BIRDY - Planetary Geodesy of Small Bodies _through CubeSats in Autonomous Navigation

International audienceBringing a CubeSat that could autonomously navigate in the vicinity of small bodies would be an ideal platform to perform radio-science from multiple locations at low altitudes that are too risky for a mothercraft. The perturbations due to the asteroid during the orbit or multiple flybys of the CubeSat allow the reconstruction of its detailed gravitational field by planetary geodesy and, eventually, the identification of its internal structure. To this purpose, we are developing the BIRDY concept of interplanetary CubeSat, accompanying a mothercraft for planetary geodesy of small bodies (asteroids, comets, satellites). Besides, classical radio tracking can be coupled to other techniques such as space astrometry and VLBI [1]. Interplanetary CubeSats need to overcome a few challenges before reaching successfully their deep-space objectives: link to ground-segment, energy supply, protection against radiation, etc. Besides, the Birdy CubeSat - as our basis concept - is designed to be accompanying a mothercraft, and relies partly on the main mission for reaching the target, as well as on data-link with the Earth. Autonomous navigation could then provide a way to perform a new kind of planetary geodesy, particularly well adapted to small bodies..Future mission for space exploration or sample return could hence take profit of having accompanying nano-orbiters, as complementary or deported instruments with increased autonomy. Furthermore, in the current context of more and more small satellites being launched in solo or in network/swarms missions, the operational cost of such projects is booming; especially because of the required ground segment. This kind of technology could greatly increase the feasibility of such projects (by moving the decision making to the satellite), for example high frequency imaging of the Earth, Radio Interferometry from space, simultaneous multi-point in situ study of the solar wind, etc. A performant autonomous navigation function for small satellite could hence unlock new scientific missions and commercial applications.This autonomous attitude and orbit determination and control function (a.k.a autonomous navigation) for small satellites, in addition to radio science fro planetary missions, is currently being developed by a Consortium made of laboratories LESIA and IMCCE from Observatory of Paris in France, and the National Cheng Kung University and ODYSSEUS Space Co., Ltd in Taiwan. Before going to deep-space, and performing planetary science, our project will start with BIRDY-1 orbiting the Earth, to validate the concepts of adopted propulsion, IFOD and orbit maintenance, as well as the radio-science.[1] Gurvits, L. et al. 2013. Planetary Radio Interferometry and Doppler Experiment (PRIDE) for the JUICE mission. EPSC 8, 357.This work has been supported by Labex ESEP (ANR N° 2011-LABX-030