SPACECRAFT CONTROL-SYSTEM FOR THE RELATIVITY MISSION

The attitude and translation control system described in this paper pr ovides precision pointing and drag-free control to accomplish a scient ific mission. The unique proportional helium thruster, which uses heli um boiloff from the payload, controls thrust using pressure feedback t o meet the high-accuracy requirements for force knowledge. The attitud e control law torque commands are combined with the translation contro l law force commands through a distribution matrix to determine indivi dual thruster commands. The Global Positioning System (GPS) is used to determine position and velocity.