AN ASSESSMENT OF TDRSS FOR PRECISION ORBIT DETERMINATION

Tracking data from the Tracking and Data Relay Satellite System (TDRSS ) are used to determine operational orbits for a variety of user space craft. These data are not routinely used for precise orbit determinati on because the Tracking and Data Relay Satellite (TDRS) orbits, derive d from Bilateration Ranging Transponder System (BRTS) tracking, are of insufficient accuracy (40-60 m). Therefore, we have investigated alte rnative orbit determination techniques to improve our knowledge of TDR S and user satellite trajectories. These techniques include incorporat ing ground based tracking of the user satellite, exploiting the enhanc ed tracking geometry provided by the user satellite, and improving the force and measurement modeling. Results from analysis of TDRSS-TOPEX/ POSEIDON (T/P) data demonstrate that the TDRSS data are powerful, that computed TDRS orbits have 3-5 m total position accuracies, and that t he corresponding T/P ephemerides have 25-40 cm accuracies.