In-orbit Demonstration of a GPS Attitude Sensor

This paper details the research and development of a robust, real-time GPS attitude determination system that has now been demonstrated using the SGR-20 GPS receiver on the Topsat microsatellite. As part of this work a robust integer ambiguity resolution algorithm was developed and validated using data logged in orbit. The new algorithms were integrated into the flight determination software on the SGR-20 and this software was uploaded to the Topsat microsatellite for in-orbit testing. A number of experiments were conducted on Topsat to demonstrate real-time three axis kinematic attitude determination. These experiments included both nominal nadir pointing operations as well as large off-pointings in pitch and roll to demonstrate the capabilities of the GPS attitude sensor. The results of these experiments showed that the SGR-20 can reliably provide a kinematic attitude solution with a 1Hz update rate.