Algorithm for Autonomous Longitude and Eccentricity Control for Geostationary Spacecraft

To lower satellite orbital maintenance cost, spacecraft designers are seeking flight software that provides more autonomy. Longitude and eccentricity are good candidates for autonomous control of geostationary spacecraft. The algorithm presented couples longitude control with eccentricity control. Longitude drift is modeled as one-degree-of-freedom motion and controlled with a quadratic equation predicting the subspacecraft Earth reference longitude after a predetermined amount of time. After formulation of the basic longitude control algorithm, addition of a differential corrections scheme resulted in an improved longitude error of ± 0.015 longitude. Finally, implementation of longitude control and two-part maneuvers for eccentricity control successfully met the desired mission constraints. The algorithms developed form the basis for preparation of flight software for a geostationary spacecraft scheduled to launch in the next few years