A method of earth-pointing attitude control for elliptic orbits

Abstract

A method of attitude control utilizing active regulation of the satellite pitch moment of inertia for controlling a non spinning satellite in an elliptic orbit to an Earth-pointing orientation is investigated. The moment of inertia regulation is prescribed by an open-loop control function in combination with a feedback control which is proportional to pitch attitude error. The open-loop inertia regulation maintains an Earth-pointing pitch equilibrium, and the feedback regulation controls disturbances from the equilibrium. Roll-yaw attitude error is controlled in a semiactive manner through the use of a damped, gimballed pitch rotor. Stability investigations made through the use of Floquet theory show that an asymptotically stable Earth-pointing attitude can be obtained with the method of control for eccentricities ranging from 0 to 0.95. Control system time constants and sensitivity to eccentricity error are also studied. © 1972 American Institute of Aeronautics and Astronautics, Inc. All rights reserved.