W.J. Riley

Abstract: EG&G, Inc. has been selected to provide the Rubidium Atomic Frequency Standards (RAFS) for the GPS Block IIR NAVSTAR satellites. These satellites will replenish and upgrade the space segment of the Global Positioning System in the mid 1990s. The EG&G GPS RAFS Rb clocks are the latest generation of the high-performance rubidium frequency standards described at this conference in 1981, 1983, 1985, and 1987. They offer an aging rate in the low pp1024 fday range and a drift-corrected 1-day stability in the low pp1014 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 cocks have u "natural frequency" configuration whereby they output a frequency of about 13.4 MHz that is a submultiple of the atomic resonance of Rb (or C). The RAFS operates at a low, fired C-field for increased stability. The unit has been repackaged into a smaller 4.6" * 8.5"r 5.8" outline, but is somewhat heavier (12 lbs.) because of additional 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 7.5-year mission. The RAFS power consumption is only 13 Wat +20°C in vacuum. This paper describes the GPS Block IIR RAFS design, including the changes and improvements made, and the test results obtained, since the last report at this conference in 1987.
Published in: Proceedings of the 22th Annual Precise Time and Time Interval Systems and Applications Meeting
December 4 - 6, 1990
Sheraton Premiere Hotel
Vienna, Virginia
Pages: 221 - 230
Cite this article: Riley, W.J., "RUBIDIUM ATOMIC FREQUENCY STANDARDS FOR GPS BLOCK IIR," Proceedings of the 22th Annual Precise Time and Time Interval Systems and Applications Meeting, Vienna, Virginia, December 1990, pp. 221-230.
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