Evaluation of autonomous guidance techniques for space rendezvous and withdrawal strategy

Future space missions like planetary samples return, formation ying and interferometry systems, in-orbit assembly and servicing concepts; call for mastering the rendezvous problem: bringing a spacecraft to a given relative state with respect to a target in a given duration at a minimal cost. The complexity of the envisioned missions, and the risk of collision between the vehicles involved, call for a high level of autonomy (no ground control or planning) and robustness (automatic elaboration of withdrawal strategy) of the rendezvous system. From an operational point of view, rendezvous on any type of orbit shall be possible: while circular orbits are the most frequent ones, eccentric orbits could be considered in certain cases or as backup if a failure arise. In this context, the French Space Agency (CNES) has nanced a study whose goal was to assess several autonomous guidance techniques for rendezvous and formation ying on circular and elliptical orbits. An extensive literature review has been performed on relative motion modelling and stability conditions: withdrawal or standby strategy could indeed bene t from naturally bounded relative motion. Several conditions have thus been tested against perturbations and inight conditions. Di erent guidance solutions have also been reviewed: analytical methods, optimisation methods, and optimal control techniques. Two algorithms have been benchmarked: analytical guidance and direct optimisation guidance based on xed manoeuvre times; and their performances (precision, consumption, computational load and robustness) have been evaluated on several test cases covering a wide range of rendezvous types on di erent orbits.