The ongoing development of micromechanical inertial systems which require very little power suggests the concomitant development of a low power GPS receiver. The combination of such an interferometric receiver with inertial instruments would fill the need forrna low cost, light weight, low power attitude determination system for use in small low cost satellites with modest accuracy requirements (0.1 to 0.5 deg.). 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. This study looks at the implications of this strategy on the details of the receiver operation and design including re-acquisition, and the trade between pre- and post-detection integration as well as power consumption. The accuracy of such a system as a function of the interval between GPS measurements was assessed. Depending on this interval and on other parameters such as IMU quality, antenna baseline, etc., 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. Volume, weight and power 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.
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