Science and Technology News

Thursday, December 6, 2012

New alternate master clock arrives at Schriever

by Staff Sgt. Robert Cloys
50th Space Wing Public Affairs

12/5/2012 - SCHRIEVER AIR FORCE BASE, Colo. -- After nearly a decade of planning and development, the first of three Rubidium Fountain Clocks arrived here Dec. 4 from the United States Naval Observatory in Washington D.C.

The USNO houses the nation's most precise and stable time pieces for not only the Department of Defense, but for the entire world. Atomic measurements from clocks in the U.S. account for roughly 30% of the composite clock used to calculate Coordinated Universal Time.

"The relationship between the USNO and the 2nd Space Operations squadron is symbiotic," said Lt. Col. Thomas Ste Marie, 2 SOPS commander. "USNO maintains Universal Time using a myriad composite of atomic clocks both in Washington DC and here at Schriever AFB. In fact, each GPS satellite and monitor station is a contributor to this composite clock. The GPS constellation broadcasts that time to billions of users worldwide. It's both this technical relationship and solid organizational partnership that allows for continually record breaking time-transfer performance and navigation accuracies."

Getting the new alternate master clock from a loading dock to its final resting place in the master clock room here was no easy feat. In order to minimize damage to the equipment the clock was floated, much like a hovercraft, across a series of mats until it reached its final destination. This form of movement was used in order to minimize any potential damage to the components.

According to their website, the USNO is responsible for determining precise time and managing the dissemination of that time. Modern communications systems, such as the satellite-based Global Positioning System, increasingly depend on precise time interval.

"This clock will be a component clock in our local mean, but it will do a lot more than just that for the alternate master clock," said Jim Skinner, USNO mathematician at Schriever. "It will give us a very stable long term reference that we can use to compare to its brothers in Washington via different forms of time transfer. That should help us study seasonal and other effects in our various forms of time transfer between USNO and AMC. In the long term allowing us to learn more about how we are currently disseminating time to users."

GPS, used by millions across the globe, uses an internal timing system derived from USNO clocks that steer its timing accuracy. Specifications state that users must be able to obtain a time transfer accuracy to UTC within 40 nanoseconds. According to Ste. Marie, the accuracy at Schriever has routinely been below 4ns.

UTC is more accurate than man-made time based on the earth's rotation, according to Chris Ekstrom, division chief for clock development at the USNO in Washington D.C.
"The arrival of this clock marks a quantum leap in the accuracy of the U.S. Naval Observatory's Alternate Master Clock, which continually provides the world with precise timing via the Global Positioning System," said Col. James Ross, 50th Space Wing commander. "We are pleased to help our mission partners from USNO realize this significant upgrade."

To call and hear the official time, dial 567-6742.

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