Flight Testing of Multiple-Spacecraft Control on SPHERES During Close-Proximity Operations

A multiple-spacecraft close-proximity control algorithm was implemented and tested with the Synchronized Position Hold Engage and Reorient Experimental Satellites (SPHERES) facility onboard the International Space Station. During flight testing, a chaser satellite successfully approached a virtual target satellite while avoiding collision with a virtual obstacle satellite. This research contributes to the control of multiple spacecraft for emerging missions, which may require simultaneous gathering, rendezvous, and docking. The unique control algorithm was developed at the U.S. Naval Postgraduate School and integrated onto the Massachusetts Institute of Technology's SPHERES facility. The control algorithm implemented combines the efficiency of the linear quadratic regulator (used for attraction toward goal positions) and the robust collision-avoidance capability of the artificial potential field method (used for repulsion from moving obstacles). The amalgamation of these two control methods into a multiple-spacecraft close-proximity control algorithm yielded promising results, as demonstrated by simulations. Comprehensive simulation evaluation enabled implementation and ground testing of the spacecraft control algorithm on the SPHERES facility. Successful ground testing led to the execution of flight experiments onboard the International Space Station, which demonstrated the proposed algorithm in a microgravity environment.