Space Shuttle Precision Orbit Determination in Support of SLA-1 Using TDRSS and GPS Tracking Data

Abstract

On January 11, 1996, the Space Shuttle Endeavor, mission STS-72, was launched, carrying aboard the first of four Shuttle Laser Altimeter (SLA) experiments. In support of SLA-1, precise orbits have been computed from Tracking and Data Relay Satellite System (TDRSS) Doppler observations. In some cases, these data were combined with Global Positioning System (GPS) pseudorange observations. Traditionally, the Tracking and Data Relay Satellite (TDRS) orbits themselves have been the dominant source of error in Shuttle orbit determination during quiescent attitude periods. However, a new technique utilizing TOPEX/Poseidon’s (T/P) precise orbit knowledge plus the TDRSS-T/P Doppler tracking is used to significantly reduce the TDRS orbit errors. That approach, along with improved modeling and parameterization have allowed us to compute precise Shuttle orbits from TDRSS-Shuttle Doppler tracking data. Orbit overlap comparisons indicate these Doppler-derived orbits have a meter level (1σ) radial precision, and they agree radially with the combined Doppler and GPS derived orbits at the 1.5 m level (1σ).