Speaker
Description
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).