Rubidium Atomic Frequency Standards for GPS Block IIR

Wti J. Riley

Abstract:	EG&G, Inc. has been selected to provide the Ru- bidium Atomic Frequency Standards (RAFS) for the GPS Block IIR NAVSTAR satellites. These satel- lites will replenish and upgrade the space segment of the Global Positioning System in the mid 1990s. The EG&G GPS RAFS is the latest generation of these high-performance rubidium frequency standards. They offer an aging rate in the low pplOl*/day range and a drift-corrected l-day stability in the low pplO1* range. The Block IIR version of these devices will have improved performance, higher reliability, smaller size, and greater radiation hardness. The GPS Block IIR atomic clocks have a “natural frequency” configuration whereby they output a fre- quency of about 13.4 MHz that is a submultiple of the atomic resonance. The RAFS operates at a low, fixed C-field for increased stabiity. The unit has been repackaged into a smaller 4.6” x 8.5” x 5.8” outline, but is somewhat heavier (12 lbs.) because of addi- tional radiation shielding. Elimination of the ground tuning logic and the secondary loop synthesizer (with its ovenized crystal oscillator) has reduced the RAFS complexity and improved its reliability to 0.80 for the 7.5year mission. The RAFS power consumption is only 13 W at +2O”C in vacuum. This paper describes the GPS Block IIR RAFS de- sign, including the changes and improvements made, the test results obtained, and the progress being made as this program enters the production phase.
Published in:	Proceedings of the 5th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1992) September 16 - 18, 1992 Albuquerque, NM
Pages:	537 - 545
Cite this article:	Riley, Wti J., "Rubidium Atomic Frequency Standards for GPS Block IIR," Proceedings of the 5th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1992), Albuquerque, NM, September 1992, pp. 537-545.
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