An Algorithm for Autonomous Longitude and Eccentricity Control for Geostationary Spacecraft

In order to lower the cost of maintaining satellites in orbit, spacecraft designers are seeking flight software that provides more autonomy. Longitude and eccentricity are good candidates for autonomous control with geostationary spacecraft. The algorithm presented in this paper couples longitude control with eccentricity control. Longitude drift is modeled in one dimension and controlled with a quadratic equation predicting the spacecraft Earth reference longitude after a predetermined amount of time. After the basic longitude control algorithm was written, a differential corrections scheme was added resulting in an improved longitude error of +/- 0.015 degrees longitude. Finally, longitude control and two-part maneuvers for eccentricity control were implemented. The result is good longitude control and eccentricity control to the desired mission constraints