Speakers
Description
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.