, while preventing its fragmentation, but it may not guarantee a deviation of at least two Earth radii. Although the KI is the only flight-proven deflection strategy, it does not always represent the most suitable option. Based on the provided estimates of the asteroid size and mass, different percentile cases are identified. For percentile levels associated with particularly small or large masses, neither the KI nor the Multiple KI are capable of fully deviating the asteroid. Other strategies with a lower Technology Readiness Level (TRL) proved to be more effective for a wider range of percentile cases. Nuclear Explosive Devices (NEDs) provide the highest energy density among all deflection techniques, making them a viable impulsive alternative to Kinetic Impactors. A model is developed for Single and Multiple NEDs in a "Carrier" configuration, which offers redundancy and divides the total ∆𝒗 into smaller, controlled impulses to prevent asteroid fragmentation. Specifically, each impulse is kept below a small percentage of the asteroid's surface escape velocity. Given the sufficiently large warning time available, models of slow push/pull deflection strategies are developed and applied to this specific scenario. A preliminary design of deflection missions is therefore proposed for Single Standard, Enhanced and Multiple Gravity Tractor, Single and Multiple Laser Ablation, Single Ion Beam Deflection (IBD) and a newly developed technique of Multiple IBD in Formation Flying. The results are compared, and the most effective deviation strategies for asteroid “2024 PDC25” are discussed.

As part of the SMPAG exercise held this year, the ESA NEO Coordination Centre (NEOCC) contributed in assessing potential impact scenarios for the simulated asteroid 2024 PDC25. By using all the available data at epoch 1 publicly realized in July, we used our Aegis system (1) to compute the orbit and the impact probability (IP) of 2024 PDC25 for the next 100 years. We found an IP of 1.6% in April 2024, with the nominal impact location over South Africa, and an impact corridor that extends from the South Pacific to the Arctic Sea passing through Africa, Western Asia, and Eastern Europe.
We later focused on predicting the IP evolution in the following months, and for that we generated synthetic observations using JPL’s Horizons system. The NEOCC observers team provided us with the necessary observational constraints. These synthetic data points enabled us to track how the asteroid's projected trajectory and impact probability shifted over time, ultimately confirming a 100% impact certainty as early as October 2025. In parallel, our team produced detailed keyholes map to better understand potential long-term perturbations and prepared comprehensive skyprints to aid observation efforts, providing critical insights for planetary defense strategies.
Our work provided robust orbital determinations and impact probabilities that were crucial to the decision-making process during this exercise. The synergy between risk assessment and observation teams enabled a seamless integration of data, yielding accurate predictions and highlighting the importance of coordinated international efforts in planetary defense.

(1) Fenucci, M., et al.: “The Aegis orbit determination and impact monitoring system and services of the ESA NEOCC web portal”, Celestial Mechanics and Dynamical Astronomy, (2024) 136:58

In planetary defense scenarios, there is often a limited amount of information about the properties of the object during the early phases. Statistical inference methods which leverage prior knowledge about the population of Near Earth Asteroids have successfully been utilized in PDC and IAWN exercises to augment the available measurements about the specific hypothetical impactor. The physical properties inferred by combining prior knowledge and available measurements have been used to assess the risk due to impact. In this paper we will examine how the details of the prior knowledge used in the statistical inference of physical properties effects the outcome of scenario risk assessments.

Keywords: asteroid, impact risk, modeling uncertainty

Determining the potential damage and risk from an asteroid impact involves many sources of uncertainty. Limited observational data leads to uncertainties in the asteroid properties, orbital uncertainties affect the potential impact location, and the entry and damage models all have some inherent modeling uncertainty. When each of these sources of uncertainty are combined, they can result in wide ranges for damage and risk estimates. As more information is gained about the object from additional observations or reconnaissance missions, uncertainties in asteroid properties and impact location are expected to reduce. A focus is therefore often placed on getting as much information as possible about a potential impactor. Modeling parameters, however, will remain uncertain. Therefore, from a risk perspective the question should be, what information refinements add meaningful value to making the best available decisions.

The compounding effects of uncertainty on hazard and risk calculations are highlighted by the range of results in the PDC25 impact exercise scenario. Even with help from JWST to constrain the size and type in the Epoch 1 assessment, asteroid property uncertainties lead to mass and energy ranges spanning multiple orders of magnitude. The Epoch 1 risk swath cuts through multiple regions including all of Africa, the Mediterranean, and Eastern Europe when accounting for orbital uncertainties. Together with modeling uncertainties, this leads to potential ground damage sizes ranging from zero or near zero up to 250 km and affected population estimates up to millions of people.

In this study, we use results from the Asteroid Threat Assessment Project (ATAP) Probabilistic Asteroid Impact Risk (PAIR) assessment to investigate which properties and parameters are most valuable to refine from a risk perspective for the PDC25 impact exercise scenario. We evaluate how different levels of precision in the inputs affect the model output precision along the swath, highlighting the variations in risk uncertainty reductions. Specifically, we will compare model output uncertainties assuming several different refinements (e.g. JWST, reconnaissance missions, etc.) and assess how our risk knowledge is affected by these additional sources of information. These results aim to start a conversation about what information makes the most difference from a risk perspective in determining when and how to act. Understanding the limits of what is most useful to evaluating potential damage and risk in this hypothetical scenario frees up additional resources to focus on factors that improve estimates in other areas, which may be vital in a real scenario where limited resources should be used most efficiently.

A hypothetical asteroid-impact scenario (http://neo.jpl.nasa.gov/pdc25/) will be used as the basis for discussion and analyses during the PDC 2025 table-top exercise. The asteroid is “discovered” on June 5, 2024, and is classified as a potentially hazardous asteroid with a diameter initially estimated between 90-160 meters with a median size of 125 meters and a full-size range of 50-280 meters. The large size uncertainty is due to uncertainties in both albedo and absolute-magnitude values. Based on the range of possible Earth impact velocities of 2024 PDC25 in 2041 and its estimated size and taxonomy, the energy released at impact is estimated to be most likely in the range 5 - 70 Mt, but possibly as large as 720 Mt. The expected damage of the impacts could be on the regional scale, likely extending as far as 110-200 kilometers from the impact location. The impact risk-corridor wraps more than halfway around the globe, cutting through Eastern Europe, the Mediterranean Sea, through central Africa to the Cape of Good Hope, across the South Atlantic to the Antarctic coast near the Antarctic Peninsula, and then into the South Pacific. Therefore, we focused our numerical simulation efforts on reflecting water, land, and ice portions of the impact corridor. Firstly, water impacts at a few locations at the Barents Sea, Mediterranean Sea, and South Atlantic & South Pacific oceans are simulated. Because most of the potentially affected South Africa’s False Bay region is heavily populated, we have conducted several high-resolution water-wave heights along the coastline under different conditions of the asteroid diameter & impact location uncertainties to assess flooding hazards and consequences. Secondly, for land impact and consequences, we numerically characterized the crater formation at impact locations given different geological conditions for different countries along the risk-corridor. Thirdly, we simulated numerically the impact of the asteroid on ice along West Antarctica to access the ice-sheet fracturing, melting and their consequences on global ocean circulation. Lastly, we simulated the airburst of the asteroid on two South Africain regions Stellenbosch & Cape Gate to assess the airburst pressure damage as function of airburst height and size of the asteroid. The impact of the asteroid with land, water and ice is simulated using the hydrocode GEODYN, creating a wave source for the Boussinesq-based water-wave-propagation code, WWP which has been used to predict the consequences of previous PDC & FEMA hypothetical exercises. For the ground motions propagation, the ground-impact source is coupled to the elastodynamic WPP code which has been used extensively by DOE. Airburst simulations have been conducted using solely by GEODYN. Impact of the asteroid on the global ocean circulations are being simulated using a new HPC exascale code called xGOC, not publicly released. We supplement the results at several stages with movies of asteroid impacts on different crustal emplacements using different asteroid impact velocities and angles.
Lawrence Livermore National Laboratory is operated by Lawrence Livermore National Security, LLC, for the U.S. Department of Energy, National Nuclear Security Administration under Contract DE-AC52- 07NA27344.

Keywords: Asteroid Threat Exercise, Earth Impact Effects, Impact Monitoring
Abstract
If the mitigation efforts do not succeed to alter the trajectory of 2024 PDC25, the
asteroid will impact near Cape Town, South Africa, depositing 250 megatons of energy
and creating a crater of about 3 km in diameter. If this happens it would be of obvious
interest to observe this impact in as much detail as possible.
It is proposed to populate the impact area with suitable sensors and probes, ranging
from drones in various altitudes in the atmosphere to the surface and below.
The expected phenomena include electromagnetic interactions with the atmosphere
and with the target material; pressure waves and acoustics in the air and on the
ground; events in the plasma and in the fireball, observable with suitable
spectrometers. Seismometer data can be combined with data from CTBTO. High
precision GNSS data, using differential GPS, could also be useful. Detailed satellite
monitoring, including using radar and radio signal monitoring instrumentation, would
also be of benefit. After an impact, an effort to reach the impact site to study the
distribution of rock types and take a variety of samples, and also to monitor the
temperature development of the crater fill rock, would be advantageous.
The goal of this presentation is to develop a strategy for these observations in terms
of requirements, capabilities, feasibility, and data sampling and storage. Suggestions
will be made as to the type of equipment, transmission frequencies and bandwidth.

The data can be collected in a suitable data base and combined with data obtained
from satellites and other remote sensing platforms. In this manner a full digital model
of the impact event can be constructed.

The Hera mission, which is part of the Space Safety Program of the European Space Agency (ESA), was launched on 7 October 2024 from Cape Canaveral with a Falcon 9 rocket. By the time of abstract submission it successfully completed most of its near-earth commissioning activities.

Hera will perform a rendezvous with Didymos in the fall of 2026 and investigate it over 6 months. With NASA’s DART mission, Hera will offer the first fully documented asteroid deflection test. DART successfully impacted Dimorphos, the 150 meter-sized moon of Didymos, on 26 September 2022 at approximately 6.1 km/s. The DART impact resulted in a decrease of 33 minutes from the original 11 hours 55 minutes orbital period of Dimorphos around Didymos. However, many questions remain, and although Hera returns to the system already visited by DART, the properties of the system will have changed in a way that may surprise us. It is clear that the Dimorphos that we know from DART’s images before impact will be very different when Hera sees it, reflecting how the DART impact modified it. Thanks to the great efforts of the DART team, the surface properties of the hemisphere of Dimorphos that was imaged before impact are well known, and it will be extremely interesting to see how those properties were changed by the impact. Among the questions that Hera will answer, the most important ones are: (1) What is the mass of Dimorphos, telling us momentum transfer efficiency of the DART impact? (2) What are the internal properties of Dimorphos, largely influencing the interpretation of the outcome of the DART impact? (3) What is the final state of Dimorphos, i.e., what is the size of the crater left by the DART impact or was Dimorphos globally or in large parts reshaped by the impact? (4) What is the rotational state of Dimorphos? Did the impact cause it to tumble?

The Hera mission will provide answers to these important questions that will lead to an unbiased interpretation of the outcome of the DART impact, and the possibility to fully validate numerical impact models aimed at reproducing the impact. With its mother spacecraft, which carries five instruments including a thermal infrared imager contributed by JAXA, and its two cubesats, Juventas, devoted to geophysics and Milani, devoted to mineralogy and dust analysis, Hera will investigate Didymos’ and Dimorphos’ state after the DART impact in great detail and provide measurements that have never been obtained for an asteroid so far. In particular, thanks to the low-frequency radar JuRa onboard the Juventas Cubesat, the first measurements of subsurface and internal properties of an asteroid will be achieved. Moreover, Hera will also perform the first landing of a Cubesat on a body as small as Dimorphos, offering an opportunity to measure the surface mechanical response of an asteroid in a very low gravity environment. Thanks to its detailed characterization of the binary system, Hera will answer key questions regarding the formation of small asteroid binaries and the geophysics of small bodies.

Our knowledge of the internal structure of asteroids relies entirely on inferences from remote sensing observations of the surface and theoretical modeling. Is the body a monolithic piece of rock or a rubble-pile, and how high is the porosity? What is the typical size distribution of the constituent blocks? Are these blocks homogeneous or heterogeneous? Direct measurements of an asteroid’s deep interior structure are needed to better understand asteroid accretion and their dynamic evolution. The characterization of the asteroids’ internal structure is crucial for science, planetary defense and exploration.

In orbit Radars sounding is the most mature instruments capable of achieving the objective of characterizing the internal structure and heterogeneity, for the benefit of science as well as for planetary defense or exploration.

JuRa
This is the goal of JuRa, the Juventas radar, onboard the ESA HERA mission. JuRa is a monostatic radar, BPSK coded at 60MHz carrier frequency and 20MHz bandwidth, inherited from CONSERT/Rosetta. HERA was launched last October to deeply investigate the Didymos binary system and especially its moonlet Dimorphos, five years after the DART/NASA impact. On HERA, the Juventas 6U CubeSat is carrying the Juventas Radar (JuRa).

JuRa maps the backscatter coefficient (sigma zero - σ0) of the surface and of the subsurface, which quantifies the returned power per surface or volume unit. It is related to the degree of heterogeneity at the scale of the wavelength and to the dielectric contrast of heterogeneities, giving access to both, the sub-meter texture of the constituent material and larger scale structures.
The main objective of JuRA is to characterize the asteroid interior, to identify internal geological structure such as layers, voids and sub-aggregates, to bring out the aggregate structure and to characterize its constituent blocks in terms of size distribution from submetric to global scale. The second objective is to estimate the average permittivity and to monitor its spatial variation in order to retrieve information on its composition and porosity.
The Multipass processing will allow us to build a 3D tomographic image of the interior at different scales from submeter to global.

Radar to Apophis
Knowledge of Apophis’ internal structure is crucial to better understand its accretion and dynamical evolution, to improve our ability to study its stability conditions and to model its response to the gravitational constraints induced by Earth close approach. The multi
A Radar to Apophis, RA, is under approbation for RAMSES/ESA mission to probe Asteroid 99942 Apophis in 2029, This radar is close to a carbon copy from JuRa with minor evolution and optimization for accommodation on a new CubeSat and to benefits from the JuRa lessons learned.
A modified version of JuRa able to operate in both monostatic and bistatic modes between two orbiting CubeSats is also under investigation for the “Mission to Apophis” understudy by JPL/Caltech inhering of the DROID studies. The bistatic radar mode will firstly measure the signal in transmission, allowing us to achieve a direct measurement of the dielectric permittivity, which is related to composition and microporosity. the bistatic mode will then allow a complete 3D tomography benefiting from angular decorrelation of the size effect and permittivity contrast in the return power.

In this talk will present the instruments, their status, performances and goals as well as the science objectives in the context of the different targets.

Acknowledgments
Hera is the ESA contribution to the AIDA collaboration. Juventas and JuRa are developed under ESA contract supported by national agencies.
JuRa is built by Emtronix (LU), UGA/IPAG (FR), TU Dresden (DE), Astronika (PL) and FZ (CZ). Juventas is built by Gomspace (LU).
This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 870377 (project NEO-MAPP).

On April 13, 2029, (99942) Apophis with a diameter of about 340 meters will approach Earth’s surface at about 31,000 km. Significant tidal torques will be exerted on Apophis, with possible alterations of its rotation state and internal structure, measurable seismic waves and real-time surface disturbances. This very close Earth flyby presents an unprecedented planetary defense and science opportunity.

A rendezvous space mission to Apophis will allow transforming our understanding of the response of small asteroids to external forces and of the internal structure of potentially dangerous asteroids.

The European Space Agency mission called RAMSES (Rapid Apophis Mission for SpacE Safety) is based on an adaptation of the Hera spacecraft [1], to fit to the updated mission profile, while minimizing any new developments given the short timescale until launch in April/May 2028 for a direct 10-months transfer and a rendezvous in February 2029. RAMSES embarks two visible cameras, Opportunity payloads and two 6U-XL CubeSats with payloads belonging to the Opportunity category. Opportunity payloads further contribute to the planetary defense objectives and increase the overall scientific return of the mission, without blocking the launch date in case of delay. Preliminary opportunity payloads are based on maximisation of the Hera mission heritage: a JAXA-led Thermal Infra-Red Imager based on the one onboard Hera, another camera,possibly provided by a partner agency (e.g., refly of the multispectral imager, MAPCAM, from OSIRIS-APEX), a laser altimeter, a refly of the JuRa low-frequency radar and of the GRASS gravimeter onboard the Hera Juventas Cubesat, a refly of the dust detector and analyzer VISTA onboard the Hera Milani Cubesat, a compact seismometer (geophone), and other potential payloads. The final payload suite will be fixed in mid-2025.

At Apophis arrival, high-resolution imaging at decreasing distances from Apophis down to 1 km at 10cm/pixel will be achieved. During the close Earth encounter, the spacecraft will hover at 5 km, a safe distance where the full asteroid figure will be visible by the Asteroid Framing Cameras. A similar set of characterizations will be performed after Earth encounter, to identify the expected changes in physical properties of the asteroid. The two CubeSats will be released in proximity of Apophis before the close encounter and will operate independently, using RAMSES as relay. One CubeSat will land on Apophis before the close encounter, carrying a seismometer and a gravimeter. The other CubeSat will embark the low-frequency radar to probe the subsurface properties of the asteroid and their possible modifications resulting from the Earth close approach.

In addition, in the late phase NASA OSIRIS-APEX [2] will have reached Apophis so additional combined synergetic observations might be planned, emphasizing the international cooperation that is at the heart of planetary defense. RAMSES is the second ESA mission to characterize a near-Earth asteroid, which is part of the planetary defense roadmap while offering a great science return. Its development started during a pre-funding phase including an ongoing Preliminary Design Review (PDR) at the time of writing this abstract and a Critical Design Review (CDR) around the time of its formal approval at ESA Council at Ministerial
Level in 2025.

References
[1] P. Michel, M. Kueppers, A. C. Bagatin, B. Carry, S. Charnoz, J. de Leon, A. Fitzsimmons, P. Gordo, S. F. Green, A. Herique, M. Juzi,
O. Karatekin, T. Kohout, M. Lazzarin, N. Murdoch, T. Okada, E. Palomba, P. Pravec, C. Snodgrass, P. Tortora, K. Tsiganis, S. Ulamec, J.-B. Vincent, K. Wuennemann, Y. Zhang, S. D. Raducan, E. Dotto, N. Chabot, A. F. Cheng, A. Rivkin, O. Barnouin, C. Ernst, A. Stickle, D. C. Richardson, C. Thomas, M. Arakawa, H. Miyamoto, A. Nakamura, S. Sugita, M. Yoshikawa, P. Abell, E. Asphaug, R.-L. Ballouz, W. F. Bottke, D. S. Lauretta, K. J. Walsh, P. Martino, I. Carnelli, The ESA Hera Mission: Detailed Characterization of the DART Impact Outcome and of the Binary Asteroid (65803) Didymos, PSJ 3 (2022) 160.
[2] D. N. DellaGiustina, M. C. Nolan, A. T. Polit, M. C. Moreau, D. R. Golish, A. A. Simon, C. D. Adam, P. G. Antreasian, R.-L. Ballouz, O. S. Barnouin, K. J. Becker, C. A. Bennett, R. P. Binzel, B. J. Bos, R. Burns, N. Castro, S. R. Chesley, P. R. Christensen, M. K. Crombie, M. G. Daly, R. T. Daly, H. L. Enos, D. Farnocchia, S. Freund Kasper, R. Garcia, K. M. Getzandanner, S. D. Guzewich, C. W. Haberle, T. Haltigin, V. E. Hamilton, K. Harshman, N. Hatten, K. M. Hughes, E. R. Jawin, H. H. Kaplan, D. S. Lauretta, J. M. Leonard, A. H. Levine, A. J. Liounis, C. W. May, L. C. Mayorga, L. Nguyen, L. C. Quick, D. C. Reuter, E. Rivera-Valentin, B. Rizk, H. L. Roper, A. J. Ryan, B. Sutter, M. M. Westermann, D. R. Wibben, B. G. Williams, K. Williams, C. W. V. Wolner, OSIRIS-APEX: An OSIRIS-REx Extended Mission to Asteroid Apophis, PSJ 4 (2023) 198.

The OSIRIS-APEX spacecraft will characterize asteroid (99942) Apophis over 18 months in 2029 and 2030 [1-3]. The mission is split into phases designed to address specific scientific objectives [3]. Because of the long period and non-principal axis rotation of Apophis, APEX will observe at regular intervals every few hours as it moves through multiple observing geometries to build up coverage while Apophis rotates and precesses. The initial observations are designed to be agnostic to Apophis’ physical state, so that later observations can be adjusted based on what is discovered upon arrival. The OSIRIS-APEX team is currently refining the concept of operations and mission phase designs.

Imaging with OSIRIS-APEX instruments will begin in late March 2029, with acquisition of Apophis as a disk-integrated point source no later than April 2, 2029. The spacecraft will make a close approach to Earth on April 13, 2029, only 1 hour after the Apophis-Earth encounter. During the approach phase, we will acquire observations to develop a global shape model, determine Apophis’ rotation state after the Earth encounter, and search for natural satellites and particles.

The proximity operations phases begin in June 2029 with global mapping to obtain datasets at the lighting conditions and viewing geometries necessary to build global topographic maps for precise navigation and to improve knowledge of the rotation state. We will also collect imagery for a global basemap and measure the asteroid’s mass.

Detailed mapping of Apophis begins in August 2029 with insertion into a terminator orbit at ~1 km altitude. This phase involves collecting scanning lidar topographic data and initiating the Yarkovsky measurement. In the subsequent detailed mapping phase, the spacecraft traverses a wide range of phase angles to collect global photometric and spectral datasets from 5–7.5 km. The final detailed mapping phase uses a resonant terminator orbit to acquire higher-resolution imagery for a global basemap and thermal observations of the night side of Apophis.

In April 2030, we transition into regional mapping of Apophis from altitudes of 1 km down to several hundred meters. One of the regional mapping locations will be used for the Spacecraft Thruster Investigation of Regolith (STIR) sortie, during which the spacecraft descends to a few meters above the target site, and thruster plumes from the back-away maneuver excavate and expose subsurface material. In November 2030, high-resolution observations will be collected during one final regional mapping pass to document the surface changes and newly exposed subsurface.

[1] DellaGiustina, D. N. et al. (2023) Planet. Sci. J. 4, 198. doi:10.3847/PSJ/acf75e
[2] Nolan, M.C. et al. (this meeting).
[3] Roberts, J. H. et al. (this meeting).

The planetary defense is an important activity for humankind. JAXA has been involved in this activity for long time, and recently Planetary Defense Team has been established and started to work.
The first thing to do for the planetary defense is to discover celestial bodies that will collide with the Earth and to estimate their orbits accurately. We carry out observations of Near-Earth objects (NEO) as well as space debris at Bisei Spaceguard Center. We also developed a method for discovering fast-moving objects that are approaching the Earth, and successfully discovered approximately 10 small NEOs using a small telescope with a diameter of about 20 cm.
If a celestial body that will collide with the Earth is discovered, we will try to avoid the collision. In order to do so, we need to know the physical properties of NEOs. We investigated physical properties of two NEOs, (25143) Itokawa and (162173) Ryugu by Hayabusa and Hayabusa 2 missions. Hayabusa2 mission has been extended after the Earth return, and it will explore two more NEOs, (98943) Torifune and 1998 KY26. Hayabusa2 will flyby Torifune in July 2026, and arrive at 1998 KY26 in July 2031. Torifune flyby has a planetary defense purpose in engineering as well. We will try to make Hayabusa2 approach very closely to Torifune in the relative velocity of 5km/s. If we can perform the spacecraft navigation very precisely, we can have ability to collide spacecraft to a small asteroid. The exploration of 1998 KY26 is also very important for the planetary defense because it is very tiny asteroid (size is estimated as 30m). Such kind of asteroids have the Earth collision probability of once in 100 or 200 years. In addition, we are collaborating with ESA's Hera mission, which will explore Dimorphos, the satellite of (65803) Dydimos, that NASA's DART collided with and successfully changed its orbit. We provided Infrared camera (TIRI) to Hera. We are also working for ESA's RAMSES mission to explore asteroid Apophis, which will approach the Earth in 2029.
Other activities related to the planetary defense in JAXA include orbit analysis of NEOs, participation in international conferences, and outreach activities. Collisions of celestial bodies that cause major damage will happen once every few decades, and such disasters can be predictable and avoidable if we can find celestial bodies colliding with the Earth in advance. We will continue our activities that will contribute to the planetary defense.

Hayabusa2# is an extended mission of Hayabusa2, which will spend another decade conducting various scientific and engineering investigations highlighted by a flyby at Asteroid (98943) Torifune in 2026 and a rendezvous with Asteroid 1998 KY26 in 2031. Our space flight operations have continuously performed cruise science investigations of exoplanets, comets, and zodiacal light. Recently, the mission has also weighed our efforts more to plan flyby operation sequences at its target, (98943) Torifune, formerly 2001 CC21. Planned to be in July 2026, the flyby observation is an excellent opportunity to detail this asteroid geologically. Unlike a rendezvous observation, however, the flyby at an encounter speed of 5.3 km/s challenges detailed scientific observations. Regardless of the spacecraft's tight system constraints, maximizing scientific return is essential to address our science objectives.

Hayabusa2 #'s science objective for the Torifune flyby is to determine the asteroid's taxonomy, shape, and morphological features as much as possible under extremely limited fast-flyby conditions to constrain its contribution to material transfer and demonstrate critical Planetary Defense technologies. The measurement requirements to achieve this objective specify the necessary performances of the onboard remote-sensing instruments: the Optical Navigation Camera Telescope (ONC-T), Thermal Infrared Imager (TIR), Near Infrared Spectrometer (NIRS3), and Laser Altimeter (LIDAR). Given highly tight constraints, while ONC-T and TIR will challenge their resolution limits, NIRS3 and LIDAR will attempt to detect at least one data sample.

The science operation planning divides science observation sequences into two phases. The first phase targets observations relatively far from Torifune 5 minutes before the closest approach (T-5 min to the CA). Because this phase actively controls the spacecraft via optical navigation, guidance, and control, science observations are expected to be limited and must meet zero conflicts with the planned system sequences using ONC-T for optical navigation. Limited scientific observation chances also challenge the simultaneous use of multiple remote-sensing instruments for science operations.

Conversely, the second phase can focus more on science investigations from T-5 min until the CA. This phase is planned to have more time for science observations. The primary discussion among the science team is about how to use the available time to maximize science return. The second phase also needs to determine the view geometry and CA timing for science observations based on Torifune's shape and rotational state. The mission's system team gave the science team flexibility regarding the timing and approach direction at the CA. We are currently identifying a sequential plan that can characterize the asteroid's geological and thermal conditions at most but can still satisfy the system constraints.

Considering all possible conditions, the Hayabusa2# team offers a holistic science observation plan for the Torifune flyby. This paper summarizes the current status of the mission's science operation planning.

To be able to provide advanced warning of future or imminent impacts of asteroids or comets, the first step is to observe the sky and discover these objects by means of dedicated NEO surveys. Most current and planned NEO surveys are ground-based and carried out in the visible wavelength range. However, this approach has some limitations, such as (1) weather dependency, (2) that only a portion of the night sky is visible from any given location on Earth, (3) NEOs are difficult to detect at low galactic latitudes and (4) that visible-light surveys can only determine the motion and apparent magnitude of an object, but its physical properties (such as size) can only be inferred indirectly and therefore require additional observations for characterisation.

A space-based mission working in the thermal infrared (IR) and placed at the first Sun-Earth Lagrange point (L1) would overcome most of these issues: in fact, by regularly scanning an area not easily accessible from ground or other space-based NEO surveys, it will be capable of detecting and characterising new NEOs and - in the worst case of an imminent impactor - serve as an early warning system.

To fill the above-mentioned gap, ESA is studying a NEO Mission in the Infra-Red, NEOMIR hereafter. NEOMIR’s main objective is to detect objects of at least 35 m (i.e. similar to the Tunguska event) coming from the region inside the Earth’s orbit and with sufficient warning time to prepare appropriate mitigation measures. This is achieved by (1) pointing closer to the Sun and at all Ecliptic latitudes and (2) shortening exposure times and increasing the cadence of revisit, ensuring that faster and therefore closer NEOs are not missed. The thermal infrared data will allow both initial orbit assessment and direct size measurements.

We will present the mission and spacecraft design, the status of the project as well as initial results on expected detection capabilities. We will focus on its ability to detect possible Earth impactors, determine their orbit and impact location.

99942 Apophis was a target of intense optical and radar observing campaigns during the 2012--2013 apparition when the asteroid approached Earth within 0.097 au. Radar observations were obtained on 19 days between 2012 December 21 to 2013 March 16 Brozovic et al. (2018) and lightcurve observations were obtained on 49 days between December 23 and April 15 Pravec et al. (2014). Brozovic et al. (2018) and Pravec et al. (2014) estimated the shape and spin state based on separate studies of radar and optical data. The Brozovic et al. (2018) model was estimated from radar data with coarse resolution relative to the size of Apophis, incomplete rotation coverage, and weak signal-to-noise ratios, and did not include lightcurves in the modeling, so we knew that the model could be improved and was not unique. Here we combine the 2012--2013 radar and lightcurve data for the first time and report new estimates of the shape and spin state.
Based on the lightcurves, Pravec et al (2014) reported that Apophis is a slow rotator in a tumbling spin state. The long axis precesses around the angular momentum vector with a period of 30.56 h and the asteroid oscillates (i.e., rolls) about the long axis with a period of about 11 days. Pravec et al. reported a convex shape model with axis ratios of $a/c=1.64\pm0.9$ and $b/c=1.14^{+0.04}_{-0.08}$. The spin state derived from the lightcurves reproduces the orientations and shapes of the delay-Doppler echoes (Brozovic et al. 2018). The radar data showed evidence of bifurcation that does not appear in the convex shape model estimated from lightcurves.
In the new analysis discussed here we fit a contact binary shape to the 2012--2013 lightcurve and radar data, and we find that the data are not very selective with respect to various degrees of bifurcation. Minor adjustments to the Pravec et al. (2014) spin state and moderate increases in the elongation of the 3D radar model from Brozovic et al. (2018) significantly improve the fits to the combined radar and lightcurve data. We will summarize the shape constraints that we can derive at this point and discuss plans for propagating the spin state from 2013 to the radar and optical data obtained in 2021. The next opportunities to observe Apophis with lightcurves will be in early 2028 and again from late 2028-April 2029. The next opportunity for radar observations begins about one month prior to the closest approach in April, 2029.

Asteroid Apophis rotates in an excited rotation state described by two periods, rotation and precession, with the values of 263 h and 27.38 h, respectively. Together with other spin parameters and a convex shape model, these periods were derived by [1] from photometric observations carried out in 2012/13. Radar observations are consistent with the spin state derived from light curves, and the derived shape model is nonconvex [2].

We carried out photometric observations of Apophis with the Danish 1.5m telescope at La Silla, ESO, between November 2020 and May 2021 to use them with old photometric data to determine its precise spin state. Due to the long time interval of eight years between observations, the rotation parameters could be determined precisely, which would enable us to (i) predict its orientation before and during the close approach in 2029 and (ii) estimate the change of its spin state caused by the Earth’s gravitation torque during the encounter.

However, when applying the light curve inversion method [3], we realized that the spin state cannot be determined uniquely. Different spin parameters provided about the same quality of the fit to the data. Fortunately, because of the same 8-year separation between 2012/13, 2020/21, and 2029, all acceptable spin solutions that fit the data from 2012/13 and 2020/21 phase together again in 2029, which means we can predict the attitude of Apophis during its close approach with the Earth on 13 April 2029. However, our simulations show that the way Earth’s gravitation torque affects Apophis’ spin during the flyby is so sensitive to the precise orientation of Apophis (affected by the YORP effect and
model uncertainties) that the spin state after the approach is uncertain.
Observations from 2027 and 2028 are crucial to uniquely determining Apophis’ spin state; photometry from 2029 will not be sufficient.

On April 13, 2029, asteroid (99942) Apophis will pass within 32,000 km of Earth, offering a unique opportunity to study how Earth’s tidal forces affect asteroids, particularly those with complex internal structures. This study investigates possible mass shifts and structural changes within Apophis during its close encounter, focusing on the implications of its bilobed shape, resembling a contact binary. To do this analysis we employ Contact Dynamics (CD) granular mechanics simulations using the LMGC90 software to model Apophis as a multi-body system. CD methods are well-suited for modeling the interaction between strong components of a micro-gravity rubble pile body, as it does not allow for interpenetration or distortion of the individual grains, as opposed to Soft Sphere Discrete Element Methods (SSDEM). Also, CD allows for the use of polyhedron bodies for the individual grains, allowing for shape effects and complex geometries naturally. In our study we focus on the neck region between the two lobes, which will be the point of maximum stress when Apophis has its close Earth approach. We survey a range of different morphologies for the main components of Apophis and interstitial boulders, using both spherical particles and polyhedral particles. Our simulations are focused on the 12-hour flyby period when all of the Earth interactions occur, exploring the effects of orientation, friction, and cohesion. Our preliminary results show that the spherical models exhibit larger mass shifts, with the internal cores able to shift up to 1° when Apophis’s long axis was offset from Earth, rather than directly aligned. The polyhedral models tend to exhibit smaller mass shifts, with relative angle changes between the two lobes at least an order of magnitude less. We also observed minor boulder displacements in the neck region, typically on the order of centimeters, with occasional displacements exceeding 1 meter. These results suggest that Apophis’s neck is sensitive to tidal forces and will experience surface shifts during the flyby. This study highlights the need for in-situ observations to confirm the surface and internal changes predicted during the Apophis flyby. It also provides specific target regions where observations should be concentrated.

The upcoming close encounter of asteroid 99942 Apophis with Earth in 2029 presents a once-in-7000-year opportunity to study the dynamics, bulk properties, and interior structure of a potential rubble-pile asteroid as it passes through Earth’s gravitational field. Numerical modeling—including via Discrete Element Methods (DEMs)—has helped to develop our understanding of the dynamics and physical outcomes of the tidal encounter between Apophis and Earth, including the expected change in the bulk shape and spin of the body, and predictions of potentially measurable surface and seismic outcomes due to the short period of natural tidal forcing. These models have helped to plan, orient, and design missions to Apophis to ensure that we can make the most of the natural experiment that the Apophis encounter provides.

We will present new and ongoing DEM models of the full Apophis-Earth close encounter, making use of recent developments in modeling realistic particle shapes with both a “glued-sphere” approach and a level-set DEM approach in the N-body gravity and soft-sphere DEM code PKDGRAV. The glued-sphere method provides simpler spherical gravity and collision detection calculations but requires smaller timesteps and stiffer constituent particles. The level-set method provides a more realistic shape representation at the cost of increased memory requirements and the loss of precise gravitational torques (as we do not calculate polyhedral gravity). Here, we compare the results and performance of both techniques.

Modeling with irregular particle shapes (rather than spheres) allows us to increase the macroporosity of the resultant rubble pile while also increasing the body’s shear strength. This occurs naturally when packing irregular shapes due to the void spaces created by interlocking grains, and the physical strength of those interlocked structures, which cannot be replicated by spheres alone. These methods allow us to create a high macroporosity regolith body—like those investigated in recent missions to rubble-pile asteroids Bennu, Ryugu, and Itokawa—that is also more resistant to reshaping or disaggregation than previous spheres-only models.

In our simulations, we model Apophis as a rubble pile constructed of irregular particles in the several-meters size range, with different interior structure profiles, including contact-binary, large single-core, and rubble throughout. We present the influence of these different interior structure profiles and constituent grain shapes in the plausible range of close-approach distances, and compare the deformation, spin change, and induced seismicity measurements with previously published/presented spheres-only simulation results and analyses.

The close approach of 99942 Apophis, on April 13th, 2029, will offer a wide portfolio of scientific opportunities to study a near-Earth asteroids physical and orbital properties and how these are affected by close approaches with planets. Yet, although its probability of impact with our planet was definitively ruled out in March ’21, the extraordinary event of a ~ 375 m diameter object and an estimated mass of ~ 20 million tons passing inside the Geostationary ring, with a nominal distance of ~ 38000 km from Earth, will pose relevant dynamical challenges and potential risks to Earth's satellite infrastructures, and the unique occasion to study how satellites are affected by bulky asteroids very close approaches.
This paper aims at modelling and analysing the gravitational perturbation introduced by Apophis’ passage on Earth satellites, and to estimate the delta-V budget required to counteract Apophis' gravitational pull and maintain satellite operational orbit. In absence of station-keeping maneuvers, the maximum deviation a satellite's orbit can experience due to Apophis' influence is firstly estimated, examining how it will affect their orbital elements depending on the satellite's orbital characteristics, both for LEO and GEO satellites. An effective station keeping strategy is then implemented, which allows an estimation of the total delta-V budget required to counteract the gravitational pull of the asteroid, validated through simulations on well-known mission analysis high precision software. By understanding the specific effects of Apophis' close approach, this research aims to provide valuable insights into the potential risks and challenges posed by near-Earth object close approaches to satellite operations. These results can be used to develop strategies for mitigating the impact of such events and ensuring the continued reliable operation of satellite systems.

Near-Earth asteroid (NEA) 99942 Apophis is interesting because it will make an exceptionally close approach of the Earth in 2029 at a geocentric distance of 38,000 km making it the closest known flyby by a large NEA. The International Asteroid Warning Network (IAWN) conducts campaigns to test the operational readiness of the global coalition of observers, modelers, and decision makers to assess a potential NEO impact hazard. In preparation for the 2029 close approach of Apophis, the IAWN is planning a two-phased campaign: a pre-encounter large-aperture and spacecraft phase in 2027 and 2028 that will be focused on NEO science, and a 2029 close approach phase focused on planetary defense with citizen science participants. Due to Apophis' relatively faint visual magnitude and short observing windows, the 2027 and 2028 opportunities will concentrate on refining its rotation state and gathering additional visible spectra. The IAWN will coordinate the large-aperture and space telescopes observing efforts. Observers will self-organize but will be advocated by the IAWN when they apply for telescope time. Scientific results from these efforts will be published independently by respective PIs with coordination from the IAWN. The 2029 close approach will be the primary focus for more direct IAWN efforts. Some of the campaign themes we are exploring include: a traditional IAWN campaign treating Apophis as a newly-discovered NEA, which would be similar to our 2021 Apophis campaign; enabling participation of small telescopes (<1 meter aperture) like those aligned with the proposed International Year of Planetary Defense; better coordination with Planetary Defense Conference exercise if there is one planned around Apophis in 2029 and integrating results from spacecraft rendezvous missions planned at or near the Apophis closest approach.

The flyby of Apophis in 2029 offers an opportunity to prove out rapid planetary defense mission concepts from Earth orbit. We will present a mission concept developed at Lawrence Livermore National Laboratory that achieves key planetary defense objectives of characterizing Apophis with two small satellites placed in flyby orbits from GTO. The spacecraft will be equipped with 25cm aperture optical telescopes capable of high resolution imagery during the Apophis flyby. These observations will deliver key information on the surface structure, rotation state, and changes that occur during tidal interactions with the Earth over the period where the tidal forces are largest. The data will be highly complementary to OSIRIS-Apex.

After the consecutive Apophis encounters, the spacecraft will be useful planetary defense assets at a time when the Vera Rubin Observatory and NEO Surveyor are detecting a large number of potentially hazardous asteroids for the first time. These asteroids will be submitted to the Minor Planet Center as all new discoveries are, but the faint magnitude limits of the Rubin Observatory and the complicated observing conditions from the ground for NEO Surveyor detections will pose challenges for following up new discoveries.

This paper offers an analysis of the performance of two 25 cm optical telescopes in the proposed orbits of our mission concept. These orbits are accessible by GTO rideshare to flyby Apophis. Residual fuel will allow for maneuvers to regularize the orbits and prepare for a dedicated residual mission of NEO tracking for orbit refinement and characterization. The two satellites will allow for simultaneous binocular observations with a long baseline. This will enable rapid orbit refinement and characterization with broad-band photometry in the visible band.

The Near Earth Object (NEO) 99942 Apophis provides a unique opportunity for an operational Planetary Defense (PD) scenario. Discovered in 2004, Apophis was initially identified as a highly hazardous asteroid that could impact the Earth. Dedicated tracking campaigns have allowed scientists to eliminate any risk of impact during the April 13, 2029 flyby; however, Apophis will pass within less than 32,000 km (below Geostationary Orbit) from the Earth’s surface. Although the OSIRIS-APEX mission will rendezvous with Apophis post-flyby, the ability to perform a flyby before the Earth encounter provides an opportunity to characterize asteroid properties prior to influence of Earth’s gravity, where the effects become measurable inside 30 Earth radii.

This investigation proposes the novel use of cislunar orbits to design a potential Apophis flyby mission prior to Earth close approach. Due to the proximity of the Apophis-Earth flyby, lunar resonant and Lagrange point orbits provide an excellent location for staging and subsequently enable a low-propellant asteroid encounter opportunity outside the prescribed 30 Earth radii. Both Earth-Moon and Sun-Earth Lagrange point staging orbits were considered. Additionally, in order to alleviate the burden associated with launching a spacecraft, this investigation considered launching as a secondary payload compatible with any primary spacecraft en route to the Moon (e.g. NASA CLPS, etc.), constructing the required transfer orbits to reach the desired cislunar staging orbit. The time spent in the staging orbit can be tailored to enable maximum flexibility with launch opportunities and, in this analysis, staging times between 1-6 months prior to spacecraft encounter with Apophis are investigated.

The example mission concept of operations explored here for an Earth-Moon L3 staging orbit includes the following:
• Launch to the Moon as a ride-share and adjust the lunar flyby conditions to enable a 2-4 month low-energy ballistic lunar transfer.
• Insert into the appropriate Earth-Moon L3 staging orbit, with the number of revolutions in the staging orbit dictated by launch date.
• Refine phasing on the staging orbit to setup the Apophis close-approach encounter.

The upcoming Apophis flyby provides an opportunity to examine the physical characteristics of an asteroid prior to an Earth close approach below 30 Earth radii. For Apophis, the observed parameters prior to the Earth close approach can be compared to the post-Earth parameters calculated by the upcoming OSIRIS-APEX mission. The mission concepts detailed in this investigation demonstrate the feasibility of a low-cost and flexible solution that leverages novel cislunar staging orbits to enable future NEO encounters.

The close flyby of asteroid (99942) Apophis on April 13, 2029 presents a unique
opportunity to achieve scientific and planetary defense goals. A multi-spacecraft
mission concept to exploit this opportunity has been developed in a collaboration
between Caltech, JPL and CNES. The Caltech-led mission is being pursued as a
privately funded venture with commercial partners. Its architecture employs a high
delta-V Mothership and two 12U CubeSats that would rendezvous with Apophis prior
to Earth closest approach and escort it through the encounter. Its measurements can
determine: the body’s shape and density; the size, distribution, and arrangement of
blocks and voids in the interior; surface movements or reshaping during the Earth
flyby; as well as spin state changes. Its goals are to understand the interior structure
of a (presumed) rubble pile asteroid and implications for its formation, evolution and
response to deflection, and to understand how close planetary encounters affect
asteroids. The Caltech mission would provide unique high fidelity in situ data to
complement and enhance Earth-based optical and radar observations of Apophis, as
well as data from NASA’s OSIRIS-APEX mission. Low-frequency (≤60 MHz) bistatic
radar observations are performed to probe Apophis’s interior, revealing the
distribution of monolithic objects and voids within. These data would complement
low-frequency monostatic radar data from ESA’s RAMSES mission should it fly a
radar. The Mothership would carry the CubeSats to Apophis, achieve the
rendezvous cruise trajectory, perform high resolution imaging, and act as a Direct-to-
Earth node for the constellation. A narrow-angle multi-band camera on the
Mothership performs imaging for shape, morphology and geology. After deployment,
the CubeSats insert themselves into coordinated low orbits to perform monostatic
and bistatic radar observations to probe internal structure. Radar data products
include 3D volumetric backscatter via monostatic/bistatic tomographic SAR, and
average dielectric constant along interior bistatic ray paths to assess internal
heterogeneity. Inter-Spacecraft Link S-band transponders on all spacecraft perform
intra-constellation data transfer, synchronize the CubeSat clocks for accurate bistatic
radar measurements, and aid in recovering Apophis’s gravity field. The mission is
currently in Phase A, with partnerships and funding to be finalized early next year.
1
Acknowledgement: A portion of this work was carried out at the Jet Propulsion
Laboratory, California Institute of Technology, under a contract with the National
Aeronautics and Space Administration (80NM0018D0004).

An understanding of both surface and interior properties of potentially hazardous objects enables accurate characterizations of their geological and geophysical conditions for planetary defense purposes (e.g., risk assessment and impact mitigation), in addition to their formation and evolution mechanisms relevant to planetary science investigations. Asteroid 99942 Apophis will fly by Earth within a distance of ~6 Earth radii on April 13, 2029. This event will be a rare opportunity to observe the reaction of a small, suspected rubble-pile body to planetary tidal forces. Caltech is leading a first-of-its-kind mission that would rendezvous with Apophis before its Earth Closest Approach (ECA) and escort it through the approach. The mission will aim to improve our understanding of the interior structure, surface conditions, and potential dust environment of Apophis, which may be representative of rubble-pile asteroids. The mission would consist of a spacecraft constellation comprised of a mothership and two CubeSats equipped with radar to characterize possible surface and internal changes throughout the ECA.

Here, we compile and summarize Apophis modeling and data, focusing on knowns, unknowns, current science knowledge gaps, and how Caltech’s mission would fill those gaps. We discuss current knowledge around the surface dynamics and interior structure of rubble-pile asteroids, implications for asteroid formation and evolution, predicted responses to the Earth encounter via numerical modeling, and how these predictions flow down to mission requirements (e.g. defining imaging resolution based on the scale of predicted resurfacing). We also outline how Caltech’s mission fits within the landscape of other Apophis missions such as OSIRIS-APEX and RAMSES, and how its unique bistatic radar dataset complements the data returned by other missions.

The $\sim$325-meter diameter Potentially Hazardous Asteroid (PHA) designated 99942 Apophis 2004 MN$_{\text{4}}$ will make a historic close approach of Earth on April 13th, 2029, passing within $\sim$31,634 km of Earth’s surface, $\sim$4,152 km closer than our geosynchronous satellites. This is an extraordinarily unique opportunity for collecting data on a several hundred-meter size asteroid while it experiences the effects of close proximity to Earth’s gravitational field. Current asteroid population models suggest that this is a 1 in 7500 years event. Apophis’s Earth close encounter therefore provides a rare opportunity to observe planetary encounter effects on an asteroid.

Our Terrapin Engineered Rideshare Probe for Rapid-response asteroid Apophis Profiling, Tracking, Observing, and Reconnaissance (TERP-RAPTOR) is an Earth-orbiting mission concept in which a 12U CubeSat built by University of Maryland students would perform a flyby of Apophis, collecting data to address science questions regarding the asteroid's collisional and dynamical evolution, its surface and structural characteristics, and the effects of close proximity to Earth's gravitational field. This mission also supports planetary defense objectives by advancing our understanding of Apophis-sized objects and their potential Earth impact risks.

The mission launches as a rideshare into an Apophis-intercepting orbit, an example of which is shown in Figure 1. We present several design reference mission cases, including an orbit potentially reachable from a typical Geosynchronous Orbit Transfer (GTO) rideshare launch, a high-inclination sub-geosynchronous altitude orbit with lower flyby speed and more benign radiation environment, and a retrograde orbit scenario minimizing flyby speed relative to Apophis but requiring advanced future launch rideshare systems, such as Blue Origin’s Blue Ring.

After launch and separation, TERP-RAPTOR performs on-orbit commissioning, loiters, and then maneuvers to fly by Apophis at its perigee. Data is collected by two cameras: a high-resolution RGB imager for wide-field analysis of asteroid size, shape, spectral weathering signatures, and crater distribution; and a multi-spectral imager with customizable bands (up to near-infrared) to detect fine-scale surface changes. TERP-RAPTOR will also carry an antenna instrument provided by the High-frequency Active Auroral Research Program (HAARP) and collect HAARP's bi-static radar signals reflected by Apophis, in collaboration with the Owens Valley Radio Observatory. Those data help characterize portions of Apophis's interior. Image data and HAARP data will be stored onboard and down-linked to ground stations.

The spacecraft may then perform extended missions. As the spacecraft nears the end of its operational lifetime, it will conduct End-of-Life operations adhering to NASA Procedural Requirements for Limiting Orbital Debris.

TERP-RAPTOR is an innovative design for a small, affordable University-built spacecraft capable of providing a higher ratio of scientific return to mission cost than any previous mission to an asteroid or comet. Apophis will be naked-eye visible in the night sky in parts of Europe and Africa, capturing the attention of everyone around the world. As people's eyes and imaginations gaze upwards, TERP-RAPTOR will be our eyes in space, alongside any other spacecraft that the nations of the world might dispatch to study this extraordinary natural event.

The physical properties of potentially hazardous small bodies are critical for planetary defense studies. The Sq-type asteroid (99942) Apophis, an Aten asteroid with an Earth-crossing orbit, will pass within ~32,000 km of Earth on Friday April 13, 2029. This close encounter could induce surface alterations of Apophis, such as landslides and mass wasting, due to gravitational interactions with Earth. NASA’s OSIRIS-APEX will visit Apophis a few weeks after the closest approach of the asteroid to the Earth to observe these potential surface changes after the Earth encounter and will stir up surface regolith using thrusters. ESA’s RAMSES will visit the asteroid starting from a few weeks before encounter to measure its initial properties and how they change during the closest approach (Michel et al., this conference). Other spacecraft may also participate in investigations of Apophis during its Earth encounter.

We here propose conducting low-energy multi-impact experiments on Apophis after its Earth encounter, using a payload onboard a spacecraft performing a rendezvous with Apophis, to further study its physical and material properties of Apophis, such as surface regolith cohesion, boulder strength, space weathering effects, and regional variations of these properties. The mechanism for launch of the projectiles on the payload can take advantage of technological heritage from ALE's human-made shooting star satellites (https://star-ale.com/en/technology/). As demonstrated by Hayabusa2’s small carry-on impactor experiment (Arakawa et al., 2020; Kadono et al., 2020), impact experiments are invaluable for studying the surface properties of small bodies. The proposed impacts (up to 10–20), with low kinetic energy (~50-100 J per projectile), are about 1/4-1/2 of that of JAXA’s Hayabusa2 sampler (Sawada et al., 2017; Thuillet et al., 2019; Tachibana et al., 2022) and are expected to make ~10-cm craters on regolith or chip off boulders. We also note that these low energy impacts will not alter the Apophis’s orbit.

The proposed impact experiments will provide us with additional opportunities for active/dynamic exploration of Apophis, complementing the effect of Earth’s tidal forces and OSIRIS-APEX’s thruster experiment. We believe that low-energy multi-impact experiments will provide unique scientific insights and enhance the overall value of all space missions to Apophis.

We define a mission concept to perform a cratering and deflection experiment at Apophis with an independent impactor spacecraft that leverages the formidable capabilities of OSIRIS-APEX as an observer. This is relevant to both planetary defense and science.

A 65kg spacecraft impacting Apophis at 7km/s will make a crater between 20-50m [1,2], and result in an excavation of 2-8m deep. This is deeper than previously explored in rubble piles and into the depths where studies have suggested increased strength at the asteroids Bennu and Ryugu [1,3]. For the estimated mass of Apophis the resulting Delta-V would be ~0.01mm/s. While incredibly small, it is ~2.5x larger than the formal 1-sigma tracking uncertainties for OSIRIS-REx at Bennu and OSIRIS-APEX at Apophis would be similarly capable [4]. While estimates exist for the response of rubble piles to cratering impacts of this magnitude, additional experiments, like this one, are needed for objects the size of Apophis, which has implications for planetary defense strategies.

Performing this experiment after OSIRIS-APEX achieves its primary science goals means that the mass and spin state of Apophis would be known, where a mass measurement to 1% accuracy is planned [5]. This will permit a very accurate measurement of the momentum transfer due to the cratering impact.

There are many technical pathways to achieve this mission [6]. Since OSIRIS-APEX would be employed for the measurement of the target mass, imparted Delta-V and cratering outcomes, the only required vehicle is an impactor that has sufficient combination of speed and mass to produce the required 0.01mm/s Delta-V. There are several low C3 (<5 km2/s2), ballistic transfer opportunities in 2029 and 2030 that impact Apophis after the OSIRIS-APEX science campaign. The relatively low-mass and low-launch energy means the mission can use a small-to-medium lift launch vehicle, keeping costs low.

Some of the possible pathways include resonant trajectories that permit concept of operations that include a trial run, or a two-spacecraft concept with impacts on consecutive years. Similarly, other scenarios could utilize the JANUS spacecraft, where one spacecraft impacts while the other provides flyby reconnaissance of the event.

One important note is that this kinetic impact and cratering experiment would not change the risk of an Apophis impact. The targeted Delta-V and the time of impact are bracketed by the values studied in the hazard assessment of the Apophis Specific Action Team Report, where impacts with 100x this Delta-V were included at similar epochs [7]. They found that such perturbations to Apophis’s orbit were “assuredly safe” and there was no chance of impact out to the 2116 Earth encounter. We can thus see this experiment as an extraordinary opportunity to contribute to our understanding of the response of potentially hazardous asteroids to a deflection test with no risk, following the NASA DART-ESA Hera deflection test and leveraging the knowledge gained by missions visiting Apophis in the previous months, like ESA RAMSES and NASA OSIRIS-APEX.

References:

[1] M. Arakawa, et al., Science, vol. 368, pp. 67-71, 2020.
[2] E. B. Bierhaus, et al., Icarus, vol. 406, 2023.
[3] Daly, R. T., et al., Icarus, vol. 384, Art. no. 115058, 2022.
[4] D. Farnocchia, et al., Icarus, vol. 369, 2021.
[5] D. N. DellaGiustina, et al., The Planetary Science Journal, 2023.
[6] Klein, V., Walsh K. J., and Kayser E. IAC 2024 Paper #87838. 2024. https://iafastro.directory/iac/paper/id/87838/summary/
[7] J. L. Dotson, in Apophis T-6: Knowledge Opportunities for the Science of Planetary Defense, Leiden, 2023.

The Pan-STARRS-1 telescope in Maui, Hawaii performed a multi-purpose survey of the of the sky north of -30° declination from 2010 to 2014. From 2014 onwards, the main focus of Pan-STARRS has been a survey of the sky for Near-Earth Objects (NEOs), funded by the NASA Planetary Defense Program. With the addition of the second telescope, Pan-STARRS has become one of the leading surveys for Near-Earth Objects. In 2024, Pan-STARRS achieved its highest number of NEO discoveries, and even higher discovery rates are expected in the future.

A major strength of the Pan-STARRS NEO survey has been discovery of larger NEOs. Pan-STARRS has consistently discovered more than half of all NEOs with diameter >140 meters each year. Another strength of Pan-STARRS is excellent astrometry, which assists in candidate recovery, helps produce better orbits, and can reveal curvature in tracklets that is a signature that an object is nearby. Pan-STARRS discovers more than half of its NEOs south of the celestial equator. As the Rubin Observatory begins surveying the southern sky, some complementarity with the Pan-STARRS survey is expected, with the telescopes likely providing follow up for each other’s discoveries.

The main characteristics of the Pan-STARRS survey will be summarized, and some of the recent improvements will be explained. Some of the systematics that arise from the survey will be described. Discovery highlights include the first interstellar object, `Oumuamua (also an NEO). A new detection-based discovery technique will be explained. This is expected to enable discovery of fainter NEOs, further increasing the discovery rate, and will also help in the discovery of potential impactors (such as the near-miss object 2019 OK) by helping discovery of slow moving objects that may be headed directly towards Earth. It is likely that this technique will also produce discoveries of more distant comets (that are moving very slowly) and other outer solar system objects. Follow up of fainter NEO candidates will continue to be challenging. Self-follow up is already important, and is expected to become more important.

The Catalina Sky Survey is a world leader in the discovery and astrometric follow-up of near-Earth objects (NEOs) As such, we continuously update and refine our algorithms to improve our operations. Here, we present three recent enhancements to the Catalina Sky Survey operations model in both discovery survey and targeted follow-up.

First, we have recently, in collaboration with the ATLAS group [1], developed a machine learning routine that classifies transient detections. Currently, three classes have been developed: stellar, streak, and diffraction spike. We have trained a convolutional neural network using data sets containing thousands of examples of each class from our 703 Schmidt survey telescope. Examples from the training sets are shown in Figure 1. Transient sources are classified using the 30x30 matrix of pixels surrounding them. These classifications are then used to weigh potential discovery tracklets made up of four transients. Tracklets consisting of probable diffraction spikes are demoted while those consisting of probable streaks or stellar objects are promoted. Preliminary results show a 5% increase in known NEO tracklets scoring above our review threshold. We plan on expanding this functionality to our G96 survey telescope once our training data set for it is complete.

Second, we have developed a “second chance” reprocessing routine for failed follow-up attempts. Working with the developer of Tycho Tracker synthetic tracking software, we have incorporated their software into our normal operations. When a follow-up target is not found by our normal moving object detection pipeline, we can now re-stack the images using a range of motion vectors. This technique can recover objects that had significant star interference or were tracked at different rates than the true sky motion of the target. An example of the routine’s effectiveness can be seen in Figure 2, where our normal stacking on the object’s rate of motion is seen in Figure 2a, and the power of synthetic tracking to reduce the interference from background stars is seen in Figure 2b. It can be triggered as soon as a follow-up attempt has been found unsuccessful and completed within minutes. This has directly reduced the amount of telescope time used to re-observe targets and has saved over 70 follow-up targets since becoming operational in early 2024.

Finally, to probe deeper into our nightly candidate tracklets, we have developed a citizen science project on the Zooniverse platform called ”The Daily Minor Planet”. This project takes 22 additional candidate tracklets from our nightly G96 survey and presents them to volunteers for review. If a candidate receives sufficient votes by the volunteers as being real, it is reviewed by our follow-up observers and can be reported to the Minor Planet Center. This has doubled the number of candidates reviewed from our survey data, resulting in three confirmed NEO discoveries, and has enabled thousands of volunteers from around the world to participate directly in planetary defense.

References
[1] A. C. Rabeendran, L. Denneau, A Two-stage Deep Learning Detection Classifier for the ATLAS Asteroid Survey, Publications
of the Astronomical Society of the Pacific 133 (2021).

The ATLAS telescopes have largely operated using a traditional discovery mode in which data from each telescope are processed separately and NEOS are discovered from a series of four "quad" observations from one telescope. Since they operate independently, sky coverage (and therefore NEO discovery) are subject to losses from poor weather; for example, a quad of observations can be spoiled by a single bad observation with clouds, or an entire night of ineffective observations can be executed because of thin clouds over an entire part of the sky for the entire night. The data processing for the ATLAS telescopes has also operated independently, with separate processing streams for each telescope -- the system cannot easily combine the data from multiple telescopes to discover objects. For example, a faint object might appear only three times in a quad, not enough to confirm as a detected object, but another telescope might also have three faint observations, so in theory the combined detections can be confirmed by testing the large number of potential linkages.

With the expansion of ATLAS to a five-observatory system with geographic and weather diversity, we have embarked on a two-pronged strategy to enhance the discovery capability of ATLAS network of telescopes. In this talk, we present ADIOS (the ATLAS Dynamic Inter-Observatory Scheduler), a program that can simultaneously schedule all operating ATLAS telescopes for maximum NEO discovery in the face of weather and other observational losses. ADIOS employs an NEO population model and awareness of local sky conditions to decide where to observe at any given instant to maximize the NEO discovery rate. ADIOS can avoid patches of sky where discovery is unlikely, and ADIOS can divert another ATLAS observatory to complete a quad spoiled by weather or twilight.

ADIOS is complemented by another software component called PUMA (Position Using Motion and Acceleration), a performant orbit fitter that can evaluate thousands of short-arc (~1-2 day) linkages per second on a single CPU. We can use PUMA to test linkages of faint three-detection tracklets across all ATLAS observatories, effectively improving the sensitivity of the ATLAS survey. We present results of PUMA cross-observatory linkages with the ATLAS telescopes and a pilot effort to cross-link ATLAS with the Catalina Sky Survey 703 telescope. This effort dovetails with similar projects in the field such as the Juric et al. 2024 HelioLinC linking service B612's ADAM precovery service that incorporate data across observatories.

To detect unknown and potentially dangerous asteroids, ESA’s Planetary Defence Office prepares the operation of a network of so called FLYEYE telescopes.
ESA’s Test Bed Telescope (TBT) project is laying the groundwork for the efficient operation of these telescopes. The project consists of two identical telescopes: one located at ESA’s ground station in Cebreros, West of Madrid in Spain, and one at the European Southern Observatory (ESO) La Silla observatory in the Atacama desert in northern Chile. The TBT network is augmented by the 80-cm-Schmidt Telescope at the CAHA observatory in in the Sierra de Filabres, in the province of Almería, Spain.

The presentation gives an overview of the survey activities conducted with these telescopes and how they lead to the discovery of unknown objects. It is described how the observation are planned and implemented and how the resulting data are processed automatically.

2022 EB5, 2023 CX1 and 2024 BX1: these are the three recent imminent impactor discoveries from the Piszkesteto Mountain Station of the Konkoly Observatory. They make up about a quarter of all known such events since 2008 and one may ask what makes our survey sensitive to these little impactors. In this talk we describe our recently upgraded survey instrumentation, outline the observational strategy and the methodology with which we perform real-time analysis of the observations. We highlight the importance of the strong feedback between analysis and on-going data collection that maximizes the value of immediate follow-up. Finally, we discuss plans for moving forward to increase the sensitivity and the temporal and spatial coverage of our survey.

We simulated the operations of the Vera C. Rubin Observatory in observing 5,000 virtual impacting asteroids over a range of size bins, whose orbits were chosen to impact Earth over a period of 50 years. We used the Sorcha package to simulate the observations of these impactors for the planned 10-year Legacy Survey of Space and Time. We performed running orbit fits for the state vector and covariance to these observations as a function of time, then carried out Monte-Carlo simulations to calculate impact probabilities, which start small and evolve towards 1 as more observations are taken and as the impact date approaches. We tabulate the distribution of impact probabilities as a function of time before impact across all of the simulated impactors.

In particular, although these asteroids were constructed to hit Earth, the impact probability for any one impactor takes some time to rise to a significant level due to the fitted orbit’s uncertainty. We quantify the number of observations and time it takes for the impact probability to reach the early warning and mission planning threshold of 1%, as defined by the Space Mission Planning Advisory Group (SMPAG), if the Rubin observatory were the only telescope contributing observations. We can then characterize the warning time of the asteroid impact as the interval between when the impact probability reaches this threshold and the predicted impact date.

We investigate how this warning time varies with asteroid size and orbital characteristics. These findings are critical for preparedness efforts, as they highlight the importance of early and accurate detection to maximize warning time. Finally, we evaluate the implications of these findings for planetary defense, underscoring the importance of robust survey operations and follow-up observations to ensure that impact probabilities are calculated early enough to allow for required mitigation efforts. By quantifying the timeline of rising probabilities, we provide actionable insights into how long we will have to prepare for potential impacts in the Rubin era.

The airburst event over Chelyabinsk, Russia in 2013 caused over 1,400 injuries and $30 million in property damage. This object was not tracked until it entered the Earth’s atmosphere, too late for any disaster response, partly because of its small (~20 meter-diameter) size, but also because it approached from interior to Earth’s orbit, obscured by the Sun’s brightness. The Chelyabinsk superbolide thus highlights an undersampled group of potentially hazardous asteroids: low-solar-elongation Aten-family (primarily) bodies whose orbits are largely interior to the Earth, and thus difficult to observe.

These “Sunward NEOs” (SNEOs) are high-risk due to the difficulty of confirming discoveries with subsequent same-night or multi-night observations, and their short impact warning times. It is thus critical to find and characterize SNEOs and predict their trajectories so that their long-term orbits can be tracked more carefully.

Studies in the last decade indicate that initial twilight observations (during the 10–45 min when the Sun has just set below the horizon in the evening or just before it rises above the horizon in the morning) on survey telescopes like ZTF and DECam have led to discoveries, and dynamical characterizations of potentially hazardous SNEOs. The Vera Rubin Observatory has published plans for a “low-solar-elongation twilight microsurvey,” which will capitalize on its wide field of view and large aperture to resolve even fainter objects and get better signal-to-noise—which could be critical for twilight observations, where the sky is not completely dark. Following initial identification from Rubin, other twilight-capable telescopes can perform observations to characterize orbits, compositions, and rotations, thus reducing threats.

Thus, for my winning planetary defense proposal for the B612 Foundation’s inaugural, 2024 Schweickart Prize for Planetary Defense, I proposed the SUnward NEO Surveillance and Early Twilight detection (SUNSET) community and observatory collaboration. SUNSET will, in the short term, advocate for and facilitate starting the Rubin twilight survey for SNEO detection in Year 1 of operations, and organize a follow-up characterization network of ground-based observatories–utilizing twilight time, when science observations are generally not taking place. As a first step in organizing follow-up, we aim to develop tools to prioritize objects for follow-up observations and provide relevant observing details, so that any observer with a twilight-capable telescope can be a part of SUNSET.

We hope to engage the broader community by incorporating amateur- and small-observatory follow-up observations and linking them to the data from primary discovery telescopes with novel orbit-recovery tools like THOR, from the B612 Foundation. THOR can derive orbits from disparate data sets or images from different nights in a way that de-emphasizes the observer’s relative position and relaxes the need to observe repeatedly in subsequent nights and form “tracklets,” meaning that anyone willing to do follow-up observations can help contribute to data sets and help SUNSET make Earth safer!

Keywords: Near-Earth asteroids, NEOCP, MPC, impactors

The Minor Planet Center (MPC) serves as the single worldwide location for tracking and cataloging asteroids, natural irregular satellites of the major planets, and comets, making it central to planetary defense efforts. Operated at the Smithsonian Astrophysical Observatory in Cambridge, MA, under the auspices of the International Astronomical Union and funded by NASA’s Planetary Defense Coordination Office, the MPC provides publicly accessible data, orbital elements, and products through web-hosted tools (APIs) and files. Additionally, a live PostgreSQL database, updated in real-time during submission processing, allows for data replication and improves accessibility.

A key service is the NEO Confirmation Page (NEOCP), which offers observations and ephemerides for newly discovered, fast-moving, or otherwise unusual objects requiring immediate confirmation. This tool is crucial for rapid response, especially when identifying potential Earth impactors with only hours of lead time.
We will provide an update on current MPC services, with an emphasis on NEOCP performance in scenarios involving newly identified impactors. We will also outline our ongoing efforts to adapt to future survey demands, such as those anticipated from the Vera Rubin Observatory (VRO/LSST) and the NEO Surveyor mission.

Key improvement include:

• Enhancing processing pipelines for greater efficiency and scalability.
• Optimizing usability and accessibility of observation and orbit database tables.
• Strengthening the validation of data products.
• Upgrading communication and redesigning the MPC website for a more user-friendly experience.

Over the past two decades, nearly all Near-Earth Objects (NEOs) have been discovered mostly by dedicated surveys through the use of preselected candidates posted to the Minor Planet Center's (MPC) Near-Earth Object Confirmation Page (NEOCP). Rapid follow-up observations from the astronomical community typically allow for the designation of new NEOs within a few days. As of today, more than 37,000 NEOs have been discovered, with an average discovery rate of approximately 3,000 per year since 2020. Candidate preselection is based on the NEO digest2 score [1,2], with only short-arc tracklets achieving a score of NEO digest2 $>$ 65 being posted to NEOCP. Previous studies [1] have shown that NEOs generally achieve digest2 scores close to 100, while other orbital classes exhibit significantly lower scores. For instance, typical main-belt objects have scores near zero. The frequency of NEOs sharply drops as a function of decreasing digest2 NEO score on NEOCP. Annually, about 6,000 candidates are posted to NEOCP, with roughly 10\% remaining unconfirmed due to a lack of follow-up observations [3]. Among confirmed candidates, two-thirds are designated as NEOs, while the remainder are predominantly main-belt objects.

We present a detailed analysis of 13 distinct digest2 orbital categories , evaluated in two modes—'raw' and 'noid'—for NEOCP candidates since 2019. Our aim is to reduce the proportion of non-NEOs on NEOCP. By leveraging all derived digest2 parameters, rather than relying solely on the NEO digest2 score, we demonstrate the potential to eliminate up to 20\% of non-NEO candidates.

Furthermore, we applied four machine learning (ML) methods that we already studied on simulated short-arc LSST tracklets [4]: Gradient Boosting Machine (GBM), Random Forest (RF) classifier, Stochastic Gradient Descent (SGD) classifier, and Neural Network (NN)—to the derived digest2 scores for NEOCP candidates from 2019 onward. Using NEOCP candidates observed between 2019 and 2023 as the training dataset, and 2024 candidates as the validation dataset, we achieved NEO prediction accuracies of 91\%-92\%, with model performance differing by at most one percentage point.

We propose that the implementation of derived digest2 filters and ML methods could significantly reduce the number of non-NEO candidates on NEOCP. This would provide more efficient use of follow-up observation time and decrease the fraction of unconfirmed NEOCP candidates, most of which are likely NEOs and therefore increase the number of NEO discoveries.

References:
[1] S. Keys, P. Veres, M. J. Payne, M. J. Holman, R. Jedicke, G. V. Williams, T. Spahr, D. J. Asher, C. Hergenrother, The digest2
neo classification code, Publications of the Astronomical Society of the Pacific 131 (2019) 1–22.
[2] P. Veres, R. Cloete, R.Weryk, A. Loeb, M. J. Payne, Improvement of Digest2 NEO Classification Code-utilizing the Astrometry
Data Exchange Standard, 135 (2023) 104505.
[3] P. Veres, M. J. Payne, M. J. Holman, D. Farnocchia, G. V. Williams, S. Keys, I. Boardman, Unconfirmed Near-Earth Objects,
156 (2018) 5.
[4] R. Cloete, P. Veres, A. Loeb, Machine learning methods for automated interstellar object classification with LSST, 691 (2024)
A338.
2

The motion of an asteroid over its hour long ''tracklet'' (a short sequence of observations) is often used to estimate the likelihood of it being interesting [1] -- that is, not exhibiting the motion typical of main belt asteroids. This is done by computing a numerical score, 0-100, which must be >65 for the object to be considered a Near-Earth Object (NEO) candidate.

However, there are limitations to this method, and it has been shown [2] that some NEOs do not meet this minimum score when they are first visible. As well, while objects closer to the Earth are likely to have larger score, they will often exhibit curvature -- non-linear motion which also causes their Great Circle Residuals (GCR) to be large. Both of these facts were indeed the case for 2020 SO = P116rK2, an object hidden in plain sight which was thought to be interesting, but was soon realised [3] to be the upper stage Centaur from the 1966 Surveyor 2 spacecraft launch.

While our daily search of linking observations in the recent Isolated Tracklet File (ITF; a rich repository of all orphan tracklets) to discover NEOs is on-going, it requires a minimum of three tracklets observed on different nights. In this current study, we instead focus on increasing the NEO discovery rate by identifying curvature within single tracklets. We have developed new tracklet linking software which does this by fitting acceleration terms with their uncertainties. While we still make use of the recent ITF, we have also begun to process "chip" images from Pan-STARRS which are more sensitive than the "diff" images created from an image-differencing algorithm used in the regular pipeline.

Our search for potential candidates does require immediate follow-up effort, but we have expertise from the two major sky surveys as well as the Minor Planet Center. We will present a summary of our search to date, along with a discussion of whether other surveys would benefit from adopting a similar search.

[1] S. Keys, P. Veres, M. J. Payne, M. J. Holman, R. Jedicke, G. V. Williams, T. Spahr, D. J. Asher, C. Hergenrother, The digest2 NEO Classification Code, 131 (2019) 064501

[2] R. Weryk, R. Wainscoat, P. Veres, NEOs in the Isolated Tracklet File, in: 7th IAA Planetary Defense Conference, p. 32.

[3] Deletion of 2020 SO, Minor Planet Electronic Circulars 2021-D62 (2021).

A common question from the public is: How many dangerous asteroids could potentially hit the Earth? Our response usually starts by mentioning that the number is size-dependent, because while there are numerous small asteroids, they pose less threat to life on Earth.

We have agreed to use two limits: 1km objects for global catastrophes and 140m objects for regional events.

In the last 25 years, I have counted at least 12 different estimates of the population number for various size limits [1,2,3,4,5,6,7,8,9,10,11,12]. Specifically, the estimates for the number of NEAs larger than 1km range widely, from fewer than 800 to over 1,200 (including error bars). A critical aspect in all models is the relationship between absolute magnitude and diameter, which depends on the (generally unknown) albedo.

There is a lower constraint for this number: the NEAs already discovered that are larger than 1km. However, this brings us back to the albedo problem. Are all these estimates consistent with this constraint?

The number of NEAs larger than 1km is a critical issue for the public, decision-makers, and scientists. Therefore, we should strive to reach a consensus based on the evidence.

Although I have not been involved in any of the previous works, I have closely followed the topic and am in a very favorable position to make a critical revision of all the estimates and propose a figure for this relevant number.

The aim of my presentation is to come up with a realistic number based on the models and observational constraints.

References:
1. D’Abramo, G. et al., 2001. A simple probabilistic model to estimate the population of near-Earth asteroids. Icarus 153, 214–217.
2. Bottke, W.F., et al., 2002. Debiased orbital and absolute magnitude distribution of the near-earth objects. Icarus 156, 399–433.
3. Stuart, J.S., Binzel, R.P., 2004. Bias-corrected population, size distribution, and impact hazard for the near-Earth objects. Icarus 170, 295–311.
4. Mainzer, A., et al., 2011. NEOWISE observations of near-earth objects: Preliminary results. Astrophys. J. 743:156
5. Harris, A.W., D’Abramo, G., 2015. The population of near-Earth asteroids. Icarus 257, 302–312.
6. Granvik, M., et al., 2018. Debiased orbit and absolute-magnitude distributions for near-Earth objects. Icarus 312, 181–207.
7. Morbidelli, A., et al., 2020. Debiased albedo distribution for near earth objects. Icarus 340, 113631
8. Harris, A.W., Chodas, P.W., 2021. The population of near-earth asteroids revisited and updated. Icarus 365, 114452.
9. Harris, A.W., Chodas, P.W., 2023. Update of NEA population and survey completion. In: ACM Conference in Flagstaff, #2519.
10. Nesvorný, D., et al., 2023. NEOMOD: A new orbital distribution model for near-earth objects. Astron. J. 166:55.
11. Nesvorný, D., et al., 2024. NEOMOD 2: An updated model of near-earth objects from a decade of catalina sky survey observations. Icarus 411, 115922.
12. Nesvorný, D., et al., 2024. NEOMOD 3: The debiased size distribution of Near Earth Objects. Icarus 417, 116110.

Impact risk is normally quantified by summing the product of the probability of an event and some measure of its consequences over the set of all possible events. The probability factor is considered to be more objective and is based on the size frequency distribution of NEOs and an implicit assumption of randomness, which can be described as “stochastic catastrophism”. Impact frequency does change with time, however, and there have been episodes in the deep geological past when the flux has been much higher.

The hypothesis of “coherent catastrophism” suggests large variations on shorter timescales. It postulates the existence of a “Taurid resonant swarm” (TRS) of debris associated with Comet Encke that is stabilized by Jupiter and in a 7:2 resonance with it. The hypothetical cluster orbits in the broad Beta Taurid stream, which crosses Earth’s orbit twice a year at its nodes. Theoretical calculations by Asher and Clube [1] suggest that the last close approaches, within 1° absolute mean anomaly difference |$\Delta$M| were in November 1971 and June 1975 for its perihelion approach and departure, respectively. Circumstantial evidence (large daytime fireballs and seismic activity on the moon at the time of the 1975 crossing) are consistent with an increase in the flux of larger fragments. Rates and data for fireballs that correlated with the predicted 2015 return were recorded by Egal et al. [2]. Large uncertainties remain in the number of objects larger than meter-sized in the TRS, so its significance to risk remains poorly constrained and contentious. There is some evidence for a few objects large enough to be hazardous, associated with the 2015 swarm, but the population has not yet been shown to be statistically significant.

In 2019 and 2022, the predicted node crossings were close enough to attempt targeted surveys [3,4], with |$\Delta$M| of 5° and 17°, respectively, based on extrapolation of predicted swarm encounters [1]. Upcoming potential targeted survey opportunities will be 2025, 2026, and 2029 (|$\Delta$M| of 25°,18° and 23°, respectively). Targeted surveys provide the opportunity to put further constraints on the population of the hypothetical swarm as well as to determine potential future close passes or impacts if the swarm exists. The 7:2 resonance with Jupiter happens to come close to a 18:61 resonance with Earth, so the next set of 1° node crossings will be in 2032 and 2036, which would be years of increased impact probability. We also suggest that this possibility could form the basis for a semi-hypothetical tabletop exercise, based on the trajectory of the Tunguska object, which was in an orbit consistent with the Beta Taurid stream [5]

Most members of the planetary defense community are skeptical of coherent catastrophism due to misinformation, misunderstandings, and misinterpretations associated with the Younger Dryas impact hypothesis (YDIH) and its pseudoscientific corollary claims [6]. Nevertheless, the possibility of enhanced risk from an undiscovered population of small NEOs in the hypothetical TRS should not be dismissed unless comprehensive targeted surveys demonstrate that there is no significant population.

[1] Asher DJ, Clube SV. An extraterrestrial influence during the current glacial-interglacial. Quarterly Journal of the Royal Astronomical Society, Vol. 34: 4/DEC, P. 481-511, 1993. 1993 Dec;34:481-511.
[2] Egal A, et al. An observational synthesis of the Taurid meteor complex. Monthly Notices of the Royal Astronomical Society. 2022 May;512(2):2318-36.
[3] Clark DL, et al. The 2019 Taurid resonant swarm: prospects for ground detection of small NEOs. Monthly Notices of the Royal Astronomical Society: Letters. 2019 Jul;487(1):L35-9.
[4] Li J et al. Search of the Potentially Hazardous Asteroids in the Taurid Resonant Swarm. 2024, in press.
[5] Boslough M, et al. Analysis of the Tunguska Event as a Semi-Hypothetical Impact Scenario. 2023, American Geophysical Union Fall Meeting.
[6] Holliday VT, et al. Comprehensive refutation of the Younger Dryas Impact Hypothesis (YDIH). Earth-Science Reviews. 2023 Dec 1;247:104502.

NASA’s Near-Earth Object (NEO) Surveyor mission is an infrared observatory planned to launch no earlier than September 2027 that is designed to discover and characterize asteroids and comets. Its main objective is to identify those objects that are large enough (>140 m in effective spherical diameter) to cause severe regional damage from impact. The observatory will operate at the Sun-Earth L1 Lagrange point and conduct a survey to within 45° of the Sun in order to identify objects in the most Earth-like orbits[1]. During the length of the survey, NEO Surveyor is estimated to discover ~200,000 to 300,000 new objects (some as small as ~10 m) and thousands of comets. These discoveries will provide a more comprehensive understanding of the orbital and size frequency distribution of the NEO population, and also provide insights into the relative probability of an Earth impact during the next 100 years.

NEO Surveyor’s ability to observe regions close to the Sun increases the likelihood that it will detect objects in very Earth-like orbits. These objects tend to have the lowest minimum orbit intersection distances (MOIDs), and thus pose the greatest risk of Earth impact. NEOs on more Earth-like orbits are also more difficult to deflect, all else being equal. This attribute of NEO Surveyor’s operation is not only important for planetary defense considerations, but it also provides an opportunity to identify low-delta V spacecraft mission targets, which are of interest to the science, in situ resource utilization, and exploration communities.

The NEO Surveyor team has developed a model reference population of NEOs and other Solar System objects (e.g., mainbelt asteroids) in which to measure the effectiveness of the survey over its designed operational lifetime. This Reference Small Body Population Model (RSBPM) combines both a separate NEO model and a background object model to mimic the moving objects that the observatory will “see” during the operation of the survey. Based on the RSBPM, NEO Surveyor will be able to identify objects that are particularly accessible for both one way and round-trip rendezvous missions and span a range of NEO diameters. The majority of these low-delta V objects will likely be Atens, but will also include a significant number of Apollos.

In this paper, we will apply astrodynamics techniques to estimate the distribution of delta V and flight time requirements for both one-way and round-trip rendezvous missions to the population of NEOs that NEO Surveyor is expected to discover. We will utilize the algorithms for the Near-Earth Object Human Space Flight Accessible Targets Study (NHATS) [2], heuristics derived from the current NHATS data, and other techniques specific to one-way rendezvous trajectory calculations. The results will show us how the number of known attractive NEO mission targets may increase during NEO Surveyor’s survey operations.

References

[1] Mainzer, A. K., J. R. Masiero, P. A. Abell, J. M. Bauer, W. Bottke, B. J. Buratti, S. J. Carey, D. Cotto-Figueroa, R. M. Cutri, D. Dahlen, P. R. M. Eisenhardt, Y. R. Fernandez, R. Furfaro, T. Grav, T. L. Hoffman, M. S. Kelley, Y. Kim, J. D. Kirkpatrick, C. R. Lawler, E. Lilly, X. Liu, F. Marocco, K. A. Marsh, F. J. Masci, C. W. McMurtry, M. Pourrahmani, L. Reinhart, M. E. Ressler, A. Satpathy, C. A. Schambeau, S. Sonnett, T. B. Spahr, J. A. Surace, M. Vaquero, E. L. Wright, G. R. Zengilowski, and the NEO Surveyor Mission Team. “The Near-Earth Object Surveyor Mission”, The Planetary Science Journal, 4:224 (19pp), 2023 December.

[2] Barbee, B. W., Abell, P. A., Adamo, D. R., Alberding, C. M., Mazanek, D. D., Johnson, L. N., Yeomans, D. K., Chodas, P. W., Chamberlin, A. B., Friedensen, V. P., "The Near-Earth Object Human Space Flight Accessible Targets Study: An Ongoing Effort to Identify Near-Earth Asteroid Destinations for Human Explorers," 2013 IAA Planetary Defense Conference, Flagstaff, AZ, April 15-19, 2013

The United Nations established the International Asteroid Warning Network (IAWN), in 2013 to coordinate worldwide organizations involved in detection, tracking, and characterization of Near-Earth Objects (NEOs). In addition, developing well-defined communication plans and protocols to assist governments in the analysis of asteroid and comet impact consequences and in the planning of mitigation responses are also part of the IAWN's mandate. The IAWN conducts campaigns to test the operational readiness of a global coalition of observers, modelers, and decision makers to tackle a potential NEO impact hazard. Since 2017, the IAWN has conducted six exercises, four of which focused on planetary defense readiness and near-Earth asteroid (NEA) characterization, and two on improving the timing of astrometric observations that form the bedrock of NEO detection and tracking. Key findings from these campaigns include NEA characterization not being at the same operational readiness level as astrometry and hazard modeling; binary nature of the target NEA having very little effect on the impact risk on the ground; the need to reduce timing errors at some observatories as they can result in significant systematic errors that bias the trajectory estimate. Our timing campaigns showed us that astrometric timing errors are typically less than one second. However, there is an excess of negative values, i.e., the reported times for NEO positions were generally biased toward early values rather than being on time or ahead. We worked with individual observers to offer mitigation solutions to remedy the timing errors so that overall astrometric quality across the planetary defense community could be improved. The findings from each campaign, which have been published in peer-reviewed journals, led to the development of goals for subsequent exercises and helped improve the overall readiness of global planetary defense efforts.

Asteroid impacts have profoundly affected the evolution of life on Earth. Over the last 30-40 years, the field of planetary defense has identified the scope of the threat and is working to develop plans and technology to prevent asteroid impacts if possible and mitigate their effects as necessary. In particular, if an object were on a collision course with the Earth, early knowledge of key impactor characteristics is vital to inform the next planetary defense actions [1,2]. We further note the key importance of early size measurements by pointing to the objects that trigger SMPAG mission planning options: larger than 50 m diameter or H < 26 if a direct size measurement is not available, the latter condition necessary to account for 50-m, low-albedo NEOs. The vast majority of H < 26 objects will be much smaller than 50 m, but without the ability to measure their sizes they must be treated as though they are larger. Only two facilities have the capability to make the needed size measurements: Goldstone Planetary Radar, which requires a very close and lucky pass of the NEO in question, and JWST.

JWST has unique capabilities to provide early knowledge of the potential threat, in particular the Mid-Infrared Instrument (MIRI), which can make photometric and spectroscopic measurements from 5—28 µm, with the ability to distinguish > 50-m from < 50-m objects even if they are lurking in the middle of the asteroid belt. If an impact threat to Earth is found, it is likely that JWST/MIRI will be the best, fastest way to obtain a useful size measurement for such an object. This will be especially true during the upcoming period between first light for the Vera Rubin Observatory and the launch and operations of NEO Surveyor, when we can anticipate a flood of NEO discoveries of objects far beyond the reach of non-JWST mid-infrared platforms.

We will present the capabilities of JWST for early characterization of impactor sizes, including a study of how it would have performed in previous PDC and TTX impactor scenarios, and suggest how a program could be designed to trigger JWST observations in case of a credible impactor threat.

Observational capabilities are one of the key “pillars” of ESA’s Planetary Defence Office activities. This presentation will highlight recent developments, important results and key objectives of our follow-up efforts.

We will begin with an overview of the status and recent additions to our global network of fast-reacting facilities, which are playing a critical role in our follow-up of the many imminent impactors discovered over the past couple of years.

We will also discuss the follow-up work we perform nightly with other facilities under our control, in both hemispheres, focusing on how we optimise target selection between high-priority Risk List objects and under-observed candidates on the NEOCP.

As usual, a significant attention is placed on astrometric precision, including a particular care in determining proper error bars not just for astrometric measurements, but also for time and temporal biases. This allows us to fully exploit the capabilities of the ADES format, ensuring that this additional crucial information reaches the orbit computation systems.

Our wide range of facilities also allow us to address specialised observational challenges, ranging from coverage of low-elongation or very fast moving targets, to unusually faint follow-up, and to targeted astrometric observations designed to enable additional physical follow-up (e.g., ensuring the ephemeris accuracy necessary for physical characterization techniques or space-based detections).

Finally, in line with the collaborative spirit of NEO observations, we always ensure our team and facilities actively participate in all campaigns and initiatives sponsored by IAWN and SMPAG, essential players in the worldwide effort towards a truly global planetary defence strategy.

The Goldstone Solar System Radar on NASA’s 70 meter DSS-14 antenna is the world's most sensitive planetary radar. DSS-14 is equipped with a high-power (~450 kW) radar used for observations of near-Earth asteroids (NEAs), comets, and other solar system targets. Goldstone transmits at a frequency of 8560 MHz (3.5 cm), is fully steerable, routinely tracks down to a declination of -35 degrees, and can cover nearly 80% of the sky. Goldstone has real-time processing that displays delay-Doppler data within seconds of its acquisition. Radar observations provide substantial reduction in orbital uncertainties; for newly-discovered objects, Goldstone astrometry routinely reduces distance uncertainties by several orders of magnitude.

As of December 2024, 1124 NEAs (~3% of the NEA population) have been observed by radar, and of these, 509 have been observed at Goldstone. 196 NEAs have been detected at Goldstone since the end of operations at Arecibo in 2020. Of these, 151 (77%) were detected for the first time; 112 are "Potentially Hazardous Asteroids;" 131 have absolute magnitudes < 22, corresponding to diameters larger than ~140 meters; and 63 were targets-of-opportunity observed shortly after discovery.

52 NEAs have been detected at Goldstone in 2024, setting a new annual record. This represents a factor of ~1.5 increase relative to the average from 2012-2018 and a ~five-fold increase relative to 15 years ago. Detailed delay-Doppler imaging at a resolution of 4 meters/pixel is now occurring >10 times annually.

During 2021-2024, we observed 18 binary systems, 13 of which were Goldstone discoveries, and two triples. 75 binary and triple systems have been observed by radar, of which ~70% were discovered by radar. Since 2020, 13 contact binaries have been discovered at Goldstone. ALL near-Earth contact binaries have been discovered using radar.

42% (N = 471) of all NEAs observed by radar were also observed by the NEOWISE spacecraft, including dozens detected at Goldstone since 2020. These observations provide calibration of diameters estimated from NEOWISE observations and will help calibrate diameters from the upcoming NEO Surveyor mission.

Radar observations at Goldstone have become much more flexible: Priority for radar observations is now comparable to that for spacecraft missions and considerably more time has been scheduled. Transmit authorization is no longer required, allowing much greater flexibility for short-notice targets-of-opportunity utilizing time already scheduled. Some NEAs are observed within one day of when discovery is announced. The klystron amplifiers are dramatically more reliable. In 2024, new equipment was installed that allows Goldstone to conduct monostatic observations for objects as close as one lunar distance.

This talk will discuss observational trends, detailed images from recent observing campaigns, and discuss plans for the next five years.

Acknowledgments: Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (NASA). This material is based in part upon work supported by NASA under the Science Mission Directorate Research and Analysis Programs.

Many newly discovered near-Earth asteroids (NEAs) are small ($<$100 m), yet they still pose significant risks if they impact Earth. Therefore, continued research and observation are crucial for the small NEA population, where characterisation significantly lags behind discovery rates. Our program at the South African Astronomical Observatory (SAAO) utilises the robotic capabilities of the 1-meter Lesedi telescope, equipped with the Mookodi instrument (Erasmus et al. 2024), for rapid follow-up observations of newly detected NEAs.

Using automated scripts that continuously monitor NASA JPL’s Scout page, observations are scheduled in robotic mode, allowing data collection often within the same night of discovery—a crucial strategy given the rapid dimming of smaller NEAs as they move away from Earth. Since February 2023, we have observed approximately 230 NEAs, with an average absolute magnitude of 24.4, corresponding to a size of 30 to 80m depending on the albedo. Of all the asteroids we observed, 75% are under 100 meters in diameter, indicating that our strategy is successful in targeting the small NEA population, as is our goal for the program. Fifteen of the asteroids we followed up on have since been classified as potentially hazardous asteroids (PHAs).

This work presents findings based on multi-filter photometry and astrometric measurements collected in our program. Our astrometry has significantly contributed to the Minor Planet Center's orbital refinement for the submitted objects and collected g', r', i' photometry enables us to extract g' - r' and r' - i' colours, approximating spectral slope and aiding in determining the most likely taxonomic type (S, C, X, D, Q, and V-types for this project) of these NEAs based on the Bus-DeMeo Classification Scheme (DeMeo et al. 2009). Using the collected data, the compositional distribution of the small NEA population was determined and compared with previous studies.

Near-Earth Objects (NEOs), encompassing both asteroids and comets, are celestial bodies whose trajectories bring them into proximity with Earth, presenting both scientific opportunities and potential collision risks. A comprehensive investigation of their physical characteristics, dynamical behaviors, and orbital evolutions is paramount for planetary defense strategies and advancing astrophysical knowledge. This study leverages the 1.88m telescope at the National Research Institute of Astronomy and Geophysics (NRIAG) in Egypt to conduct targeted observational campaigns of NEOs.
Employing cutting-edge ground-based optical observation techniques, we achieved high-precision detection, tracking, and characterization of multiple NEOs. Advanced astrometric and photometric data reduction pipelines enabled the determination of orbital elements, size estimations, and compositional analyses. These methodologies underscore the strategic potential of regional facilities in contributing to the global network of NEO monitoring and research.
This work not only reinforces the critical role of localized observatories in the global observational infrastructure but also provides vital insights into the distribution, behavior, and resource potential of NEO populations. The findings significantly enhance the collective understanding of NEO dynamics, informing planetary defense initiatives and future resource exploitation endeavors.

The 4.3-m Lowell Discovery Telescope (LDT) is a highly efficient facility for the characterization of near-Earth objects. With multiple instruments simultaneously mounted, a combination of astrometric, photometric, and spectroscopic measurements are regularly made. Recent observations at LDT have focused on NEOs such as imminent impactors (2022 WJ1, 2024 XA1), mini-moons and lunar ejecta (2024 PT5), astrometric follow-up of objects experiencing non-gravitational orbital evolution (dark comets), and the completion of a spectro-photometric survey of nearly 200 objects to constrain the compositional distribution of small NEOs on Earth-like orbits. Highlights from these investigations will be presented in the context of how the demonstrated capabilities of the LDT are well matched to planetary defense efforts.

In November 2024, ESA’s Planetary Defence Office (PDO) organized the EU-ESA workshop on size determination of potentially hazardous near-Earth objects, held at ESOC in Germany [1]. The workshop explored how the minor body community can improve the size determination of NEOs. For an Earth impacting object, its size is the key factor in assessing potential ground damage [2]. Newly discovered objects lack detailed physical information and their size is poorly defined. This can lead to scenarios where an object may either be considered harmless, or require the evacuation of populated areas.

Key representatives from the photometric, thermal infrared, polarimetric, and stellar occultation communities were gathered. For each field, review talks were provided and methods to obtain the size or the albedo were presented and discussed

Asteroid size estimates from photometric observations are often poorly characterized due inconsistent data. Size is derived from the absolute HV magnitude, geometric albedo pV, and equivalent diameter [3], but determining HV requires phase curve modeling and low phase angle observations [4], which are often not available for NEOs. Even low phase angles can be observed, data remain sparse. To address this, surveys could target fields where known objects are at their lowest phase angle, optimizing observation sequences without reducing overall scientific returns. Additionally modern model like H, G1, G2, [5] should be utilized, as they can provide albedo information when sufficient data is available to constrain the G parameters.

In thermal infrared, the size is obtained directly by modeling the absolute thermal emission flux of the object, which depends on its temperature and size [6]. The community stresses that it is important to remember that thermal infrared measures the size and not the albedo [7]. The result of the discussion points to the need for a consolidated database aggregating all the thermal infrared observations obtained not only by all the space missions but also by the ground-based observatories.

The main advantage of polarimetric observations is their ability to determine an object’s albedo in dependantly of its size [8]. Unlike both the HV absolute magnitude, and thermal infrared observations, polarization is not affected by the object’s instantaneous cross-section on the sky. Polarimetry was recognized as the preferred technique to obtain albedos of NEOS. While HV estimates from photometric observations remains the simpliest method for determining the size of NEOs, efforts should focus on equipping large telescopes with more polarimeters. This would improve the albedo-polarimetry calibration, and allow polarimetric observations of recently discovered, potentially hazardous objects. Notably, while HV is still needed to estimate an object’s size, combining polarimetric and thermal observations may allow full characterization of an object without it.

Stellar occultation was also highlighted as a crucial technique to obtain direct size measurement of NEOs.

We would like to deeply thank all the participants of the workshop without whom this work would not have been possible. The list of participants, the presentations and the recordings of the talks can be found on the website of the event[1].

References
[1] EU-ESA workshop on size determination of potentially hazardous near-Earth objects, European Commission and ESA’s Planetary Defence Office, ESOC, Darmstadt, Germany, https://indico.esa.int/event/530/.

[2] D. L. Mathias, L. F. Wheeler, J. L. Dotson, A probabilistic asteroid impact risk model: assessment of sub-300 m impacts, Icarus 289 (2017) 106–119.

[3] E. Bowell, B. Hapke, D. Domingue, K. Lumme, J. Peltoniemi, A. W. Harris, Application of photometric models to asteroids, in: R. P. Binzel, T. Gehrels, M. S. Matthews (Eds.), Asteroids II, University of Arizona Press, 1989, pp. 524–556.

[4] M. Mahlke, B. Carry, L. Denneau, Asteroid phase curves from atlas dual-band photometry, Icarus 354 (2021) 114094.

[5] K. Muinonen, I. N. Belskaya, A. Cellino, M. Delbo, A.-C. Levasseur-Regourd, A. Penttila, E. F. Tedesco, A three-parameter magnitude phase function for asteroids, Icarus 209 (2010) 542–555.

[6] A. W. Harris, J. S. V. Lagerros, Asteroids in the thermal infrared, Asteroids III (2002) 205–218.

[7] J. R. Masiero, E. Wright, A. Mainzer, Uncertainties on asteroid albedos determined by thermal modeling, The Planetary Science Journal 2 (2021) 32.

[8] A. Cellino, S. Bagnulo, R. Gil-Hutton, P. Tanga, M. Canada-Assandri, E. Tedesco, On the calibration of the relation between geometric albedo and polarimetric properties for the asteroids, Monthly Notices of the Royal Astronomical Society 451 (2015) 3473–3488.

A critical component of planetary defense is accurately assessing the size and surface properties of potentially hazardous asteroids and impactors. Observations and modeling of an asteroid's thermal emission, which depends on its surface temperatures, lead to a direct size determination \citep{2015aste.book..107D}. Characterizing surface properties such as thermal inertia and roughness provides insights into regolith cohesion (surface strength) and internal structure (bulk density) \citep{2014Natur.512..174R}. Low thermal inertia values indicate surfaces that are dominated by finer particles, whereas higher thermal inertias suggest a higher fraction of boulders \citep{2022PSJ.....3...47M}.

Characterization of surface properties lends to accurate modeling of the surface temperature distribution, which depends on several factors. Key factors include the asteroid’s shape and spin parameters. Thermophysical models (TPMs) calculate surface temperatures based on shape and spin parameters, incorporating subsurface heat conduction and small-scale topographic effects (i.e., roughness) that cause shadowing and self-heating effects that influence the surface temperatures \citep{2022Icar..38815226M}. When the asteroid’s visual brightness is measured or estimated, its albedo can also be derived with the size calculated from infrared observations. Depending on the data quality and observing geometry, the thermal inertia and surface roughness can be constrained to some degree.

We present preliminary results for the shape, size, and thermal inertia of the potentially hazardous near-Earth asteroid (1566) Icarus. Lightcurve inversion modeling gives a top-spin shape that is characteristic of fast rotators \citep{2012Icar..220..514W}. Discovered in 1949, Icarus is rarely observed due to its small size and orbital configuration, which results in close Earth approaches only every 9, 19, or 28 years. Ground-based radar observations in 2015 \citep{Greenberg_etal17} resulted in an orbital drift measurement as a result of the Yarkovsky Effect \citep{2006AREPS..34..157B}. We incorporate this measurement into our shape and thermophysical modeling of thermal observations to constrain Icarus’s bulk density ($\rho_{bulk} = 2280^{+180}_{-150}\ \textrm{kg}\ \textrm{m}^{-3}$). From these parameters, we model its surface gravitational slopes shown in \autoref{fig:slopes}. Larger surface slopes found near the equatorial region are more susceptible to landslides and mass ejection \citep{2015Icar..247....1S}.

\begin{figure}
\centering
\includegraphics[width=0.75\linewidth]{Icarus_slopes.png}
\caption{Effective gravitational slopes calculated using a rotation period of 2.12 hr, a bulk density of $\rho_{bulk} = 2280 \ \textrm{kg}\ \textrm{m}^{-3}$, and size of 1.5~km.}
\label{fig:slopes}
\end{figure}

Using the MIRSI instrument at NASA's Infrared Telescope Facility we obtained new thermal infrared observations in June 2024 when Icarus approached Earth to within 0.21 au. Even at this close distance the total thermal emission was too weak to be detected from individual, sky-subtracted MIRSI frames. But the optical brightness was sufficient at visible wavelengths allowing us to guide the telescope using the MIRSI Optical Camera. By employing blind stacking of frames acquired over several hours on three separate nights, we were able to detect and measure its thermal emission at 10-$\mu$m. Using a TPM along with pre-existing shape and spin parameters, we estimate the asteroid’s size and surface thermophysical properties. We also obtained simultaneous absolute optical photometry with the IRTF's Opihi telescope/camera, enabling lightcurve observations that will be used to refine the shape model.

%Abstracts must be written in English and should be submitted to the IAA as Microsoft Word files (.doc, .docx) or Portable Document Format files (.pdf) within the deadline. All papers must be submitted online to iaapdc (at) iaamail.org It is recommended to proof read the paper before submission. Word format files are preferred but pdf format files will also be accepted.

\textbf{Comments:}

\textit{(Alternative session, Time slot, Oral or Poster, Etc...)}

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Abstract attached as a PDF file as required according to the guidelines.

Near-Earth object (NEO) models are a useful tool for interpreting asteroid behaviour in near-Earth space (perihelion distances < 1.3 au). They can predict many asteroid properties such the size-dependent transport from the main-belt (Granvik et al., 2018; Nesvorný et al., 2023) and the disruptive processes of low perihelia passage (Granvik et al., 2016; Wiegart et al., 2020). They can also estimate the frequency of Earth impactors (Harris & Chodas, 2021; Morbidelli et al., 2020) and trace the origins of meteorites to the main asteroid belt (e.g. Brown et al., 2023).

Models to date use telescopic data covering NEOs with diameters ranging from the order of a kilometre down to around 30 metres (absolute magnitude range H=17 to H=25). Calibrating models based solely on telescopically observed NEOs is a limitation when making predictions for smaller impacting meteoroids and meteorite precursors. We approach NEO modelling from a new direction and calibrate a NEO model to Earth impactors with data from the Global Fireball Observatory (Devillepoix et al., 2020), using more than 1,200 triangulated fireballs to probe the centimetre to metre-sized bodies. We present the modelling methodology and preliminary results, discussing the challenges of using a relatively smaller dataset.

References

Brown, P. G., McCausland, P. J. A., Hildebrand, A. R., et al. 2023, Meteoritics and Planetary Science, 58, 1773. Devillepoix, H. A. R., Cupák, M., Bland, P. A., et al. 2020, Planetary and Space Science, 191, 105036. Granvik, M., Morbidelli, A., Jedicke, R., et al. 2016, Nature, 530, 303. Granvik, M., Morbidelli, A., Jedicke, R., et al. 2018, Icarus, 312, 181. Harris, A. W. & Chodas, P. W. 2021, Icarus, 365, 114452. Morbidelli, A., Delbo, M., Granvik, M., et al. 2020, Icarus, 340, 113631. Nesvorný, D., Deienno, R., Bottke, W. F., et al. 2023, The Astronomical Journal, 166, 55. Wiegert, P., Brown, P., Pokorný, P., et al. 2020, The Astronomical Journal, 159, 143.

Keywords: Meteorite, meteor, Asteroid, Asteroid Families, Source Regions

To date, 74 meteorite falls have been instrumentally recorded by video cameras and still photographs and their pre-impact orbit determined. Two of which are the fall of Saint-Pierre-le-Viger from asteroid 2023 CX1 in France and the meteorite Ribbeck from asteroid 2024 BX1 in Germany.

A recent review paper takes stock of what we have learned so far about the source regions of our meteorites [1]. While six years ago there were only hints that different meteorite types approached on different orbits, now distinct patterns are emerging. Notably, the 10-cm to 1-m sized meteoroids
responsible for most of our meteorites arrive on different orbits than larger 10-m to 10-km NEA of corresponding taxonomic type. They do, however, identify the meteorite type of a number of asteroid families in the Main Belt.
Most notable is a source of H chondrites at low inclination just beyond the 5:2 mean motion resonance. This source is likely located in the Koronis family. Three of those meteorites have the about 7 Ma Cosmic Ray Exposure (CRE) age corresponding to the dynamical age of the Karin family within Koronis, one has the 12 Ma age of Koronis2 and one has an 83 +/- 11 Ma CRE age that may well be the age of the Koronis3 family.
There is also a source of H chondrites in the Inner Main Belt with an about 35 Ma CRE age. I will present arguments for why that is likely the Massalia asteroid family, which has a 40 Ma sub-family.

Other sources of H chondrites are high in the Central Main Belt, from where many of our H-like NEA originate. Two source regions are identified, one has the same dynamical age as the CRE age of the meteorites.

Most L chondrites arrive to Earth from a single source in the Inner Main Belt. I will present arguments for why that is likely the Hertha family (also known as the Nysa family).
Most LL chondrites arrive to us from the Inner Main Belt also, defining the petrographic and mineralogical properties of the Flora family.
In addition to these main ordinary chondrite groups, some other meteorite types have also provided approach orbits. We now know that CM chondrites originate from a low inclined source in the Central,
Pristine or Outer Main Belt. Possible sources are discussed. It has been long recognized that Vesta and its family are the likely source of most of our HED achondrites. Some are now traced to specific impact craters on Vesta. The source regions of other meteorite types are discussed also.

References
[1] P. Jenniskens, H. A. R. Devillepoix, Review of asteroid, meteor, and meteorite-type links, Meteoritics and Planetary Science (2024) submitted.

Keywords: Gravity Tractor, Slow-pull Mitigation Technique, Binary Asteroids, Mission Concepts

There are a number of possible mitigation strategies that have been identified in the event a hazardous asteroid is discovered. NASA’s DART mission recently demonstrated the kinetic impactor technique [1]. The gravity tractor (GT) is attractive as the next technology for demonstration since other techniques may be prohibited by cost and legality [2]. A GT demonstration mission would align with NASA’s goal to "[d]evelop preliminary mission designs for future NEO deflection mission campaigns” [3]. Here, we present the design of a mission that would demonstrate a GT by changing the orbit of the secondary in an asteroid binary system.

The GT concept for deflecting asteroids involves bringing a spacecraft near an asteroid and controlling the spacecraft so that the asteroid’s orbit is altered by the spacecraft’s gravity [4]. This slow-pull mitigation strategy can achieve greater precision in an asteroid’s post-deflection orbit than impulsive mitigation techniques. GT also has the benefits of being agnostic to the material properties of the asteroid and not requiring contact between the spacecraft and asteroid. A GT may be used as the “primary” mitigation technique for hazardous asteroids that are found sufficiently far in advance of their Earth impact dates, or as a “secondary” mitigation technique applied after a “primary” impulsive technique to ensure the avoidance of gravitational keyholes. Inspired by the success of the DART mission, we are studying whether GTs will be more easily tested in a binary asteroid system in the same way that kinetic impactors are: a small velocity change on the order of what would be necessary in a real emergency is more easily detected and measured on an asteroid satellite's orbit than it is on a single asteroid’s heliocentric orbit [5].

We report on the preliminary design of a GT demonstration mission to a binary asteroid system. We identify three main goals that a GT mission to a binary asteroid should achieve: (1) guide and navigate the spacecraft to the vicinity of the secondary and precisely control its relative position (within a few body radii), (2) measure the change in the secondary’s orbit due to the GT, and (3) demonstrate long-duration tractoring operations in close proximity to the asteroid. We present mission requirements needed to achieve these mission goals. These requirements are used to define a concept of operations for a binary asteroid system “characterization phase” and “tractor phase,” which would lead to a measurable deflection of the secondary within a 12-month timeframe for asteroid proximity operations. We present the mission design, baseline payload, and spacecraft design that would meet these investigation requirements. In sum, this report outlines a demonstration mission of a GT at reasonable cost that will accomplish NASA’s goal of demonstrating a slow-pull asteroid deflection technique.

References

[1] Chabot, N., et al. (2024). Planet. Sci. J. 5 49

[2] Abell, P. and Frazier (2021). Planetary Defense Missions: Rapid Mission Architecture Study. Planetary Science Decadal Survey: Mission Concept Study Report.

[3] NASA Planetary Defense Strategy and Action Plan (2023). NASA. https://go.nasa.gov/3UO2mmt

[4] Lu, E. T. and Love, S. G. (2005). Nature, 438, 177–178.

[5] Merrill, C., et al., this conference.

The Double Asteroid Redirection Test (DART) mission was a successful planetary defense demonstration of a kinetic impactor on Dimorphos, the satellite of binary near-Earth asteroid 63803 Didymos (Daly et al. 2023). The DART impact changed not only the orbit of the satellite Dimorphos about Didymos (Thomas et al. 2023), but also the orbit of the Didymos system about the Sun (Makadia et al. 2024). We report quantitative results of this heliocentric deflection, leading to a revised estimate of the momentum enhancement factor $\beta$ as well as an estimate of the bulk density $\rho$ of the target Dimorphos.

In the months following the DART impact, a series of stellar occultation campaigns led to a total of 18 observed occultations of the Didymos system from 2022-Oct-15 to 2023-Jan-22. These observations represent an exquisite astrometric data set, with reported errors of no more than a few milliarcseconds. Three of these observations were reported with <1 mas uncertainty, and the lowest reported uncertainty was 0.2 mas on 2023-Jan-22. With these measurements, the estimate of the Yarkovsky effect on Didymos became significantly more refined compared to the pre-impact estimates, but the effect of the DART deflection was not yet plainly discernible.

However, in 2024, observers detected three additional stellar occultations by Didymos, in May, August, and September. For reasons not yet fully understood, the May and August observations were discordant with each other, but either could fit well with the September occultation. After extensive analysis and discussion with the occultation teams, we have elected to use only the September occultation at present. The September measurement was judged the most reliable and we had no means of determining which of the other two observations should be favored, though it seems that one of them is likely reliable.

With the addition of the 2024-Sep-22 occultation, we estimate the change in velocity in a direction close to the heliocentric along-track direction to be ∆V = -12 ± 3 $\mu$m/s. This observable component of the deflection is only ~8.5$^\circ$ away from the system’s heliocentric velocity at impact. The deflection in orthogonal directions is essentially unconstrained. Given the known circumstances of the DART impact, this deflection implies $\beta$ = 2.0 ± 0.5, which is consistent with, but somewhat lower than, previous reports (Cheng et al. 2023). A lower value of $\beta$ implies a lower bulk density $\rho$ of Dimorphos, and indeed, using the measured deflection of the Dimorphos orbit around Didymos (Naidu et al. 2024), we estimate $\rho$ = 1.5 ± 0.4 g/cm$^3$, indicating that Dimorphos is significantly under-dense with respect to Didymos.

These results should be considered preliminary. Additional opportunities for occultation observations in early 2025, if successful, will serve to clarify the status of the neglected 2024 observations and further improve the associated estimates.

Several techniques may be appropriate for deflecting a threatening asteroid on a collision course with Earth. Slow-push techniques, such as gravity tractors, require long lead times. Fast-push techniques such as nuclear standoff bursts require much less lead time but come with a host of additional issues. Kinetic impactors are an alternative fast-push technique that can be used on small-to-medium hazards with moderate warning time. The Double Asteroid Redirection Test (DART) mission showed the efficacy of the kinetic impactor technique when it successfully changed the orbital period of Dimorphos in 2022. Despite the success of the DART mission, questions still remain about the efficiency of momentum transfer with this technique. Modeling work performed in support of DART suggests that properties such as material strength, porosity, crush properties, asteroid internal structure, and inherent flaw distribution, can significantly affect the deflection that will be caused by a kinetic impactor. Here, we undertake a set of experiments to better constrain how material strength and target structure affect the outcomes of kinetic impactor asteroid deflection.

We constructed “designer asteroids” with varying internal structures, from coherent asteroids to rubble piles, and performed impact experiments at the Johns Hopkins Applied Physics Laboratory (APL) Impact Lab and the NASA Ames Vertical Gun Range (AVGR) to evaluate the momentum transfer efficiency following impact. Impact velocities ranged from 0.15-0.35 km/s at the APL impact lab, to 1-2 km/s at the AVGR. Spherical targets were created using a range of well understood plaster materials of varying strengths. Rubble piles were created using plaster matrix material surrounding either aquarium gravel or porous pumice. All these plasters have well characterized strength properties ranging from 10 to 117 MPa. The internal structure of the targets were evaluated using x-ray CT scans, the shape and volume of the craters and resulting deformation was tracked, and a ballistic pendulum was used to track deflection.
High-speed videos were used to measure the impact location and angle and to determine the displacement and rotation of the target following impact. We used particle and object tracking algorithms to compute the horizontal, vertical and lateral displacements, and the rotations of the pendulum to determine post-impact momentum. We also measure the ejection speed and direction of target ejecta, to understand the origin of any momentum enhancement, and characterize the shape and mass of the largest individual ejecta.
Differences in momentum enhancement are seen across velocity and target structures. We find that more porous targets do not generate significant ejecta and likely cause less momentum change, which is consistent with findings in the literature. We also note that impact angle significantly alters the linear momentum transferred. Strength differences in less porous target show greater momentum changes relative to the mounting plaster, but show subtle changes when compared to each other with stronger targets possible showing less efficient momentum enhancement. Rubble pile targets behave noticeably differently than homogenous targets. In this presentation, we will describe the initial experiments, results, and discuss internal structure effects on deflection.

The vast majority of asteroids that pose a threat to Earth have a complex distribution of porosity due to their rubble-pile configuration. As of right now the only proven method for deflecting these potentially hazardous bodies is to use a kinetic impactor, as was demonstrated by the Double Asteroid Redirection Test (DART) mission. Kinetic impacts change the momentum of the target asteroid through the transfer of momentum of the impactor to the body and through the resulting ejection of material away from the target body. There are multiple material properties that affect the ejection of material from kinetic impacts, one of which being porosity, which plays a significant role in the cratering process. The crushing of pore space is an irreversible process that dissipates shock waves and decreases the free energy of the system. Additionally, the type of porosity, such as large open voids between individual boulders (macroporosity) and small well distributed voids within the boulders themselves (microporosity), could play a significant role during the creation of ejecta.

We have begun systematically testing how porosity distributions affect the deflection of rubble-pile asteroids by kinetic impacts using simulations performed with the Smooth Particle Hydrodynamics (SPH) code Spheral++. Spheral++ has recently been updated to include a Soft-Sphere Discrete Element Method (SSDEM) physics package. For this project, we first assemble our rubble-pile asteroids in the SSDEM package and then hand off the configuration to SPH to model the hypervelocity kinetic impact. We initialize the rubble piles with varying amounts of macro- and microporosity and observe the changes in ejected material to determine how the asteroid’s momentum changes accordingly. For the initial foray into this project, all simulations are performed in 2D to reduce simulation time and determine overall trends in impact response. We find that the inclusion of resolved macroporosity greatly reduces ejecta generation compared to an otherwise identical simulation with a microporous monolithic target and therefore significantly influences the deflection of asteroids. Our preliminary results demonstrate that, when designing asteroid deflection missions, the effects of both macro- and microporosity should be considered to accurately model the response of rubble-pile asteroids to mitigation attempts.

LLNL-ABS-2001234

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

HYPERVELOCITY CRATRING AND DISRUPTION OF THREE L-TYPE ORDINARY CHONDRITES

George J. Flynn(1), Melissa Strait(2), Daniel Durda(3) and Robert Macke(4)
1Dept. of Physics, SUNY-Plattsburgh, 101 Broad St., Plattsburgh, NY 12901 USA (01-518-564-3163, flynngj@plattsburgh.edu),
2Dept. of Chemistry, Alma College, Alma, MI 48801 USA (straitm@alma.edu),
3SwRI, 1050 Walnut St., S-300, Boulder CO 80302 USA (durda@boulder.swri.edu).
4Vatican Observatory, V-00120 Vatican City-State (rmacke@specola.va),

Keywords: Asteroid Deflection, Momentum Enhancement Factor, Disruption Energy

The response of asteroids to hypervelocity impact influences momentum transfer in cratering and fragmentation in disruptive collisions, which together limit the maximum change in velocity (VMAX) that can be imparted by a single kinetic impact. For Qc, the energy per unit target mass for onset of fragmentation,, the ratio of impactor momentum to momentum acquired by the target, and vi, the impactor mass:
VMAX = 2Qc/vi [1].
Hydrocode modeling indicates decreases with increasing target porosity, and, QD, the energy for the onset of catastrophic disruption, increases with increasing target porosity or decreasing target strength. To test this, we performed hypervelocity cratering and disruption experiments on three asteroid samples of similar compositions but different porosities (P): the low porosity L3 Ordinary Chondrite (OC) meteorite Aba Panu (P ~3%), intermediate porosity L3-6 OC Northwest Africa 869 (NWA 869) (P ~8%), and high porosity L4 OC Saratov (P ~14%).  followed the expected pattern:  = 3.5 for Aba Panu, 2.7 for NWA 869, and 2.5 for Saratov. However, the decrease in  is not as strong as suggested by modeling, which indicates that  should be <1.2 for targets with a porosity as high as Saratov. Although modeling indicated the energy required for catastrophic disruption should increase with porosity, our results deviated from this, with the highest porosity target Saratov having QD = 1,079 J/kg, comparable to the low-porosity OC Aba Panu (QD = 1,148 J/kg) but much lower than the 1,795 J/kg for the intermediate porosity OC NWA 869. Saratov’s low QD may result from the unusual structure of OC meteorites, consisting of strong, spherical chondrules embedded in porous, weaker matrix. As the amount of matrix is reduced, the porosity of OCs increases, and strength decreases. Love et al. [2] proposed a formula for disruptive events, where QD ∝ S0.45. Using this approach, we found a power law behavior (Figure 1) between QD/S0.45 and (1 – porosity), indicating that, for these three L-type OCs, the dependence of QD on strength can be separated from the dependence on porosity. Further, we determined Qc, the energy per unit target mass for the onset of fragmentation, from a plot of the impactor kinetic energy vs the mass of the largest fragment to the target mass, and calculated VMAX for an ~5 km/s impactor speed: 0.81 m/s for Aba Panu, 1.72 m/s for NWA 869, and 0.84 m/s for Saratov. The small difference between these VMAX values, compared to the factor-of-seven difference we reported between NWA 869 and the anhydrous carbonaceous chondrite NWA 4502 [1], suggests remote sensing showing an asteroid is similar to L-type OCs may be sufficient for selecting the impactor mass and speed for kinetic impact deflection that avoids significant fragmentation.

Figure 1: Log-log plot of Q*D/S0.45 vs. (1 - porosity) for three L-type OCs shows a linear behavior, indicating the effects of strength and porosity can be separated.

References: [1] G. J. Flynn et al., (2023) Proceedings of HVIS 2022, V001T06A002. doi.org/10.1115/HVIS2022-16. [2] S. G. Love et al. (1993) Icarus, 105, 216-224.

In an idealized mitigation scenario, one would strive for threat interception to occur as far away–in both space and time–from Earth as possible. However, reality may make such a desirable outcome improbable to impossible, due to hurdles like uncertainty in the threat's characteristics or lack of time for preparation. In a scenario where extended warning time and preparation are out of reach, it is imperative to consider terminal mitigation methods. We analyze the effectiveness of mitigation via intentional robust disruption (IRD) for objects similar to 2024 PDC25, the 90-160 m diameter threat described in the 2025 Planetary Defense Conference (PDC) Hypothetical Asteroid Impact Scenario.

Pulverize It (PI) is a planetary defense concept which is designed to operate in both short-warning and extended time scale interdiction modes, representing a unique multi-modal approach to asteroid threat mitigation. PI is under development as part of a NASA Innovative Advanced Concepts (NIAC) Phase II study. The method utilizes high-density hypervelocity impactors to penetrate and fragment an incoming asteroid. In extended warning scenarios in which the asteroid is intercepted far from Earth, PI can be used for either robust disruption via complete fragmentation or enhanced deflection via partial fragmentation. In short-warning scenarios, PI can be used in a terminal mode to disrupt an incoming asteroid into small fragments (<10 m diameter) which then intercept Earth, resulting in a series of high-altitude airburst events with spatial and temporal spread. This yields ground-level optical pulses and de-correlated shock waves which distribute the energy of the parent asteroid.

PI represents the first planetary defense method with multi-modal capability and with the ability to respond to rapid, short-warning threats. We compare PI to kinetic impact (deflection) by simulating mitigation of a Dimorphos-scale (160 m diameter) asteroid model to compare with NASA's Double Asteroid Redirection Test (DART) mission. We find that, in general, PI requires a lower launch mass than kinetic impact missions for the same threat, which enables a fully capable planetary defense system that relies solely on pre-existing launch vehicles. Our simulations support the proposition that PI is an effective multi-modal approach for planetary defense, particularly for objects within the diameter range of 2024 PDC25, even in terminal interdiction modes which yield ground effects that are vastly less damaging in comparison to unmitigated cases.

Certain planetary defense scenarios may require the use of nuclear explosive devices (NEDs) for successful mitigation [1]. Planning for these scenarios use engineering models derived from hydrocode simulations, themselves built upon models of x-ray energy deposition in asteroid material [2]. Recent work [3] has advanced the state-of-the-art in energy deposition modeling using radiation-hydrodynamics simulations. Though radiation-hydrodynamics processes begin to dominate at typical scenario x-ray fluences, the experimentally accessible x-ray fluences available at facilities such as OMEGA [4] are low enough that re-radiation of deposited energy is minimal, and cold opacities are sufficient to describe the x-ray energy deposition [5]. These levels are still sufficient to generate the material ablation and blowoff processes that serve as the momentum transfer mechanism in NED planetary defense scenarios, and are constrained by material-dependent properties.

In this work, we present a calibration of x-ray energy deposition models derived from broadband x-ray exposure experiments conducted at the OMEGA laser. Several geologic and meteoritic samples were exposed to various x-ray fluence levels over a multi-shot experimental campaign. On each shot, a specialized target [6,7] is illuminated by the OMEGA-60 laser system, generating a broadband flash of x-rays which irradiate the surfaces of the samples. Energy deposited by these x-rays initiate low-fluence ablation and blowoff processes. Following exposure, post-shot profilometry techniques are applied to determine the quantity of material removed in the experiment. The provides a key measurement of material removal depth, a quantity needed to calibrate ablation and impulse models. This low-fluence calibration in turn anchors radiation-hydrodynamics models and ties them to empirically accessible regimes.

This work was funded by a NASA Research Opportunities in Earth and Space Sciences (ROSES) 2022 Yearly Opportunities for Research in Planetary Defense (YORPD) grant (NASA Grant Number: 22-YORPD_22_2-0005) under the Near-Earth Object Observations Program. Part of this work was performed under the auspices of the Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-871535.

[1] Dearborn, D.S.P. and P.L. Miller, “Defending Against Asteroids and Comets”, in Handbook of Cosmic Hazards and Planetary Defense (J.N. Pelton and F. Allahdadi, eds.), Ch. 34, pp. 733-754, Springer International Publishing Switzerland, 2015.

[2] Dearborn, D.S.P., M.B. Syal, et al., Options and Uncertainties in Planetary Defense: Impulse-Dependent Response and the Physical Properties of Asteroids, Acta Astronautica Vol. 183, pp. 29-42 (2021).

[3] Burkey, M.T., R.A. Managan, et al., X-Ray Energy Deposition Model for Simulating Asteroid Response to a Nuclear Planetary Defense Mitigation Mission, PSJ Vol. 4, p. 243 (2023).

[4] Davis, A.K., M.B. Airola, et al., Thermal Response Measurements for OMEGA-Laser-Generated Environments, JRERE Vol. 42 No. 1 pp. 35-40 (2024). (CUI Document.)

[5] King, P.K., D.M. Graninger, et al., Modeling the Dynamic Thermomechanical Response of Materials to X-Ray Irradiation, JRERE Vol. 42 No. 1 pp 41-49 (2024). (CUI Document.)

[6] Perez, F., J.J. Kay, et al., Efficient Laser-Induced 6-8 keV X-Ray Production from Iron Oxide Aerogel and Foil-Lined Cavity Targets, PoP 19, 083101 (2012).

[7] Girard, F., Review of Laser Produced Multi-keV X-Ray Sources from Metallic Foils, Cylinders with Liner, and Low Density Aerogels, PoP 23, 040501 (2016).

This study presents a groundbreaking experiment that explores the deflection of Near-Earth Objects (NEOs) using x-rays generated from a stand-off nuclear explosion for deflecting the largest NEOs or for short impact warning times. Conducted at the Z Machine at Sandia National Laboratories, our innovative approach utilized an intense x-ray burst produced by an argon plasma, targeting miniature mock asteroids made of silica (see N.W. Moore, M. Mesh, J. J. Sanchez, et al., Simulation of asteroid deflection with a megajoule-class X-ray pulse, Nat. Phys. (2024), https://doi.org/10.1038/s41567-024-02633-7). In this experiment, we employed “x-ray scissors” to release the targets into free space nearly instantaneously. This novel technique allowed the mock asteroids to move freely in a vacuum, closely mimicking the conditions that NEOs would experience in space. We utilized laser interferometry to accurately track the motion of the mock asteroids, which achieved speeds of ~70 m/s. Scaling our findings, which align with numerical simulations, provides experimental confirmation for the potential to deflect kilometer-scale asteroids using stand-off x-ray bursts. This new experimental capability paves the way for evaluating the effectiveness of nuclear deflection of various asteroid materials in a controlled laboratory environment, i.e., without space flight. We detail the experimental setup and results, including analysis showing that allowing the mock silica asteroids to move freely enhances momentum coupling to the target by ~30-50%, representing a significant advancement in our understanding of asteroid deflection techniques.
Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525.

Planetary defense mitigation attempts require significant advanced mission planning and simulation. The modeling work is conducted using hydrodynamics codes and equation of state data (Barbee et al., 2018). The results of these pre-launch simulations are used in mission planning to predict targeting and timing requirements and to quantify the energy and delivery mechanism required to deflect or disrupt the threat object. The hypothetical threat object 2024 PDC has a moderate size and warning time relative to current response capabilities. Non-nuclear means would likely be the preferred response to such a threat. Even in such cases, nuclear mitigation is a potential last-resort response if other methods fail. Because it is seen as a back-up option for this scenario, we explore how nuclear mitigation might work in the context of failed previous non-nuclear mitigation attempts, including an exploration of uncertainties in the planning and simulation of such a mission. Initial scaling estimates based on the size of craters produced in above ground nuclear tests (Glasstone and Dolan, pp. 253-257) suggest that it may be possible to disrupt a threat object similar to those described in exercise epoch 1. We will present the results of higher fidelity physics simulations like the one shown in Fig. 1 below at the meeting which will include material properties specific to the epoch 2 property range for the hypothetical threat object and x-ray transport from energy sources in vacuo. These simulations use the Cassio radiative transport hydrocode described and validated for use with porous silicates in Falk (2014). We will explore the effects of the epoch 2 material property variance on our predictions, and lead times required for safe mitigation.

Fig. 1: A temperature plot [eV] from a physics simulation of a 10 kt burst 83 m above a 200 m bi-lobate porous silicate target that included hydrodynamics, x-ray transport, heat transport, and material strength.

Keywords: Nuclear mitigation modeling, deflection, disruption, hydrocode

Asteroid impacts are serious natural disasters that may result in regional to global damage depending on the object’s mass and incoming velocity. However, with adequate preparation time, we may be able to prevent impacts from happening. One such mitigation method is the “kinetic impactor” method, which involves deliberately impacting the asteroid threat with a spacecraft, as demonstrated by NASA’s Double Asteroid Redirection Test mission [1], [2]. For exceptionally massive asteroids or situations where there is insufficient time for a kinetic impactor to be effective, we could rely on nuclear mitigation methods to deflect or intentionally and robustly disrupt the object. In such scenarios, a nuclear explosive device (NED) can be detonated a distance away from the asteroid (the “height of burst” or HOB), producing a wealth of X-rays that heat and ablate the target’s surface. With sufficient energy, the ablated material will escape the asteroid’s gravitational pull, causing a change in the asteroid’s momentum, and subsequently, its orbit [3]. For cases in which accidental fragmentation from a deflection mission is possible, or if there is not enough time to execute a deflection mission, we could robustly disrupt the asteroid into many small, fast-moving fragments that pose no threat to Earth by using an NED with larger yield at a smaller HOB.

Currently, a common guideline for assessing intentional disruption events is whether the asteroid is deflected at a velocity exceeding 10 times the escape velocity. Whether this heuristic holds for nuclear mitigation methods has yet to be comprehensively tested. High-fidelity nuclear disruption simulations can be used to fill this knowledge gap and are thus crucial for well-informed mitigation mission design. We use the smoothed particle hydrodynamics (SPH) code Spheral to generate 3D simulations of asteroids and initialize them with an X-ray energy deposition model to simulate the effects of a nuclear device [4]. The left panel of Figure 1 shows the initial specific thermal energy deposited by the X-ray energy deposition model for a Bennu-shaped asteroid where lighter shades of green indicate larger initial energy values. Preliminary data from our Spheral simulations show broad agreement with previous deflection results in [4].

We present an exploration of robust disruption results for both Bennu-shaped and Itokawa-shaped asteroids scaled down to a diameter of 150 m. The right panel of Figure 1 illustrates a potential disruption event for a Bennu-shaped asteroid approximately 65 ms after the NED first illuminates the surface. The material is color-coded by velocity magnitude, with lighter shades representing higher velocities. By modeling and analyzing disruption simulations, we will help to define the regime in which robust disruption is a viable option compared to deflection missions, ultimately contributing to the development of effective planetary defense strategies.

Figure 1. Left: A Bennu-shaped asteroid in Spheral, showing the specific thermal energy after initialized with the X-ray energy deposition model from [4]. Right: The Bennu-shaped asteroid approximately 65 ms after the energy deposition, where material is rapidly blown-off from the surface (color-coded by velocity magnitude).

Prepared by LLNL under Contract DE-AC52-07NA27344.
LLNL-ABS-871345

[1] R. T. Daly et al., "Successful kinetic impact into an asteroid for planetary defence," Nature, vol. 616, no. 7957, pp. 443-447, Apr 2023, doi: 10.1038/s41586-023-05810-5.
[2] A. F. Cheng et al., "Momentum transfer from the DART mission kinetic impact on asteroid Dimorphos," Nature, vol. 616, no. 7957, pp. 457-460, Apr 2023, doi: 10.1038/s41586-023-05878-z.
[3] D. P. S. Dearborn and P. L. Miller, "Defending Against Asteroids and Comets," in Handbook of Cosmic Hazards and Planetary Defense. Cham: Springer International Publishing, 2015, pp. 733-754.
[4] M. T. Burkey, R. A. Managan, N. A. Gentile, M. B. Syal, K. M. Howley, and J. V. Wasem, "X-Ray Energy Deposition Model for Simulating Asteroid Response to a Nuclear Planetary Defense Mitigation Mission," The Planetary Science Journal, 2023.

Asteroid impacts, though infrequent, have the potential for catastrophic consequences. Space missions offer the possibility of averting such disasters, provided there is adequate warning time and decisive action. Successfully mitigating a potential asteroid impact relies on decision-makers swiftly comprehending the complex mission space and committing to a course of action with enough time for the mission to be fully executed. The Asteroid Mitigation Response plot, sometimes referred to as Dearborn Plot (Figure 1), is a widely referenced figure that has served as a longstanding guide on deciding which mission strategies might best mitigate an impact based on asteroid size and warning time. It was first published in the National Research Council 2010 report on Planetary Defense[1] and later updated in 2015[2]. Since then, there have been substantial advancements in the field, notably with the establishment of the U.S. Planetary Defense Coordination Office and the Double Asteroid Redirection Test.

We present a timely revision of the Asteroid Mitigation Response plot that reflects current mission-design thinking. It incorporates a broader statistical analysis of mission options and asteroid trajectories, reflecting the latest technological and strategic developments. The scenarios are sampled from a suite of realistic, Earth-impacting orbits, excluding those with significant pre-impact encounters with Earth (such as those with keyholes) which inject a degree of chaos into deflection modeling. The potential impact locations are randomly generated along the risk corridor. A mission scenario is considered “successful” if a single mission launched by a Falcon Heavy 1) can deflect the asteroid off Earth from 90% of the potential impact locations without even a weak disruption that would result in a hazardous debris field or 2) robustly disrupt the asteroid into small, fast-moving fragments that pose no threat. The plot will explore deflection through kinetic impactors (KI), deflection using an ion beam, and deflection or disruption via a nuclear explosive device (NED). The KI missions are informed by realistic ballistic trajectories and incoming velocities while sampling from a range of likely $\beta$ values. The NED deflection missions are selected for feasibility based on recently updated deflection velocity ($\Delta V$) analytic models and the disruption likelihood will be informed by simulations. The ion-beam deflection calculations assume the deployment of 20 kW NEXIS thrusters and a highly controlled $\Delta V$. The methodology will build on analysis presented at the 2024 IEEE Aerospace Conference by Paul Chodas in support of further developing/testing the ion-beam mission type (as seen in Figure 2).[3]

By updating the Asteroid Mitigation Response plot based on recent insights, we hope to better guide decision-makers to immediately focus on effective mitigation strategies, thereby maximizing the odds of successful mission, should one be needed.

Keywords: Planetary Defense, Flyby, Spacecraft Reconnaissance, Near-Earth Object

International and U.S. strategies have identified the need to develop spacecraft reconnaissance capabilities as a priority to advance planetary defense readiness. The UN-endorsed Space Mission Planning Advisory Group and the US Report on Near-Earth Object Impact Threat Emergency Protocols recommend planning a spacecraft reconnaissance mission in any scenario where 1) Earth impact is predicted to be within <50 years, 2) impact probability is assessed to be >1%, and 3) the object is characterized to be >50 m in size (or absolute magnitude (H) of <26). Given these thresholds, the 2023 U.S. Decadal Survey for Planetary Science and Astrobiology recommended that the highest priority for the next planetary defense demonstration mission is a rapid-response, flyby reconnaissance mission targeted to a small NEO as a challenging case for the capability. The 2023 U.S. National Preparedness Strategy and Action Plan for Near-Earth Object Hazards and Planetary Defense and the 2023 NASA Planetary Defense Strategy and Action Plan both identify the short-term action of planning for the development, testing, and implementation of NEO reconnaissance mission systems.
To develop a robust flyby reconnaissance capability for planetary defense, we have developed four major requirements to define a demonstration mission:
1) Enable a flyby of >90% of the potential asteroid threat population – our analysis shows that flyby speeds of up to 25 km/s and approach solar phase angles as high as 90° have to be accommodated within the mission’s capabilities to meet this requirement.
2) Demonstrate the flyby reconnaissance for a ~50 m NEO – 50-m objects are the smallest recommended for a space-based response, providing the stressing case for the capability.
3) Obtain the information needed to determine if and where it would impact the Earth – planning for a reconnaissance mission is recommended if Earth impact is >1%, and hence determining if the object will impact the Earth and if so, constraining the impact swath location on the planet, is a top priority.
4) Determine key properties of the asteroid to inform decision makers – While in any threat situation, as much information as possible is always desired, our analysis identifies four key properties that are the priorities: size, rocky vs. metallic composition, single vs. multiple objects, and surface characteristics.

Applying this capability to the 2025 PDC Hypothetical Asteroid Impact Scenario, which has crossed the recommended thresholds for mission planning, we show how the data obtained by the flyby reconnaissance we have defined would greatly increase the knowledge of the potential threat to inform the subsequent planetary defense response.

Thanks to the success of NASA's DART mission, the Kinetic Impact (KI) method is the only tested way of deflecting Near-Earth Asteroids (NEAs) away from the Earth [1]. However, one important consideration with KI deflections is the potential of disrupting the target while trying to deflect it. A disruption can happen if the NEA is small or if the relative impact momentum of the deflection spacecraft is too high. Recent studies indicate that unintended fragmentation of the asteroid can be avoided if the change in velocity ($\Delta V$) of the asteroid due to a KI mission is less than 10% of its surface escape velocity [2]. Previous studies have proposed doing multiple, smaller deflections to avoid disrupting the target [3] and to increase the momentum transfer efficiency for targets with high curvature [4]. Campaigns with multiple KI spacecraft also offer redundancy in case one spacecraft fails to hit the target.

In order to safely conclude whether the threat from an impacting NEA has been mitigated (using one or more deflection spacecraft), we must estimate its $\Delta V$ as a result of the deflection. Doing so requires observations of the NEA both before and after the deflection event. The fastest method of acquiring these measurements is to have a reconnaissance spacecraft in orbit around the target. In this scenario, spacecraft tracking data can be converted to meter-level geocentric pseudo-range measurements, as was done by the OSIRIS-REx spacecraft at (101955) Bennu [5].

In this work, we provide timelines for estimating the $\Delta V$ for a deflection of the hypothetical asteroid 2024 PDC25. We assume the presence of a reconnaissance spacecraft that can be tracked around the target NEA before and after deflection. Using this tracking data, we look to place constraints on the minimum time required to estimate the $\Delta V$ after a deflection. This is especially important for campaigns with multiple deflections because the uncertainties in the target's position compound after each deflection. Although we only apply this analysis to the hypothetical asteroid threat exercise based on asteroid 2024 PDC25, we aim to generalize our results for any impacting asteroid.

Preliminary results show that the minimum time between deflections in a multiple KI campaign for 2024 PDC25 needs to be at least a couple of weeks to confidently estimate the preceding $\Delta V$ before the next. Adhering to this constraint would enable decision-making ability between deflections and allow us to conclude whether the asteroid has been sufficiently deflected during the campaign. If this constraint is violated, our ability to reassess the asteroid's impact threat between deflections would be significantly affected. In this scenario, the campaign would have to follow a preset strategy without the ability to update it after each deflection. We would be able to conclude whether the impact threat from the NEA has been mitigated only after all the deflections were complete.

References
[1] N. L. Chabot et al., Achievement of the Planetary Defense Investigations of the Double Asteroid Redirection Test (DART) Mission, The Planetary Science Journal 5 (2024) 49.
[2] K. M. Kumamoto, B. W. Barbee, J. Pearl, M. B. Syal, Probing Disruption Heuristics for Kinetic Deflection of Asteroids, in: 2024 American Geophysical Union Meeting.
[3] Committee to Review Near-Earth Object Surveys and Hazard Mitigation Strategies, Defending Planet Earth: Near-Earth-Object Surveys and Hazard Mitigation Strategies, National Academies Press, 2010.
[4] M. Hirabayashi et al., Kinetic deflection change due to target global curvature as revealed by NASA/DART, Nature Communications In press (2024).
[5] D. Farnocchia et al., Ephemeris and hazard assessment for near-Earth asteroid (101955) Bennu based on OSIRIS-REx data, Icarus 369 (2021) 114594.

The discovery of a new Near-Earth Object (NEO) with a significant probability of impacting the Earth will inevitably lead to threat mitigation strategies. Three key questions for threat mitigation are: (i) what is the probability that the object impacts the Earth?; (ii) Is the object large enough to threaten loss of life or property?; and (iii) what are the key characteristics of the object required to plan a mitigation strategy and mission? Rapidly addressing these three questions maximizes the time available on the ground to mitigate the threat of an impact.

The authors participated in a workshop in October 2022 at the Keck Institute for Space Studies (KISS) titled “Enabling Fast Response Missions to NEOs, ISOs, and LPCs” to identify promising mission concepts and technologies that would enable rapid response approaches to potentially hazardous asteroids (PHAs). Concepts investigated included pre-designed systems ready to be implemented, pre-manufactured systems ready to be launched, and systems launched to various staging orbits ready to be tasked to reconnoiter a recently discovered object. Advantages and disadvantages of each concept were explored in detail in the published study.

The workshop study concluded that there are significant opportunities for partnerships between governments, traditional aerospace companies, and emerging aerospace entities. Emerging small spacecraft capabilities offer the potential to reduce cost and schedule significantly, but at the cost of lower payload mass and higher risk. Furthermore, while there are many concepts for rapid response, there is no consensus approach to assessing proposed concepts. Rapid response concepts must be capable of successfully encountering future identified potential PHAs and returning key orbital properties (to determine impact probability and location) and physical properties (to inform mitigation techniques). Additionally, implementable concepts also need to be demonstrably viable by fitting within programmatic constraints including but not limited to the cost, schedule, launch capabilities.

In this paper we describe the conclusions of the KISS workshop in October 2022, identify key technology gaps to enable the reconnaissance of PHAs, and propose an approach to assess the merit and feasibility of mission concepts for PHA reconnaissance. We also provide recommendations for future study of programmatic and technical requirements and constraints that may facilitate future, implementable mission concept development for rapid response reconnaissance. Finally, we discuss how the development of this capability has feed-forward opportunities to explore long-period comets or interstellar objects, which have similar rapid-response requirements as PHAs.

Acknowledgements: We thank all the participants for their time, enthusiasm, and contributions to the workshop and the final report. We acknowledge critical support from the W. M. Keck Institute for Space Studies, and JPL/Caltech, under contract with NASA (80NM0018D0004). Finally, we thank Michele Judd, Janet Seid, and the KISS staff for their enthusiasm, dedication, and skill in planning and convening this workshop. D.Z.S. is supported by an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-2303553. This research award is partially funded by a generous gift of Charles Simonyi to the NSF Division of Astronomical Sciences. The award is made in recognition of significant contributions to Rubin Observatory’s Legacy Survey of Space and Time.

The 2023 National Academy of Sciences, Engineering, and Medicine Decadal Survey on Planetary Science and Astrobiology lists several key questions regarding the collisional, dynamical, and physical evolution of small body populations in the solar system. Among those objects are Temporarily Captured Orbiters (TCOs), a subset of near-Earth objects (NEOs) that enter the Earth-Moon system and become temporarily captured by Earth’s gravitational field, orbiting as a natural satellite or “mini moon” of the Earth before exiting the Earth-Moon system sometime thereafter. TCOs remain largely unstudied, in part due to a lack of data from both ground- and space-based telescopes. TCOs present a unique opportunity for studying bodies external to our Earth-Moon system without the need for expensive deep-space missions to investigate them. This paper will present the mission concept of Mini-Luna, a cislunar mission designed by students from Cornell University’s Smallsat Mission Design School (SMDS), tailored for NASA’s Small Innovative Mission for Planetary Exploration (SIMPLEx) program. The Mini-Luna mission concept, with its 12U TCO Rendezvous Explorer (TREx) CubeSat, aims to demonstrate the viability of smallsat form factors for traveling to, rendezvousing with, and in-situ characterization of TCOs, thereby also addressing gaps in our knowledge about the TCO population. Historically, no spacecraft has visited a TCO, highlighting the Mini-Luna mission as a novel scientific and technological pursuit. The TREx technology demonstration can also be a potential minimum viable product (MVP) for future small body targets.

After the commissioning of the Vera C. Rubin Observatory in August 2025, its nightly surveys are expected to discover one TCO every two to three months, on average, yielding a total of approximately 75 TCOs during the ten year lifetime of the Legacy Survey of Space and Time (LSST) [1]. At the same time, the total number of known small bodies in The Solar System is expected to increase by a factor of 10 to 100 [2]. Our mission will begin with a rideshare in the 3rd quarter of 2030, where TREx will be transported via a Falcon Heavy rocket and released into a Near-Rectilinear Halo Orbit (NRHO) about the Earth-Moon L2 Lagrange point. TREx will stay in an L2 parking orbit until a suitable TCO is detected by ground-based observations and deemed reachable by the mission operations team. Once the TCO is selected, the spacecraft will leave its parking orbit and rendezvous with the TCO to collect images of it and characterize its size, shape, and surface composition. The instrument payload will include two cameras: one with a wide field of view that operates in the visible spectrum, and another based on the specifications of an ESA Hera mission instrument, which is a visible-near-infrared multispectral imager [3]. During End-of-Life operations, TREx will be injected into a disposal orbit that leaves the Earth‒Moon system, complying with NASA Procedural Requirements for Limiting Orbital Debris.

SIMPLEx program constraints include a maximum allowable budget of 55 million USD, a mass limit of 180 kg, and a volume restriction of 12U. The final estimates for the proposed two year mission are calculated to be 24 million USD, 27 kg mass, and 11.8U volume. The proposed Mini-Luna mission concept will provide more information on small body populations and pave the way for future TCO technology demonstrations.

As part of the ALCOR program, the Italian Space Agency (ASI) is funding the "Asteroid Nodal Intersection Multiple Encounters (ANIME)" CubeSat mission, which successfully completed Phase A in 2024. The aim is to develop a 12U CubeSat tailored for the exploration of multiple near-Earth asteroids (NEAs) encountered during their transits through their orbital nodes.

ANIME's baseline mission profile encompasses flybys with two Potentially Hazardous Asteroids (PHAs) and a rendezvous with a small NEA measuring in the tens of meters. The selection of mission targets is based on their distinctive physical and orbital characteristics, rendering them exceptionally intriguing for both scientific research and planetary defense considerations. In particular, the baseline rendezvous target has been identified in 2000 SG344. This NEA is classified among the more dangerous asteroids in JPL and ESA risk lists, with multiple potential collision solutions with our planet during the course of the next century. It is also considered an excellent target for future human exploration thanks to its accessibility.

The system architecture is based on flight-proven components, featuring a scientific payload comprising two cameras and an onboard transponder for acquiring radio science data. By leveraging these components, ANIME aims to provide valuable insights into the latest theories concerning planetary formation scenarios. Noteworthy, such information will be also relevant for planetary protection purposes, as well as to assess a potential near-future exploitation of asteroid resources. Additionally, the mission seeks to validate critical technologies essential for CubeSat exploitation in deep space, expanding their proven performance to this challenging domain. The presentation will outline the results of the phase A study.

The lessons of reusing and repurposing mission assets are relevant to Planetary Defense and Small Body Science objectives, as expressed in the most recent decadal survey for Planetary Science and Astrobiology. As described in [1], the European Service Module (ESM), the element of NASA’s Artemis Program that returns the Orion Crew Module to Earth (Figure), currently is planned for destruction by burning up in the Earth’s atmosphere. However, the ESM is a capable spacecraft, complete with propulsion, attitude control, power generation/conditioning/distribution, thermal control, and payload support. By leveraging the remaining propulsive capabilities, post separation, it has the potential to provide a near term method, on a yearly cadence, at a reduced cost, for achieving science return across an array of mission types.

JPL hosted a scientific workshop in summer 2024, with US and European participants, to discuss potential ESM extended mission targets. The participants jointly assessed the benefits that could be derived from repurposing the ESM for scientific use after completing its primary mission. The participants generated over thirty concepts that offered significant value in areas such as planetary defense, planetary science, the exploration of Near-Earth Objects (NEOs), and cosmology. For example, there are many unexplored classes of near-Earth and main belt asteroids that could be reached with the ESM after its primary mission. Some of these bodies are associated with water (e.g., 24 Themis), others with metals (e.g., 216 Kleopatra), and others imply impact hazards. The ESM, in principle, can tour several diverse asteroids and possibly carry a small NEO sample return spacecraft [2], rapidly accelerating our understanding of these worlds. Another concept highlighted the capability to use the ESM as a large kinetic impactor, sending it to impact a suitable NEO. ESM has a dry mass seven times larger than the spacecraft used on the successful DART mission.

The ESM currently relies on the Crew Module for several functions including communications, computing, and attitude control sensors; thus, several spacecraft functions would need to be added. Also, ESM mass margins would allow accommodation of a scientific payload, opening the possibility to expand the prime mission for additional science objectives. The concepts considered were divided into augmentation categories of no augmentation (impactors), minimal augmentation (flybys), and low-to-moderate augmentation (orbiters, landers).

The highest priority for each ESM mission is to accomplish the primary mission objectives within the Artemis program. Although the ESM has the potential to deliver additional scientific value beyond its current scope, the scientific value added will have to be weighed against programmatic considerations and carefully analyzed within the ESM's programmatic framework and its stakeholders. Acknowledging this, we explore the possibilities to achieve tantalizing science objectives at a lower-cost.

A mission to NEA (99942) Apophis would provide a unique opportunity to collect and return a regolith sample from a NEA as it passes very close to Earth. ESA is currently investigating the possibility of an orbiter, as part of the RAMSES mission study, to fly close to (99942) Apophis before it makes its closest approach to Earth on Friday, April 13, 2029, with the aim of observing the tidal and magnetospheric effects on the NEA during this close flyby. Later, the asteroid will be well observed by NASA’s OSIRIS-APEX mission. At present, none of these missions or mission studies are investigating the possibility of sample return with a very short duration sample return leg, requiring only a tiny additional momentum to return to Earth. We present the results of a concurrent engineering (CE) study on the feasibility of a sample return capsule based on "now-term technology" available from the space industry named APOphiS SUrface saMpler (APOSSUM). The APOSSUM design assumes to be detached, touch and go with semi-autonomous navigation guidance, actively controlled by thrusters while collecting the regolith matter by means of rotating brushes, and by mid-March 2029 be guided towards Earth at a speed offset of a few tens of meters per second relative to the asteroid. This is orders of magnitude less than the speed required by previous sample return missions due to the very close Earth flyby of (99942) Apophis on April 13, 2029 and the total time needed for return phase is less than a month and the overall mission time is less than a year. The regolith sample contained in the return capsule will arrive on Earth just as the asteroid passes at a safe distance. The spacecraft's entry velocity is about 12.6 km/s, compared to the asteroid's 7.4 km/s flyby, due to Earth's gravitational field. The spacecraft is designed around the entry capsule which, as the sampler, is a mission specific development. The attitude and orbit control systems are based on flight-proven cameras, sensors and propulsion units. The outlined brief sample return mission design scenario is applicable within the design resources to any NEA target asteroid.

Introduction. The Milo Space Science Institute, a nonprofit entity co-founded by Arizona State University (ASU) and Lockheed Martin (LM), in partnership with the University of Colorado at Boulder (CU), aims to conduct a pioneering reconnaissance flyby of (99942) Apophis approximately 1 year before its close approach to Earth in April 2029. The mission, called Apophis Pathfinder, would employ two small satellites comparable to the NASA Janus spacecraft, or potentially repurpose NASA’s two existing Janus spacecraft themselves.
The goals of the Apophis Pathfinder mission are both programmatic and scientific:
A Low Cost, Planetary Defense Reconnaissance Mission to a PHA. The programmatic goals of the mission are to complete the first demonstration of a rapid-response reconnaissance flyby of a PHA to acquire data relevant to Planetary Defense, and to accomplish the mission using a low cost innovative international partnering arrangement. Both the United States National Preparedness Strategy for near-Earth Object Hazards and Planetary Defense and the NASA Planetary Defense Strategy and Action Plan focus on the unique opportunity of the Apophis Earth encounter to advance numerous Planetary Defense goals and objectives. The mission would be a simulation of a planetary defense reconnaissance scenario. Arriving at Apophis ~1 year prior to its close Earth flyby, the mission would determine characteristics that are critical to creating a defense strategy, e.g., a deflection mission like DART. The Apophis Pathfinder mission establishes a low-cost implementation baseline for planetary defense missions using small spacecraft technology piloted by Janus-class smallsat spacecraft.
Scientific Characterization of a Hazardous NEO. Many studies by the planetary science and small bodies communities have advocated for spacecraft missions to exploit the rare, extremely close 2029 Apophis Earth flyby. The 2023–2032 Planetary Science Decadal Survey noted that a “flyby mission to Apophis could be carried out with a SIMPLEx-class mission” and that a “rendezvous well in advance of the Earth flyby could map the asteroid in detail before and after its Earth passage”. Although significant physical changes in the body (except for its spin state) are not expected, this prediction could be tested by scrutinizing the surface for changes in regolith placement and distribution.” The Small Bodies Assessment Group (SBAG) Specific Action Team Report called for flight science investigations “to directly observe a geophysical process, resurfacing due to tidal effects, ... performed by a multi-band high resolution optical-near IR imager on one or more spacecraft near the asteroid before and after the close approach.”
The science objectives of the Apophis Pathfinder mission are focused on the assessment of the shape, geology, and physical, orbital, and rotational parameters of the asteroid prior to its Earth encounter using high-heritage optical and thermal-IR imaging instruments. Specifically, a close flyby of Apophis could provide visible-wavelength images for geologic and topographic assessment and mapping of the sunlit side of the asteroid at scales from ≈1-10 m/pixel, and thermal-IR images of an entire hemisphere for thermophysical properties assessment (e.g., thermal inertia) at scales from ≈10-100 m/pixel. Because the asteroid’s rotation period is ≈30.5 hours, phasing of the two spacecraft flybys by ≈15.25 hours could enable nearly the entire surface to be imaged at optical and IR wavelengths. Such a data set would enable improved derivation of the asteroid’s shape, mapping of the asteroid’s surface morphology, identification of regolith covered regions, and derivation of its pre-Earth-flyby spin state and moments of inertia. The shape and morphology assessments would be critical for enabling the detection of any reconfigurations that have changed its overall structure after the Earth flyby.
Summary. Apophis Pathfinder is an innovative, cost-effective, and non-NASA led flyby mission to Apophis. The mission’s primary objective is to understand the properties and rotation state of the asteroid well before its close approach to Earth. The scientific and Planetary Defense communities can compare the properties and rotation state with data derived from other missions during and after its close approach to measure or infer unique details about the surface and interior of Apophis. The mission’s secondary purpose is to provide data to others ~1 year before the April 2029 Earth encounter, so that missions like ESA’s Ramses and NASA’s OSIRIS-APEX that will encounter Apophis immediately before, during, and after the Earth encounter have ample time to use Apophis Pathfinder initial reconnaissance data to inform mission planning and augment their own scientific and Planetary Defense results.
Apophis Pathfinder also includes a pioneering workforce development and mission implementation approach to Planetary Defense and space science by bringing together emerging universities, research institutes, companies, and space agencies that are seeking relatively low-cost and rapid ways to increase their experience in deep space mission planning, calibration and testing, operations, and science data analysis.

On the 13th of April 2029, Apophis, a 400 meter asteroid, will pass within 31 600 km of Earth’s surface in a retrograde orbit, moving through the magnetosphere and encountering the outer radiation belt, ring current, and outer edges of the plasmasphere. Therefore, this event offers a fantastic opportunity to investigate how small scale airless bodies interact with Earth’s magnetosphere.

The asteroid surface will interact with various particle populations, from cold and dense plasma of the plasmasphere to high energy penetrating particles of the radiation belts. These interactions release ions and neutrals from the outermost layer of Apophis’s surface, revealing its composition and defining the conditions and dynamics of levitating dust, released as a result of surface deformations due to tidal forces. Additionally, these deformations may release volatiles accumulated in the asteroid’s materials, contributing to changes in the asteroid environment.

This paper proposes a CubeSat mission, equipped with high TRL instruments to conduct plasma and neutral gas measurements during the Apophis flyby. The payload will include a mass spectrometer and an ion/electron analyzer, with a total mass under 4 kg, power consumption below 8 W, and telemetry rates under 50 kbps. These parameters align with a 4U CubeSat, which will operate for approximately 3 hours around the asteroid’s closest approach (CA), at less than 1 km from Apophis.

The main focus of this research is the design and optimization of the spacecraft trajectory using a combination of a Weak Stability Boundary (WSB) transfer and a lunar Gravity Assist (GA) maneuver. This approach aims to minimize propulsion requirements while addressing the challenge of catching up to a cis-lunar object in a retrograde orbit from a prograde orbit. Consequently, this could open up opportunities for future rideshare launches to lunar transfer orbits, offering a significant advantage in both cost and flexibility over dedicated launches.

Ion-Beam (IB) deflection is one of three primary mitigation techniques evaluated for use in the 2025 PDC hypothetical asteroid impact exercise. Unlike the other two techniques, Kinetic Impactors (KI) and the use of Nuclear Explosive Devices (NEDs), the ion-beam option is a gentle, slow-push method that, over the course of months to years, can change an asteroid trajectory significantly without the risk of fragmenting or disrupting the body in a possibly unpredictable way. IB deflection is accomplished using a spacecraft equipped with Solar Electric Propulsion (SEP), that carries a large amount of xenon propellant, rendezvouses with the asteroid, positions itself several asteroid diameters away, and orients such that the exhaust beam from one or more of its ion thrusters impinges almost entirely on the asteroid. Each ion thruster is paired with an identical one firing in the opposite direction so that the spacecraft maintains its position relative to the asteroid. Since the ions beam at very high velocity (~70 km/s), a considerable amount of momentum can be imparted over time.

The IB deflection technique offers several advantages over other techniques, in addition to avoiding the risk of unintended or unpredictable fragmentation/disruption. 1) An IB mission can deflect an impact trajectory off the earth equally well in either direction, while a KI mission is generally uni-directional, possibly requiring a much larger deflection. 2) With IB, the momentum imparted to the asteroid should be highly predictable, and not dependent on asteroid properties such as strength, porosity, topography, surface composition, etc. 3) Whereas with KI and possibly also Nuclear, it would be highly desirable to assess size, mass and other properties prior to designing the spacecraft, in order to avoid the possibility of unintended disruption, with IB the spacecraft design could start much earlier, even before the asteroid properties were well known. 4) An IB spacecraft could monitor deflection progress on its own, while for KI a separate rendezvous spacecraft would be required for that purpose. 5) The effectiveness of IB deflection can be amplified via multiple independent spacecraft operating in parallel, whereas such “stacking” of multiple deflections could be much more complex for impulsive mitigation methods.

In this paper we outline our simulations of several realistic ion-beam missions which could successfully deflect the hypothetical PDC25 asteroid over the wide range of masses possible at Epoch 1, and for any impact location along the risk corridor. We consider IB spacecraft with power levels in the 22-80 kW range, using up to three pairs of ion thrusters. We show that for a large subset of possible asteroid masses and possible impact locations, IB offers the only viable non-nuclear method to achieve a successful deflection. If launched early enough, even a modest (22kW) IB spacecraft could deflect the majority of cases. If the asteroid is large and the impact location near the center of the capture disk, however, a single IB spacecraft may not be sufficient, and multiple copies of the spacecraft would be required to operate in parallel to move the trajectory off the Earth.

The atmospheric breakup of an incoming asteroid and deposition of its energy into both the atmosphere and ground is of great interest to the planetary defense community. The breakup of an incoming asteroid will heat the atmosphere and generate a shockwave and is highly dependent on the asteroid’s size, physical characteristics, and incoming trajectory. In this contribution, we analyze how the PDC25 scenario object might fragment in the atmosphere depending on entry angle and asteroid properties. Based on information available at Epoch 1, we examine four different asteroid sizes: 77 m (5th percentile), 127 m (50th percentile), 191 m (95th percentile), and 278 m (100th percentile).
Here we use the SPH code Spheral to perform a parametric study analyzing the amount of energy deposited in the atmosphere by different realizations of the PDC hypothetical threat scenario. We consider three variables: asteroid size, asteroid strength, and incoming angle. Models are run using the open-source smooth particle hydrodynamics code Spheral with the FSISPH solver. Spheral is maintained by Lawrence Livermore National Laboratory, and the formulation used in FSISPH is designed to better model impacts between materials with large discontinuities in properties, such as rock and air. For our parameters, we use the four asteroid diameters described above set forth by the PDC25 scenario. Each tested asteroid is run with an Aba Panu-like strength model and as a fully hydrodynamic object. Aba Panu is relatively strong meteor and is a likely overestimation of asteroid strength and the fully hydrodynamic case, while closer to a rubble pile scenario, is likely an underestimation of asteroid strength. We select three entry angles: a generic 45° case, a near-vertical entry angle associated with an impact point at Cape Town (86.7°), and a shallow case (20°)
Figure 1 summarizes our initial results from our initial 2D analysis. In each case, we find that the fully hydrodynamic bolides break up higher in the atmosphere and have less, if any, intact material that would impact the surface. Similarly, larger bolides remain intact over longer trajectories and are more likely to impact the surface with intact material. Incoming angle also has a notable effect, where a bolide with a shallower incoming angle will tear apart higher in the atmosphere because of the longer travel time needed to reach the surface. Although an incoming angle of 45° is usually assumed for impact studies, these results indicate that the incoming angle has a large influence over the predicted effects and care is needed to accurately determine the location-specific details of a future impact event. Ongoing work will consider these models in 3D and seek to understand the distribution of energy deposition in the atmosphere and ground under the range of possible PDC25 scenarios. These next steps will help us understand how much asteroid energy is converted to threat effects such as blast waves and ground shock after a putative asteroid encounter.

In the PDC25 scenario at initial assessment, the asteroid may impact nearly vertically over Cape Town or at increasingly shallow angles moving north over Africa and Europe. This presentation will compare the predictions for blast and thermal damage from coupled radiation-hydrocode simulations using the ALE3D hydrocode and the NERO thermal radiation transport code.

For height-of-burst blast damage models, the PDC25 scenario is in an interesting size range where different asteroid sizes within that range could cause similar worst-case blast damage depending on their airburst altitude. A more likely smaller asteroid if airbursting near its optimal height of burst can cause similar blast damage to a less likely larger object that hits the ground, below its higher optimal burst height. For evacuation planning and potential damage cost comparison, we will consider the 1 in 1000 risk level, close to a worst case scenario. For both steep and shallow entry scenarios we will examine both large ground impacts and smaller sizes bursting near optimal height.

For thermal radiation damage predictions, hydrocode simulations using the ALE3D hydrocode have been coupled with NASA’s radiation transport code NERO. Previous diffusive approximations of heat transfer are only valid for optically thick and opaque media. NERO calculates in full 3D the spectral line radiation transfer through optically variable materials and is scalable to large domains like these scenarios. This allows calculation of the heat transfer from the hot asteroid entry corridor and fireball after ground impact through cool transparent air to objects on the ground at large distances from the impact. This enables accurate prediction of heat loads on the ground and in particular wildfire ignition. It will also allow calculation of the effective luminous efficiencies, hopefully narrowing the currently wide range of estimates that dominates the uncertainty in estimates of thermal damage. In particular we will compare the luminous efficiencies of ground impacts and airbursts.

Super-bolides are of particular interest to planetary defense since they can release
vast amounts of energy (500 kton to >10 Mton) during atmospheric entry. Superbolides
such as Chelyabinsk (20m, 2013) and Tunguska (50m, 1908) are two
contemporary examples of the effects airburst phenomena have, ranging from minor
structural damage to prominent land devastation. Smaller scale celestial objects
responsible for airbursts exist in greater numbers in our solar system and are
significantly harder to detect. These factors underscore the necessity of developing a
robust understanding of how entry characteristics affect localities and regions on the
ground.

High-fidelity simulations of ground effects, given asteroid properties and entry
characteristics could contribute to this understanding. Unfortunately, the atmospheric
breakup and blast propagation are characterized by different length and time scales,
necessitating separate simulations and an intermediate handoff. We approached this modeling challenge by developing a hydrocode pipeline which consists of two parts,
initialized by explicitly calculating the energy deposition and momentum loss during
the bolide breakup. This deposition is then handed-off into an atmospheric blast
propagation code to estimate ground overpressures and wind speeds.

The airburst is modeled using the FSISPH package of the Smoothed Particle
Hydrodynamics (SPH) code Spheral++. Aspects of the physical problem, such as
entry angle, velocity, geometry, strength, damage, etc., are readily modeled and the
fragmentation and breakup of the asteroid is tabulated as a total energy loss of the
asteroid ‘system.’ This simulation strictly models the airburst event, which lasts several
seconds. The tabulated energy, momentum, and mass change, as a function of
altitude and time, are then utilized as input parameters in the Eulerian blast
propagation code, Miranda. In an Eulerian domain, the airburst ‘zone’ is modeled as
a moving point source with a gaussian distribution of the energy rate at each respective
time-step. This zone is then advanced along the trajectory that the asteroid takes in
space and the blast solver propagates the generated pressure wave to longer end
states.

We apply our new pipeline by utilizing the data generated from a previous SPH
simulation of the Chelyabinsk airburst case. We deposit the tabulated energy, mass,
and momentum within a 3-dimensional cartesian domain within Miranda with complex
ground geometry representative of a realistic landscape, such as an urban setting.
Simulating the Chelyabinsk event via this pipeline allows us to perform a satisfactory
comparison of the estimated to the observed ground overpressures, given some static
set of SPH input parameters based on the literature. Furthermore, informed by the
results of this specific study, we can begin an analysis of how slight variations in the
entry characteristics of a similar scenario, such as entry angle, would affect the
response on the ground.

LLNL-ABS-871533
Prepared by LLNL under Contract DE-AC52-07NA27344.

Please find attached an extended abstract for PDC2025 (9th IAA Planetary Defense Conference).

I am the corresponding author, and can be reached at:
michael.aftosmis@nasa.gov

Asteroid strikes can cause extensive blast damage to surrounding regions, either by impacting the surface or bursting explosively during entry. The severity and extent of the resulting blast damage areas depend both upon the energy of the airburst/impact and the airburst altitude at which most of that energy is deposited into the primary blast. For a given blast energy, there is an ‘optimal’ height of burst (HOB) that produces the largest ground damage extent for a given blast overpressure level. This optimal HOB altitude is much higher for larger energies than it is for smaller energies, and can also be somewhat higher for weaker blast overpressure levels than stronger blast overpressure levels. Below the optimal HOB altitude, the extent of the blast overpressure on the ground can fall off sharply.

These airburst energy-altitude effects are particularly pertinent to the damage estimates for the PDC25 Impact Exercise scenario. In this scenario, the hypothetical asteroid has been constrained to a potential size range and type with estimated airburst altitudes spanning across the associated optimal HOBs, making damage estimates particularly sensitive to the entry conditions and uncertain asteroid properties affecting its breakup. The scenario’s initial impact corridor also has entry angles spanning from nearly vertical to very shallow, and these entry angles substantially affect which sizes burst above, below, or near their optimal burst height at different locations. These variations produce counter-intuitive trends in the blast damage estimates for different asteroid sizes at the different potential impact locations.

In this study, we present airburst and blast damage modeling trends from the Asteroid Threat Assessment Project (ATAP) Probabilistic Asteroid Impact Risk (PAIR) assessment of the PDC25 impact exercise scenario. These results illustrate how asteroid airbursts occurring near their optimal burst heights could cause significantly greater blast damage than much larger surface impacts that release their blast energy far below their respective optimal HOBs. We compare the optimal burst altitudes for the impact energy range of the initial PDC25 case (~3–720 Mt) with the range of burst altitudes modeled for the entry conditions across the initial PDC25 corridor, and show which sizes or properties drive the greatest damage among the resulting combinations of burst energies and altitudes. Demonstrating these nonintuitive damage factors helps identify what asteroid sizes may actually pose the greatest risk when considering mitigation and response options, and helps raise awareness that the largest potential asteroid size is not necessarily the worst-case scenario.

Initial effects of asteroid impact and airbursts include thermal radiation and overpressure blast waves. If sufficiently large asteroid fragments reach the surface, seismic activity or tsunamis may occur if over land or sea, respectively. However, other effects that could extend the geographic areas affected and/or result in long-term physical hazards are less characterized. We categorize these as either downwind or downstream effects. We address the question of when do these effects become non-negligible for the loss of life, ecological damage, and disruption of economic activity.

Keywords: blast, overpressure, Lamb wave, airburst, tsunami

Atmospheric entry and disruption of very large bodies produces blast waves with damage radii reaching hundreds or even thousands of kilometers. Recent 3D computational simulations of large impactors (above roughly 1 Gt kinetic energy at entry) demonstrate that these large blasts initially expand roughly spherically and then transition to more cylindrical behavior as the blast essentially “fills up” the entire height of the atmosphere. Since the blast is constrained by the ground, the large pressure disturbances transition to Lamb waves within the troposphere and can propagate many times around the globe. Over water, these pressure disturbances provide atmospheric forcing of Ocean Coupled Airwaves (OCA) that can cause tidal effects and tsunamis far from the blast source, as recently observed after the 2022 eruption of Hunga Tonga–Hunga Ha’apai [Omira, 2022; Nishikawa, 2022; Ren, 2023].

We present a semi-analytic model connecting the Lamb wave overpressure, blast yield energy, and distance from the blast source following the form of Nishikawa et al. [2022] with an extension to airbursts using the relationship between source energy and Lamb wave period from ReVelle & Whitaker [1996]. We also present a simple trigonometric extension to the wave front propagating around a spherical Earth. Since Lamb waves are essentially cylindrical elastic waves, the large blast model gives overpressure decay rates of $1/r$ rather than spherical blast decay rates of $1/r^2$. This slower blast overpressure decay indicates that blast damage (1 psi or greater) could extend even further than predictions from spherical-blast models or height-of-burst (HoB) models [Glasstone & Dolan, 1977]. Importantly, the Lamb wave model also enables fast and inexpensive estimation of the atmospheric forcing for global tsunami simulation even when the impact point is over land or for landlocked bodies of water.

In addition to the mathematical details of the Lamb wave model, we will show how it connects with weapons-heritage HoB methods near the source. We will also present full 3D simulation results focusing on large asteroids with up to 5 Gt of energy at entry. At these scales, overpressures above 2 psi may extend to over 200 km from the point of impact. The new Lamb wave model fills two modeling gaps: accurately predicting overpressures from large blasts at distances where HoB methods lose accuracy, and providing a tool for driving global tsunami simulations directly from the atmospheric energy deposition of large asteroid entries.

References:
• Omira, R., Ramalho, R.S., Kim, J. et al. “Global Tonga tsunami explained by a fast-moving atmospheric source” Nature 609, 734–740 (2022). https://doi.org/10.1038/s41586-022-04926-4
• Nishikawa, Y., Yamamoto, My., Nakajima, K. et al. “Observation and simulation of atmospheric gravity waves exciting subsequent tsunami along the coastline of Japan after Tonga explosion event.” Sci Rep 12, 22354 (2022). https://doi.org/10.1038/s41598-022-25854-3
• Zhiyuan Ren, Pablo Higuera, Philip Li-Fan Liu, “On Tsunami Waves induced by Atmospheric Pressure Shock Waves after the 2022 Hunga Tonga-Hunga Ha'apai Volcano Eruption” JGR Oceans 128(4), 12 April 2023, https://doi.org/10.1029/2022JC019166
• D.O. ReVelle, R.W. Whitaker, “Lamb waves from airborne explosion sources: Viscous effects and comparisons to ducted acoustic arrivals.” LANL Report, LA-UR-96-3594, Dec. 1996
• S. Glasstone, P.J. Dolan, The Effects of Nuclear Weapons, third ed., United States Department of Defense and the Energy Research and Development Administration, 1977. http://www.fourmilab.ch/etexts/www/effects/

Meteorite terrestrial impacts are established as the causes of large circular geological structures, major crustal deformations, large volumes of displaced rocks, extensive ejecta, and ultimately non-ideal debris cloud formation. Statistically, these are rare events, and the physical processes involved in terrestrial impacts and their subsequent induced effects, such as cratering, ejecta formation, airborne debris cloud formation, seismic ground motions, and eventual tsunami generation if impacts are shallow water seas, are very complex, and a physics-based approach is essential to differentiate between the different physical and mechanical processes and to address the key parameters that drive their behaviors and their implication on scaling laws. In the present study, we rely not only on HPC numerical simulations but also on the expertise acquired from of high energy near-surface explosions. Results presented in this paper indicate a slightly shallower or, depending on the geology, greater depth of analogue burst explosions is required to mimic scaling laws of crater diameter, displaced mass, ejecta blanket formation, and the characteristic times for crater-induced ground motions such as peak-particle velocities and accelerations. Crater debris depth and ejecta-travel distances are also numerically investigated because they play the key source parameters of cloud formation and global circulation. Numerical results show with confirmed confidence using existing observation data that the variations within the ejecta velocities are more consistent with half shallow buried yield-dependent high-explosive cratering events which is counter-intuitive to the common-wisdom assumptions. We supplement the results with meteorite impact movies on different crustal emplacements & geologies.
Lawrence Livermore National Laboratory is operated by Lawrence Livermore National Security, LLC, for the U.S. Department of Energy, National Nuclear Security Administration under Contract DE-AC52- 07NA27344.

This paper builds on the 2024 developments within SMPAG and my recently published arguments in Acta Astronautica and Nature Communications. It offers the scientific community and SMPAG delegates a comprehensive roadmap aimed at fostering cooperation in the event of an asteroid being detected on a collision course. The proposed approach seeks to mitigate the challenges typically posed by collective action problems in the global governance of a shared security threat through the establishment of a multilateral planetary defense (PD) security regime.
Firstly, the paper outlines the desirable ideal state of the regime, which is grounded in the common principles of multilateral cooperation: indivisibility and diffuse reciprocity. In this context, a regime is understood as a set of rules, norms, principles, and decision-making procedures that facilitate sustainable and mutually beneficial cooperation among states. The principle of indivisibility ensures that all member states receive equal assurances of security, regardless of the size of their contributions. Meanwhile, the principle of diffuse reciprocity is realized through the willingness of states to contribute their capabilities unequally. This approach allows smaller states to benefit from the security provided by the broader community, even if their individual contributions are relatively modest. At the same time, it grants powerful states the legitimacy to employ even stigmatized technologies, such as nuclear explosive devices (NED), as the regime ensures the international community a necessary level of predictability regarding the actions of all actors.
Secondly, the paper proposes various next steps for the international community to reach the ideal state of the regime. 1) Along with technical procedures, any regime includes decision-making procedures designed to prevent sudden unpredictable decisions by decision-makers who did not participate in the development of the regime – a task for SMPAG. 2) UN General Assembly resolutions lack binding authority but possess significant normative power. A resolution focused on establishing the norm of "Responsibility to Defend Earth" could enhance cooperation by aligning the cognitive perceptions of national delegations on planetary defense – a task for national delegations. 3) Drafting the treaty might not result in its formal entry into force, but it could serve to systematize and coordinate diverse national positions, ultimately shaping the most acceptable regime, which could later be adopted as a recommended non-binding framework for guidance, which would still help coordination – task for SMPAG.
If the scientific part of the planetary defense (PD) community strengthens its argument for the necessity of nuclear explosive devices (NEDs), the only viable approach to challenge the Cold War-era nuclear disarmament legal framework is to construct a new regime specifically tailored to this global security issue. If NEDs remain the sole technology capable of preventing even a localized disaster, the international community must reach a common understanding on the rationale behind their use (norms and principles) and establish a predictable legal framework (rules and procedures). This approach ensures that decisions are guided by a legitimate, collectively agreed-upon regime rather than unilateral declarations by powerful states asserting their readiness to act if requested by those within the risk corridor.

Planetary defense, the protection of Earth from hazardous Near-Earth Objects (NEOs) such as asteroids and comets, has emerged as a critical interdisciplinary challenge that intersects space technology, international law, and global cooperation. Current frameworks like the Outer Space Treaty (1967) \cite{dembling1967evolution} and its associated conventions establish principles for the peaceful use of space but offer limited guidance on issues specific to planetary defense. Key challenges include jurisdictional authority over deflection missions, liability for unintended consequences, and compliance with the treaty’s non-appropriation principle when utilizing deflected asteroid resources. The lack of a robust governance mechanism heightens the risk of unilateral actions or inequitable participation in planetary defense initiatives.

National and regional efforts, including NASA’s Planetary Defense Coordination Office and ESA’s Space Safety Program, have made significant strides in NEO detection and mitigation. However, the global nature of the threat demands a more cohesive and inclusive framework. This includes expanding the role of international organizations such as the UN Office for Outer Space Affairs (UNOOSA) and leveraging existing mechanisms like the International Asteroid Warning Network (IAWN) and the Space Mission Planning Advisory Group (SMPAG). Private actors, including SpaceX and Blue Origin, are poised to contribute technological solutions but require appropriate regulatory oversight to ensure alignment with global interests.

To address these gaps, this work advocates for a dedicated planetary defense treaty or enhanced protocols within the Outer Space Treaty, emphasizing transparent data sharing, equitable resource allocation, and clear liability frameworks. A funding model that engages both spacefaring and non-spacefaring nations is essential, as is a commitment to public engagement to ensure societal readiness for planetary defense measures. By integrating policy, law, technology, and public outreach, this research aims to outline a governance model that prioritizes ethical responsibility and global cooperation in safeguarding humanity’s future.

Most efforts to look at Planetary Defense have only considered protecting the Earth. But there are now concrete plans to establish human settlements and other significant infrastructure on the surface of the Moon over the course of the next several decades. This puts the people – and strategic assets – there at risk from asteroid impacts.

The past several decades have seen our species make great strides in our ability to protect our home planet from impacts of asteroids and comets. At the same time, mankind has also started to expand its sphere of influence and interests into space, and it is appropriate now to consider widening the sphere of vigilance and protection. The upcoming conjunction between Earth and the asteroid Apophis in April 2029 illustrates this threat, since simulations show that Apophis will not just pass closely by Earth, but also closely by the Moon.

While major impacts both on Earth and on the Moon are rare, Earth’s atmosphere protects it from the impact of the much more frequent smaller objects. The Moon lacks this natural shield, and thus potentially damaging impacts can be expected to happen much more frequently.

Furthermore, due to the Moon’s lower gravity field and again due to its lack of atmosphere, even smaller impacts can generate ejecta that can make it into cislunar space and threaten people and infrastructure there.

At the same time, habitats and other structures on and around the Moon will likely be less resilient than terrestrial structures, and thus more vulnerable to direct impacts and related second-order effects such as Moonquakes. Evacuations on the Moon will be more challenging as well compared to Earth.

Finally, combining Lunar exploration with Planetary Defense efforts could create another fruitful area of international collaboration, with geostrategic benefits.

This paper will therefore explore whether or not our planetary defense umbrella should be expanded to include cislunar space, and how this could be achieved.

Abstract
The main aim of planetary defense is to keep Earth safe from any possible asteroid collision which is an essential component of space exploration. The particular issue of liability can be raised by conducting such missions while the existing international legal framework lacks any such treaty, laws, rules, or regulations regarding liability from planetary defense missions. This paper analyses the legal consequences of planetary defense missions while emphasizing the necessity for a comprehensive liability framework to address risks related to such missions. The analysis begins with examination of current treaties specifically the Outer Space Treaty of 1967 and the Liability Convention to assess their applicability to planetary defense missions. As these frameworks offer some guidance but they inadequately address various issues related to the possibility of collateral damage and asteroid deflection technologies.
International cooperation is necessary to manage liability effectively because of the global nature of planetary defense. Taking into account spacefaring nations and international organizations such as the UN can coordinate efforts to control risk and assure shared responsibility. The role of international collaboration in liability management is examined in this study. Furthermore, it argues that strengthening international cooperation is important to both the fair and equitable distribution of liability and to the success of planetary defense missions.
Private space companies are the center of growing concern in planetary defense such as SpaceX and Blue Origin, it's just two of them. The question of liability for damages caused by the activities of private space entities become very important because of the increasing engagement of private space entities in space missions. The legal and regulatory issues related to private space sector participation in planetary defense are discussed in this paper. While promoting clear liability that outline the obligation of both private and government entities.
The study concludes by proposing legal reforms in order to adjust current space law to the needs of planetary defense. In order to make sure that clear and comprehensive liability rules and regulations are in place. It promotes the development of an international protocol that addresses liability, particularly for planetary defense missions. This study aimed to contribute to the creation of a more comprehensive legal framework for planetary defense by pointing out weaknesses in the existing legal framework and providing practical solutions. it will defend Earth from asteroid threats because it will enable safe, responsible, and cooperative international efforts.

Deflecting a hazardous near-Earth object (NEO) away from Earth impact may be done using a variety of techniques. Deflections may be categorized according to whether they are designed to be accomplished, in principle, with a single action, or whether they are designed to require multiple actions spread across time.

An NEO might be deflected with a single kinetic impactor (KI) or a single standoff detonation of a nuclear explosive device (NED). Such single-action deflection is possible when the nature of the NEO’s orbit, the amount of warning time, and the NEO’s mass and strength are all such that 1) a single KI or NED is sufficient to give the NEO the velocity change (delta velocity or DV) required for deflection, and 2) the NEO’s mass and/or strength enable it to tolerate that amount of DV without unwanted fragmentation. If those criteria are not met, then a series of smaller DVs may be imparted to the NEO such that their total effect eventually deflects the NEO. There may be some weeks or months in between the applications of those multiple deflection DVs for various reasons, including allowing time to assess the effects of the previous deflection DV, and launch limitations. Such a multi-action KI or NED deflection campaign could span months or even years.

KIs and NEDs are examples of impulsive, or “fast push” deflection techniques that change the NEO’s velocity instantaneously. By contrast, “slow push/pull” deflection techniques apply a very small continuous acceleration to the NEO over a long period of time to accomplish the total deflection of the NEO. Such techniques include the gravity tractor (GT) and ion beam (IB) deflection. Their small accelerations typically require years or even decades to fully deflect an NEO.

Any multi-action deflection (impulsive or slow push/pull) gradually moves the NEO, in a premeditated manner, away from its original natural Earth impact location. This necessarily, in effect, aims the NEO at locations not originally directly threatened by the NEO, as part of the gradual process of fully deflecting the NEO. The newly threatened locations would be known in advance. Should the deflection mission campaign fail to complete the deflection for some reason, then the NEO and all of its destructive energy will be heading towards a particular location that was not originally naturally threatened—and the new location now threatened would have been known in advance rather than unpredictable.

In this paper we present an analysis of the legal and policy issues pertaining to multi-action NEO deflection, considering both impulsive and slow push/pull. Our analysis considers existing bodies of law and treaties, existing legal precedents and analyses, the motivations and intentions of the launching state(s), whether the launching state(s) had a single-action deflection or disruption option available (even if nuclear) but selected a multi-action deflection option anyhow for some reason(s), and more. Findings and conclusions will be discussed, aiming towards articulating an effective and appropriate legal framework for proper handling of multi-action NEO deflection options prior to being confronted with an actual emergency.

Theoretical studies have considered use of nuclear explosive devices (NEDs) to deflect hazardous near-Earth objects (NEOs) for decades. Questions about how this would work in international relations, especially with respect to the Outer Space Treaty and the Partial Test Ban Treaty, have lingered though—making policy planning and international discussions difficult. Many discussions conclude that if an actual NEO deflection scenario arose, the decision to use a NED would hinge on the specifics of the situation and likely require endorsement by the United Nations Security Council.

This paper offers a possible set of international protocols for employing NEDs to deflect a hazardous asteroid. We begin by summarizing previous analyses of NED use for planetary defense, highlighting what technical studies have shown up to the present. We then propose protocols that incorporate technical, operational, and diplomatic elements. These include approaches to multilateral coordination involving the UN Security Council, design and trajectory factors to meet safety and transparency requirements, and diplomatic commitments to preserve future space and nuclear security.

We develop these protocols both as a future reference and to help facilitate new technical and international discussions, and we invite continued improvement. Ultimately, these preliminary NED planetary defense protocols could facilitate transparent planning for NEDs as part of new planetary defense strategies and capabilities.

The views in this abstract and paper are solely those of the authors, and do not necessarily reflect the official policy position or views of the U.S. government.

Keywords: planetary defence, nuclear weapons,NPT, legality

Numerous so-called asteroid impact mitigation techniques have been and continue to be discussed. The range of proposed measures goes from gravity tractors to destruction or deflection of asteroids through nuclear explosions.
Especially when faced with very large objects and only a short warning time, the latter option – namely the nuclear one – might be one of the few feasible options.

But the deployment of nuclear explosive devices to counter incoming NEOs faces several legal questions. International law has certain reservations against nuclear weapons in space. The 1967 Outer Space Treaty forbids to station nuclear weapons or other weapons of mass destruction in Earth orbit, on the Moon or other celestial bodies or otherwise in outer space. Further, the Partial Test Ban Treaty forbids nuclear test explosions in space. Now, it can be argued that nuclear explosives used for planetary defence are not weapons and that an operational planetary defence mission is not a test. But the wording of the NPT applies to nuclear weapons tests and to “any other nuclear explosion.”
Yet, from historical, legal and political perspectives, several arguments can be made that such an operation would still be legal. A further look will be given at options to create more legal clarity

Keywords: Impact Effects, Political, Legal, Social and Economic Consequences, United Nations.

Abstract
The virtual object of the 2025 PDC exercise assumes an asteroid of about 200 Meters diameter, approaching Earth at 14 km/s with a possible impact in 2041. The risk corridor is a north-south line from northeastern Europe across the Mediterranean, the Sahara, and central Africa towards South Africa. Even though the exercise assumes that attempts will be made to deflect 2024PDC25, the probability of an impact at some point in the risk corridor remains. It is evident that a threat of this nature will have serious consequences, starting several years before the actual
event.