Initial SPHERES Operations Aboard the International Space Station

Abstract

The Satellite Position Hold Engage Reorient Experimental Satellites(SPHERES) program, developed by the MIT Space Systems Laboratory,began operations aboard the International Space Station (ISS) on May2006. SPHERES was designed as a research facility to demonstratemetrology, control, and autonomy algorithms for distributedsatellites systems. By operating in the risk-tolerant environment ofthe ISS, SPHERES allows researchers to push the limits of theiralgorithms. Five test sessions, conducted during 2006, achievedmultiple objectives for the different areas under study. The firsttest session was dedicated to hardware checkout. The second testsession demonstrated basic 6DOF closed-loop control of thesatellites. Fault detection and isolation algorithms were alsotested, successfully using the inertial measurement system to detectsimulated faults in space. Formation flight tests during the fourthand fifth session demonstrated two types of control architectures.Following the principle of incremental algorithm development,demonstrations of multiple scenarios of spacecraft docking occurredduring test sessions one through four; the last session demonstrateddocking to a tumbling spacecraft. The results of these test sessionsare the basis upon which substantial more research will be conductedin the following years.