FLIGHT-DATA RESULTS OF ESTIMATE FUSION FOR SPACECRAFT RENDEZVOUS NAVIGATION FROM SHUTTLE MISSION STS-69

A recently developed rendezvous navigation fusion filter that optimall y exploits existing distributed filters for rendezvous and GPS navigat ion ro achieve the relative and inertial state accuracies of both in a global solution is utilized here to process actual flight data. Space Shuttle Mission STS-69 was the first mission that gathered data from both rendezvous and Global Positioning System filters, allowing, for t he first time, a test of the fusion algorithm with real flight data. F urthermore, a precise best estimate of the trajectory is available for portions of STS-69, making possible a check on the performance of the fusion filter. In order to successfully carry out this experiment wit h flight data, two extensions to the scheme were necessary: a fusion e dit test based on differences between the filter state vectors, and an underweighting scheme to accommodate the suboptimal perfect target as sumption made by the Shuttle rendezvous filter. With these innovations , the flight data was successfully fused from playbacks of downlinked and/or recorded measurement data through ground analysis versions of t he Shuttle rendezvous filter and a GPS filter developed for another ex periment. The fusion results agree with the best estimate of trajector y at approximately the levels of uncertainty expected from the fusion filter's covariance matrix.