JuRa: the Juventas Radar on Hera to fathom Dimorphos

In 2022, DART/NASA will impact Dimorphos to quantify the mechanical response of the moonlet, mainly from ground-based observation. Five years later, HERA/ESA will be a unique opportunity to deeply investigate the Didymos system to better constrain mechanical models. Onboard Juventas, one of the small platforms carried by HERA, the Juventas Radar -JuRa- will fathom Didymoon and provide the first direct observation of an asteroid deep interior: Information about the internal structure is crucial for science, planetary defense and exploration since our current knowledge relies entirely on inferences from remote sensing observations of the surface and theoretical modeling.

JuRa is a monostatic radar at 60MHz carrier frequency and 20MHz bandwidth. Its flight model will be delivered beginning of 2023. Its first objective is to characterize the moonlet's interior, to identify internal geological structure such as layers, voids, sub-aggregate, to bring out the aggregate structure and to characterize its constituent blocks in terms of size distribution.

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. Radar bypasses the near surface alteration by space-weathering and thermal-cycling as observed with optical remote sensing.

The same characterization applied to the main asteroid of the binary system is among the secondary objectives, to detect differences in texture and composition and to support the modeling of the binary system's formation.

Thus, the observation of the structure and composition of moonlet will provide constraints on the mechanical model of the impact process. Comparing the observations of the moonlet and the main body, it will constraint the model of binary system formation to discriminate between progressive versus catastrophic process and more generally on the stability condition of the system.

In this talk, we will review the JuRa science objectives and the instrument status showing the test results and the instrument performances. Then we will present the proposed operation strategy and the developed approaches for data processing.