Spacecraft Attitude Determination using a Combination of GPS Attitude Sensor and Star Sensor Measurements

Christian Arbinger and Werner Enderle

Abstract:	The applications of GPS in space, such as orbit and attitude determination, offer several advantages, e.g. complete navigation information on board, low weight, volume and power consumption. GPS based attitude determination has many important advantages like the fast and reliable initial acquisition, the resistance against spin rates and the fact, that at least two satellites for deterministic attitude determination are always visible during the mission. GPS could also be used as a safe mode sensor. Therefore GPS based attitude determination seems very promising. But due to the achievable accuracy, implied by the baseline length and the signal noise, a GPS attitude sensor cannot be used for missions where high accurate attitude measurements are needed and the baseline lengths are restricted. For these missions, a star sensor will be the adequate attitude sensor. Star sensors are high accurate, robust and have well established algorithms. The disadvantages using star sensors are e.g. restricted field of view, operation only at low angular rates, sensor performance degradation and sometimes problems with the star identification. Taking all these individual advantages and disadvantages into account, the combination of a GPS attitude sensor and a star sensor seems extremely promising, because such a sensor combination can be applied to a broad area of missions and their requirements of a high accurate attitude. A study project has therefore been initiated at DLR/GSOC, which deals with the development of new algorithms for the combination of a GPS attitude sensor and a star sensor and the investigation of the various possibilities to support each other and therefore improve the attitude solution and the range of applicability. Preliminary results presented in this paper are obtained from an experiment on a turn table with a four antenna GPS attitude sensor and a star sensor on top of it during a ground night experiment.
Published in:	Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000) September 19 - 22, 2000 Salt Palace Convention Center Salt Lake City, UT
Pages:	2634 - 2642
Cite this article:	Arbinger, Christian, Enderle, Werner, "Spacecraft Attitude Determination using a Combination of GPS Attitude Sensor and Star Sensor Measurements," Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000), Salt Lake City, UT, September 2000, pp. 2634-2642.
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