Estimation of orbital states of a satellite

Recently, the research in the area of search and rescue satellite-aided tracking (SARSAT) has gained great impetus. The efficiency of the search and rescue program depends, among other factors, on the accuracy of the position information of the distressed platform, e.g., a downed aircraft. This in turn depends on the accuracy of the estimate of the SARSAT satellite's orbital position. In the present work, an extended Kalman filter and UD-filters are used to estimate the orbital position of a SARSAT satellite. The effect of two sets of observables and of certain a priori statistics on the position and velocity estimates are studied. Altman's (1972) unified state model is used for the orbital trajectory dynamics, and angles and range are used as observables. The results of the comparison of four orbit estimators are presented for simulated data obtainable from a ground-based observation site.