SATELLITE ACTIVE MOTION DAMPING

Methods and apparatus are provided for active motion damping of a spacecraft whose attitude control system (SACS) has experienced a partial failure. In a preferred embodiment, the apparatus comprises, an attitude control processor (ACP), a motion damping controller (MDC) coupled to the ACP, a control moment gyro (CMG) comprising a gimbal loop controller (GLC) coupled to the MDC and a gimbal motor with input coupled to the GLC and gyroscopic torque output coupled to the satellite. Normally, a gimbal rate command (GRC) from the ACP passes to the GLC for execution to rotate the CMG gimbal and the coupled satellite. If the ACP output becomes invalid, the MDC assumes control and can modify CMG operation in several ways to safely decelerate a moving satellite without hazardous mechanical stress. Following such active motion damping, the CMG remains quiescent until a RESET is received whereby further valid GRCs are then executable.