Atomic Frequency Standards Technology Roadmap for the Future GPS Satellites.

Douglas Martoccia, Ronald L. Beard, Andy Wu

Abstract:	Atomic Frequency Standards (AFS) in the GPS satellites are essential in providing GPS users accurate position, velocity and time determinations. Two Rubidium (Rb) AFSs and two Cesium (Cs) AFSs are employed for the current GPS Block II/IIA satellites. Two Rb AFSs and one Cs AFSs are planned for the GPS Block IIR satellites. However, the production of the Cs AFS is experiencing major manufacturing and testing problems, so the configuration of three Rb AFSs has been selected for at least the first ten GPS Block IIR satellites. In the GPS Block IIF program, three Cs AFSs and Rb AFS will be installed. In the United States, the capabilities of producing space-qualified AFS are presently limited to only three companies (Kernco, Frequency & Time Systems and Frequency Electronics Inc.) for the Cs AFS and one (EG&G) for the Rb AFS. The commercial market for spaceborne AFS does not exist and military usage is limited primarily to GPS. Since the market demand for the future spaceborne AFS for the GPS program will be, on the average, about twelve units per year based on three launches per year and four AFSs per satellite, this type of production rate would not provide the economic justification for the sustainment of the AFS manufactures. Also the commercial applications of the accurate AFS are seriously hampered because the accurate time can easily be obtained from the GPS receivers. Looking into the requirements for the future GPS, it is necessary to develop a long range plan for the AFS technology roadmap to assure an adequate supply now for continuous GPS sustainment. We not only have to ensure that AFS will be available in the future, we also have to address the continuing demand for the improvement in accuracy and reliability, and ease of operation, diagnostics and production by introducing new AFS technologies. In this paper we will examine the following topics: (1) Space proven AFS industrial base, (2) Special study for the AFS technology insertion plan, (3) Refinement of the current AFS technologies, (4) Development of the new AFS technologies, and (5) AFS roadmap schedule.
Published in:	Proceedings of the 10th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1997) September 16 - 19, 1997 Kansas City, MO
Pages:	1075 - 1084
Cite this article:	Martoccia, Douglas, Beard, Ronald L., Wu, Andy, "Atomic Frequency Standards Technology Roadmap for the Future GPS Satellites.," Proceedings of the 10th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1997), Kansas City, MO, September 1997, pp. 1075-1084.
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