Rubidium Standard Marks 20 Years in GPS Orbit

A rubidium frequency standard has stood the test of time, with 20 years of failure-free operation aboard a U.S. Air Force GPS satellite.

Both military troops and private citizens rely on the navigation precision of the Global Positioning System (GPS), and that in turn depends on the time-keeping accuracy and frequency stability of the system’s satellites and its frequency reference oscillators. In support of the GPS system, the supplier of its rubidium (Ru) atomic frequency standard (RAFS), Excelitas Technologies, recently celebrated 20 years of continuous, reliable, failure-free on-orbit operation of the RAFS aboard one of the U.S. Air Force’s GPS satellites. The rubidium frequency reference was placed in orbit as part of the U.S. Air Force’s first GPS IIR satellite on July 23, 1997 and remotely activated on August 13 of the same year.

The RAFS technology is a critical time- and frequency-keeping component of the navigation payloads designed by Harris Corp. for GPS IIR, GPS IIR-M, and next-generation GPS III satellite systems produced by Lockheed Martin. A total of 12 GPS IIR and 7 GPS IIR-M satellites are currently in orbit with the RAFS technology from Excelitas, laying claim to more than 250 total years of reliable operation. The 19 satellites represent more than 60% of the current GPS satellite constellation. The first GPS III satellite with an Excelitas RAF aboard is expected to launch in 2018.

“Achieving this 20-year IIR satellite milestone, and the GPS constellation’s continued good health, emphasize Excelitas’ continued long-term leadership in space-qualified and military tactical time frequency standards,” said Doug Benner, executive vice president of Excelitas’ Defense and Aerospace Group. “We are proud of our contribution to these global positioning, navigation and timing systems and we look forward to continuing this legacy for many years to come.”

“Excelitas’ high reliability RAFS technology was developed specifically for mission critical space applications,” added John Vaccaro, technical director of RAFS Systems for Excelitas Technologies. “We have built over 125 atomic standards with world-class stability and low drift combined with the small size, low weight, and power advantages. The Excelitas RAFS is recognized as an enabling technology for global positioning systems.”

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