ANTENNA SERVO DESIGN FOR TRACKING LOW-EARTH-ORBITING SATELLITES

The upcoming NASA missions will require tracking of low-orbit satellites. As a consequence, NASA antennas will be required to track satellites at higher rates than for the current deep-space missions. This paper investigates servo design issues for the 34-m beam-waveguide antennas that track low-orbit satellites. This includes upgrading the servo with a feedforward loop, monopulse controller design, and tracking error reduction either through proper choice of elevation pinion location or through application of a notch filter or adjustment of the elevation drive amplifier gain, Finally, improvement of the signal-to-noise ratio through averaging of the oversampled monopulse signal is described.