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This paper summarizes the development of a Kalman combining algorithm, the derivation of a GPS selection technique and the results of analyzing 12 cases in demonstrating the accuracy of using GPS, totally independent of ground-based equipment, in determining the relative state of two vehicles during rendezvous The results show expected-error values ranging from 1 meter and .001 meter/sec to 24 meters and 3.1 meters/sec. The technique is sensitive to antennae offsets (unknown), GPS selection/availability and gravity gradient modeling. It is less sensitive to filter initial values than expected. Most interestingly, the relative state errors are significantly less than the individual errors in the two spacecraft absolute states and that the technique is virtually immune to refraction and relativistic effects.

There is a trend in modern space systems to contain as much of the data processing function in the spaceborne component as possible. This relieves much of the operational burden of the ground support systems, but places inordinate requirements on the spaceborne systems. Future systems will need orders of magnitude improvements in processing power, reliability/availability and function while requiring equal decreases in cost, weight and power consumption. These considerations will shape the technologies and architectures of spaceborne data processing systems for the foreseeable future.