GPS Block II Operations Reach A Ten Year Benchmark: Managing A Mature Constellation

Gary L. Dieter, Jack Taylor

Abstract:	February 14, 1999 marked the ten year anniversary of the successful launch of SVN 14 (PRN 14). This date serves as a significant benchmark, as SVN 14 is the first Block II satellite to provide a decade of GPS on-orbit operations. Since 1989, a team of 2d Space Operations Squadron, Boeing, and other contractors have striven to provide users worldwide with the best GPS navigation and timing performance possible. As years of Block II experience have accumulated, the lessons learned at Schriever AFB have allowed the GPS operations support team to streamline operations processes and greatly improve satellite vehicle efficiency. It is this experience which is to be drawn on in the future to continue the trend of GPS operations excellence, both in the realms of Block II/IIA and IIF. Reflecting upon the accomplishment of a decade of service, this paper describes a view of the GPS Block II/IIA program from a historical perspective. First, current constellation status is presented to provide insight into how space and ground system expectations have been met. The paper then discusses specific examples describing operations which have been developed or improved to achieve a global system of navigation and timing signals which has stressed the very limits of early 1980’s design and technology. Areas of interest include maintenance operations which have been streamlined to minimize satellite mission outage times, performance monitors which have aided in predicting satellite degradation, and operations which have been developed to keep degraded spacecraft fully functional. Specific examples include geographic node modeling, atomic frequency standard maintenance operations, L-band monitoring, Kalman filter state initialization and tuning, reaction wheel rundown tests, solar array capacity tests, and operations with three reaction wheels. Potential operation with two reaction wheels is also discussed as an area of future improvement. To the GPS user, the navigation and timing signals are the bottom line. This paper demonstrates how the quality,reliability, and longevity of those signals have been optimized by a military/contractor team that is constantly improving GPS system operations. Exposure to these issues, often invisible to the user community, provides the GPS user additional insight into how the operations community has provided a decade of Block II navigation and timing service.
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:	2261 - 2268
Cite this article:	Dieter, Gary L., Taylor, Jack, "GPS Block II Operations Reach A Ten Year Benchmark: Managing A Mature Constellation," Proceedings of the 12th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1999), Nashville, TN, September 1999, pp. 2261-2268.
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