DOD researchers push plan aimed at avoiding worldwide GPS meltdown

By Tom Roeder | The Gazette (Colorado Springs, Colo.) | Published: February 1, 2016

COLORADO SPRINGS, Colo. (Tribune News Service) — The Defense Department's top researchers want ground-based miniature atomic clocks to avert a global catastrophe if the orbiting timepieces that make up the Colorado Springs-based Global Positioning System stop ticking.

The Defense Advanced Research Projects Agency announced a crash program to invent miniature advanced atomic clocks that reflects growing worries about the vulnerability of Air Force Space Command's GPS satellites.

"Among their myriad potential advantages, better clocks could reduce one of the more worrisome modern-day national security vulnerabilities: a deep and growing dependence on the Global Positioning System," DARPA said in a news release.

Military and civilian uses of GPS have expanded greatly since the Persian Gulf War in 1991, when the classified system was revealed to the world. The space-based timing signals broadcast by the 32 satellites operated by airmen at Schriever Air Force Base are used to control the globe's financial transactions, telephone networks and the Internet in the civilian world. For the military, GPS puts bombs on target, keeps troops from getting lost and controls the growing fleet of combat drones.

In Colorado Springs, retired Air Force Maj. Gen. Wes Clark oversaw development of the program in the 1970s. The use of GPS in everyday life makes it an attractive target for those who want to attack America, he said.

"Can you imagine our society today without GPS?" Clark asked. "It would pretty much be a global catastrophe."

Over the past year, the military has shown increasing concern about the wartime vulnerability of satellites, especially GPS. In November, Space Command boss Gen. John Hyten outlined plans to deal with attacks on satellite capabilities during an interview with The Gazette.

"I never want conflict to extend into space," Hyten said. "But we have to be able to defend ourselves."

The Army last month ran training exercises at Fort Carson that simulated how attacks on satellites would impact troops on the ground. The Joint Interagency Combined Space Operations Center at Schriever is running a series of war games to show how attacks would impact military and intelligence-gathering spacecraft.

"Within 30 seconds of a GPS shutdown, a GPS receiver would only be able to specify that it was somewhere within an area the size of Washington, D.C.," DARPA said on its website. "An hour of GPS shutdown would expand the area of uncertainty to more than the size of Montana."

A partial defense against the loss of GPS would be small, highly accurate clocks that could keep time and allow navigation computers to keep running. The clocks envisioned by DARPA, accurate to within trillionths of a second, also would fill in for GPS signals that time telephone networks, banking systems and computer transactions.

The clocks would have to be small enough to fit on military craft and be used on the battlefield. But small and atomic clock are words not normally used together.

Schriever is home to three "rubidium fountain" clocks that are accurate within a few trillionths of a second. They are used to set the time for smaller atomic clocks on the Air Force's GPS satellites.

"Those are some of the best-performing clocks in the world, but they fill a room," said Robert Lutwak, who is leading DARPA's atomic clock program. DARPA wants a clock the size of a cellphone that runs on a small battery.

Atomic clocks work by measuring the oscillations of atoms. Those oscillations can be changed by factors including gravity and temperature. That means they don't work outside a laboratory-like environment or in the controlled world of space.

"We like to think atoms are all perfect," said Lutwak, who holds a doctorate from the Massachusetts Institute of Technology and is credited with creating the world's best "chip-scale" atomic clock, a breakthrough that still lacks the accuracy needed for GPS failure.

DARPA says its $50 million clock program will have to overcome huge hurdles.

"Success will require record-breaking advances that counter accuracy-eroding processes in current atomic clocks, among them variations in atomic frequencies that result from temperature fluctuations and subtle frequency differences that can occur if the power shuts down and then starts up again," DARPA said.

©2016 The Gazette (Colorado Springs, Colo.)
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A U.S. airman uses a GPS to load coordinates at Langley Air Force Base, Va., Nov. 19, 2015.
Derek Seifert/U.S. Air Force


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