Active Magnetic Control System for Gravity Gradient Stabilized Spacecraft

Active magnetic control is studied as a means to improve the capabilities and perfonnance of gravity gradient stabilized spacecraft. Active magnetic control eliminates the need for a passive damper and can reduce significantly the costs and complexity of other functional parts of the spacecraft. The system under study includes three magnetic torquers, one three-axis magnetometer, and a control processor. It does not require any moving parts, and provides for rapid libration damping. tighter stabilization and active control of the yaw angle. Control algorithms are defmed. Results of the analysis of the control laws and computer simulations, including high-order models of the geomagnetic field and atmospheric disturbance torques, are presented. The algorithms perfonn well within a wide range of orbital inclinations and attitude angles and allow maneuverability and stabilization aroWld the yaw axis. A Kalman Filter is used to provide estimates of the attitude angles, the angular rates, and a global disturbance torque, based on measurements from the magnetometer. Results of simulations, including the attitude estimator in the control loop, are presented. The possibility of a fully autonomous acquisition, deployment, and stabilization sequence using the magnetic control system is discussed.