Rolling GPS Receiver Development and Verification Testing for Space Application

David Yale, Awele Ndili, Jie Li, Ellen Ng, Eric Bean, Saps Buchman

Abstract:	This paper presents results of GPS receiver development and verification tests with a rolling space vehicle simulator for the Stanford Gravity Probe B (GP-B)Relativity Mission. The GP-B spacecraft will carry two redundant units of Trimble’s TANS Vector GPS receiver to provide real-time navigation solutions for orbit trim, raw GPS measurements for ground processing which will be used to generate more accurate position and velocity for science data calibration, and the Pulse-Per-Second (PPS) timing signal to payloads. During its science mission in a circular, polar orbit at the 650km height, the GP-B spacecraft will roll in an inertially fixed direction of a guide star. The roll rate will be between 0.1 rpm and 1.0 rpm. The antenna selection algorithm will determine the visibility of GPS satellites and assign a master antenna to each of six receiver channels to maintain continuity of the signal tracking. A rolling spacecraft simulator is developed for the verification tests of the GPS receiver. Four antennas are configured as they will be on the GP-B spacecraft on a horizontal axis with the GPS receiver. A variable speed DC motor mechanically coupled to the axis ‘rolls’ the GPS antennas and receiver at up to two times the anticipated roll rate of GP-B, providing real signals for software development and testing. Data of experiments with the rolling spacecraft simulator are presented in this paper, and the special points related to the roll of the spacecraft are emphasized. Some data processing techniques with a monitor named “Solution-Quality- Indicator” (SQI) are also introduced, which improves the real time performance of navigation solutions.
Published in:	Proceedings of the 12th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1999) September 14 - 17, 1999 Nashville, TN
Pages:	857 - 864
Cite this article:	Yale, David, Ndili, Awele, Li, Jie, Ng, Ellen, Bean, Eric, Buchman, Saps, "Rolling GPS Receiver Development and Verification Testing for Space Application," Proceedings of the 12th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1999), Nashville, TN, September 1999, pp. 857-864.
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