Gravity-gradient stabilization for a spinning satellite with despun line of sight

Abstract

A spin-stabilized cylindrical satellite is suspended either magnetically or electrostatically from a gravity-gradient-stabilized reflector that directs a pencil beam of radiation emanating axially from the satellite toward the earth. Solutions for the motion of a gravity-gradient boom with reference to the local vertical are obtained. The dynamics of the satellite combining spin stabilization with gravity-gradient stabilization result in a stable system with a fixed nutation frequency that can be made high by design. Vibrations in the roll and yaw axes are easily damped by a nutation damper in the spinning cylinder. Damping of the pitch vibration of the reflector can be obtained with a single, cold-gas, pulsed jet that also can be used to prevent angular velocity decay of the spinning cylinder and to control the orbital period for station-keeping. The system described is basically passive as far as the control torques are concerned; however, active means are used to damp pitch vibrations of the nonspinning reflector. Thus, this system can achieve high accuracy of stabilization, in addition to the advantages of high reliability.