Orbit acquisition, rendezvous, and docking with a noncooperative capsule in a Mars sample return mission

The Mars sample return mission is intended to perform autonomous rendezvous and docking, aimed at gathering Mars samples, stored in an orbiting capsule. This study focuses on guidance and control techniques for the three phases of a typical Mars sample return mission: (i) orbit acquisition, (ii) phasing and correction maneuvers, and (iii) rendezvous and docking with the orbiting sample (OS) capsule, which is assumed to be a noncooperative spacecraft. The chaser vehicle is assumed to be equipped with both chemical and electrical propulsion. The latter is used in phase (i), in conjunction with nonlinear orbit control. This can be regarded as an autonomous guidance technique also in the presence of nonnominal flight conditions. In phase (ii), a phasing strategy and proper correction maneuvers are designed, to reach suitable parking conditions, identified through the orbital commensurability criterion. Then, a guidance, control, and actuation architecture is proposed for phase (iii), split in arc 1 (proximity maneuvers) and arc 2 (final approach and docking). Feedback linearization is employed for trajectory control, aimed at tracking a reference path, which is iteratively defined from the estimation of the rotational state of the capsule. Two distinct, nonlinear feedback control laws, enjoying quasi-global stability properties, are used for attitude control. Actuation is demanded to a pyramidal array of single-gimbal control momentum gyros, the main thruster, and an arrangement of side thrusters. A large set of perturbations (including navigation and actuation errors) are modeled. Monte Carlo simulations prove that the guidance, control, and actuation architecture at hand is effective to complete safe docking with a noncooperative OS capsule.