On Active Attitude Control of Satellites

Three phases of active attitude control of an orbiting satellite are examined: the despinning mode, the reorientation mode, and the control mode. Each of these modes is considered in the light of requirements for long-life mission, where the ratio of control torque to satellite inertia must be minimized. Investigations of the minimum amount of information necessary for a gravitationally stabilized satellite are also included. It is shown that yaw information may be dispensed with in many cases. The paper also includes a discussion of a novel method of providing controlled damping of a gravitationally stabilized satellite by means of internal moving parts and frictional dissipation involving feedback. Some numerical results are given.