Reducing selective availability effects on post-processed orbits for satellites with limited gps telemetry

摘要

Many current satellite missions are using GPS for navigation solutions. Some missions are reducing receiver complexity by transmitting telemetry limited to receiver position and velocity solutions. This precludes high precision post-mission orbit estimation. The main limits to real-time point solution accuracy are due to the effects of Selective Availability (SA). The objective of this research is to use the limited downlink data to provide the most accurate orbit estimation and prediction possible. We accomplish this by generating an explicit correction for SA effects based on precise ephemeris and clock solutions. This correction is solved for by adding a term for position error to the observation state relationship matrix. These error terms were used to calculate a correction to the limited telemetry data obtained from the FORTE satellite (a mission conducted by Los Alamos National Laboratories). the corrections reduced the postfit orbit error by a factor of two. The largest improvement in the position solutions was an 18m reduction in error of the alongtrack component. The velocity solutions were improved as much as 10mm/sec. An algorithm and suggestions for implementing this correction on future missions is also provided.