Codeless GPS Satellite Attitude System

Gary E. Snyder Jr. and Peter F. MacDoran

Abstract:	This paper describes a codeless GPS receiver designed to determine the yaw orientation of a low Earth orbit satellite. The GPS signals are received at two directional, moderately high gain antennas at opposite ends of a structurally fixed baseline on the user satellite. The relative phase difference between the two signals received from each GPS satellite is directly dependent on the user satellite’s attitude. In order to effectively de- spread and process the GPS satellites 1575.42 MHz f&l) signals without knowledge of the codes used for the spread spectrum generation, the Ll channel of the GPS satellite’s signals are squared to produce the second harmonic of the suppressed carrier (2Ll). The 2Ll signals from the GPS satellites in view are aliased into a low f’requency band for signal processing and identification. Each GPS source is distinctly identified by the Doppler shift and Doppler rate caused by the motion of the GPS satellites relative to the user satellite. Preliminary ground based demonstration results and accuracies are presented from a one meter antenna baseline.
Published in:	Proceedings of the 6th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1993) September 22 - 24, 1993 Salt Palace Convention Center Salt Lake City, UT
Pages:	643 - 647
Cite this article:	Snyder, Gary E., Jr., MacDoran, Peter F., "Codeless GPS Satellite Attitude System," Proceedings of the 6th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1993), Salt Lake City, UT, September 1993, pp. 643-647.
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