AAS 96-182

FLIGHT TEST RESULTS FROM REAL-TIME RELATIVE GPS FLIGHT EXPERIMENT ON STS-69

J. Brazzel and Y. Park, McDonnell Douglas Aerospace; R. Carpenter, H. Hinkel, and J. Newman, NASA Johnson Space Center

Abstract

A real-time relative GPS extended Kalman filter has been developed in support of automated rendezvous with the International Space Station. The filter design exploits common satellite tracking by both chaser and target vehicle receivers and optimizes its performance during periods of asynchronous tracking. The filter is integrated with exisiting Space Shuttle crew rendezvous aiding software which runs on a 486 laptop computer under Windows. The scenario assumed in the design of this filter is that a wide variety of GPS receivers must be supported, under adverse Selective Availability conditions, and handover to a proximity operations sensor at close range precludes the need for sub-decameter solution accuracy. Therefore, the filter processes single-frequency coarse/acquisition code pseudorange measurements only. Our filtering strategy aims for maximum relative state estimation accuracy under the assumed scenario. In this work, we present real-time and post-flight results achieved with the filter on Space Shuttle mission STS-69, using GPS data from an Osborne/JPL TurboRogue receiver carried by the Wake Shield Facility free-flyer, and a Rockwell Collins 3M receiver carried aboard the Shuttle Orbiter. Our results will be used in conjunction with the results of planned follow-up experiments to mitigate the technology risk posed by the plans for automated rendezvous and docking of various Space Station international partners.