Tracking systems for satellite communications

Satellites in nominally geostationary orbits possess diurnal motion which causes the apparent position of the spacecraft to wander in the sky as seen by an earth station. If uncompensated this causes a variation in the performance of the communications link. The motion of the satellite therefore has to be tracked by the earth station antenna. During the past twenty years or so a considerable amount of work has gone into the development of tracking schemes for satellite communication systems. A review of the various techniques is presented. For each method used the principle of operation is described and the various salient features extracted. Comparisons are made where appropriate and practical implementations of the systems discussed. The application of intelligent control algorithms to tracking is also considered. The areas covered include, orbit determination, optimal estimation techniques, performance, and practical implementations. Recently introduced techniques are considered and likely future developments projected.