Didymos Gravity Science through Juventas Satellite-to-Satellite Doppler Tracking

Juventas is a 6U CubeSat designed as part of ESA's Hera mission to provide bonus science. Hera is a candidate ESA mission that will be humankind's first probe to rendezvous with a binary asteroid system. Hera is ESA's contribution to an international collaboration project named Asteroid Impact and Deflection Assessment (AIDA). NASA will first perform a kinetic impact on Didymos secondary, nicknamed Didymoon, then Hera will follow-up with a detailed post-impact survey, to fully characterize this planetary defense technique. The CubeSats will be deployed by the Hera spacecraft once the Early Characterization Phase has completed. In close orbit within the Didymos system, Juventas will carry out satellite-to-satellite Doppler tracking to measure the asteroid gravity field and will complete a low-frequency radar survey, to unveil Didymoon interior. This paper describes the mission scenario for the gravity science experiments to be carried out by Juventas, together with the techniques building on the optical combination of previous radio science studies carried out in the context of ESA's AIM (Asteroid Impact Mission) studies. Finally our results and achievable accuracy for the estimation of the mass and gravity field of Didymos primary and secondary are presented.