Comparison of Two Error-Space Estimate Method for Space-Earth Optical Communication

Acquisition, Tracking and Pointing (ATP) is important in free space optical communication. For mobile ground terminal of space-earth communication especially, real time state estimation and prediction of the satellite with high accuracy is necessary to improve precision and stability of ATP system. When error-space estimate method is used for state estimation, the motion of satellite is separated into original guide data and guide error to reduce maneuver level, and estimated in state space and error space respectively and constituted high accurate state estimation to guide the gimbal of ground terminal steadily and accurately. Two conditions of the method are discussed and compared where the satellite is considered as two kinds of generalized synergic target. In first condition, last measurement of satellite state is regarded as original guide data and the satellite is regarded as maneuver target. In second condition, offline estimation of the satellite according to kinetics is regarded as original guide data. Experiment results show that the satellite state estimation of second condition is with higher accuracy than that of first condition, and estimation error increases more slowly along with prediction steps.