Abstract: In an antenna system for tracking a satellite, a prediction of the angular orientation of the satellite relative to the antenna as a function of time is obtained from the orbital parameters of the satellite. The mechanisms for controlling the angular position of the entire antenna structure then "drive" the entire structure so as to point the antenna beam towards the predicted position of the satellite as the satellite progresses in its orbit. The "drive" instructions are perturbed slightly so as to cause the antenna beam to "dither" slowly about the predicted satellite positions. The variations in signal strength produced by the dither are then used to determine the azimuth and elevation errors. The orbital parameters upon which the predictions are based are then adjusted so as to minimize the observed azimuthal and elevation errors. Because any error in the orbital parameters changes only very slowly, a relatively slow "dither" and a long time constant can be used in the correction process.