Adaptive Alignment of a Shipboard Satellite Terminal

Shipboard satellite antennas are limited in open-loop pointing accuracy by alignment errors in installation. If the error values could be found, pointing accuracy could be improved by adding correction terms to the equations used by the control processor in performing platform stabilization. The standard autotrack loops for low SNR links have very narrow bandwidths, making them too slow to track out time-varying pointing errors induced by the platform motion. We have developed a new algorithm based on an optimal estimator to perform both satellite tracking and estimation of ephemeris and alignment errors from satellite tracking data. The primary benefit of this algorithm is better terminal performance due to improved pointing and tracking accuracy. Other potential benefits include: reduced antenna system installation costs; automatic realignment of antenna components replaced at sea; antenna system design simplification; and reduced target acquisition time.