A Micromechanical Gyro Package with GPS under Development for Small Pointing Satellites

The cost and complexity of large satellite space missions continue to escalate. To reduce costs, more attention is being directed toward small, lightweight satellites where future demand is expected to grow dramatically. Draper Laboratory is currently developing a three-axis stabilized control system using on-board GPS, micromechanical gyroscopes, small reaction wheels, and miniaturized microstrip phased array antennas for active line-of-sight control of a small pointing satellite. A first iteration of the rate gyroscope electronics has been designed and implemented on a single mixed-signal CMOS ASIC. The gyroscope sensor, ASIC, and supporting components are placed in a 2.5-cm X 2.5-cm flat package. Total power dissipation for the gyroscope ASIC is a small fraction of a watt. The micromechanical gyro data is optimally blended with the GPS data, thereby taking advantage of the gyro's ability to measure high-frequency dynamics and the GPS's ability to bound the error growth due to gyro drift. First-order simulation has shown that the performance of the micromechanical gyros, when integrated with GPS, is feasible for a pointing mission of 1 microradian of jitter stability and -2 milliradians (10') absolute error, for a satellite with 1 meter antenna separation.