Performance Evaluation of the GPS Yaw Bias Implementation

Yoaz Bar-Sever

Abstract:	On June 6, 1994, the US Air force implemented a yaw bias on most GPS satellites. By January 1995 the implementation was extended to all Block II satellites. The yaw bias was introduced as a way to make the yaw attitude of the GPS satellites modelable during shadow crossings. A yaw attitude model was written to simuldte the new satellite attitude during eclipse seasons. This model was made freely available to the GPS community. Proper utilization of the yaw attitude model significantly improves the overall accuracy of precise positioning with GPS. Failure to account for the new attitude model could result in large positioning errors due to the mismodeling of the antenna phase center of the GPS satellite and of the carrier phase wind-up. After 6 months experience with the biased constellation a new yaw attitude model was written that is more efficient and accurate than the first model. In this paper we discuss the implementation of the new attitude model in JPL’s IGS process which produces daily GPS orbits of the highest quality . The design of the new model will be outlined, as well as guidelines for its implementation in POD schemes. The experience gained after a year of operations with the yaw-biased GPS constellation will be analyzed to evaluate the performance of the attitude models and assess optimal estimation strategies based on the observed variability of the relevant parameters. Finally, we will discuss operational aspects of implementing the new model.
Published in:	Proceedings of the 8th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1995) September 12 - 15, 1995 Palm Springs, CA
Pages:	599 - 611
Cite this article:	Bar-Sever, Yoaz, "Performance Evaluation of the GPS Yaw Bias Implementation," Proceedings of the 8th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1995), Palm Springs, CA, September 1995, pp. 599-611.
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