A Low Cost Low Power INS/IGPS Spacecraft Attitude Determination System

Richard Phillips, Walter Guinon, Roy Setterlund, Antonio Giustino

Abstract:	The anticipated proliferation of small low cost communication and science satellites with modest (~ 0.1 -0.5 deg) pointing requirements and correspondingly limited power, mass, and cost budgets calls for a very low volume, mass, power, and cost attitude determination system. Micromechanical inertial sensors and an interferometeric GPS (IGPS) attitude determination receiver potentially offer such a system Power consumption by the GPS receiver can be reduced by turning off the RF front end, the frequency synthesizer, the reference oscillator and the digitizer for brief intervals of time while using the inertial system to maintain adequate attitude knowledge and to simplify obtaining subsequent IGPS attitude updates without time consuming integer ambiguity resolution. The study predicts the accuracy of such a system as a function of inertial instrument quality, antenna array geometry, and the interval between IGPS measurements. Depending on the exact values chosen, system power consumption on the order of one watt or less can be achieved. Accuracies in the 0.1 to 0.5 degree regime are readily achievable. Results are presented using actual IGPS measurements blended with actual micromechanical gyro data. Modeling assumptions and filter tuning are discussed as well as the importance of "model based" estimation techniques to further improve system performance. Volume and weight projections are based on existing technology and hardware, leading to a system concept for a spacecraft attitude determination that could be of enormous benefit for small satellites.
Published in:	Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998) September 15 - 18, 1998 Nashville, TN
Pages:	1819 - 1829
Cite this article:	Phillips, Richard, Guinon, Walter, Setterlund, Roy, Giustino, Antonio, "A Low Cost Low Power INS/IGPS Spacecraft Attitude Determination System," Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998), Nashville, TN, September 1998, pp. 1819-1829.
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