Palm-sized atomic clock could reduce reliance on GPS

Military researchers have launched several projects in recent years to find alternatives to GPS. With so many location and navigation systems—from those in smart phones to aircraft—dependent on the Global Positioning System, the military is concerned about the threat of GPS service being lost because of natural disaster or manmade attacks.

Efforts have included an Army project to use portable sensors to track soldiers’ movements that uses gyroscopes, accelerometers and a master clock to provide navigation and an anti-ship missile that doesn’t need GPS to zero-in on its target.

The Defense Advanced Research Projects Agency is now working on another tool—a next-generation palm-size atomic clock that would be 1,000 times more accurate than current models and provide the ultra-precise timing necessary to maintain position information in the event GPS goes out.

The agency is planning a proposer’s day for the project, called Atomic Clocks with Enhanced Stability, or ACES, on Feb. 1 at the DARPA Conference Center in Arlington, Va. DARPA is planning a three-phase program for ACES, with funding budgeted at $50 million.

As DARPA points out in explaining the project, a GPS receiver’s accuracy degrades quickly one its satellite signal is lost. “Within 30 seconds of a GPS shut-down, a GPS receiver would only be able to specify that it was somewhere within an area the size of Washington, D.C.,” the agency said. “An hour of GPS shutdown would expand the area of uncertainty to more than the size of Montana.”

The atomic clocks envisioned for the ACES program clocks, which use oscillations of atoms rather than the pendulums or quartz crystals in watches, phones and computers, will maintain the extreme accuracy necessary to keep track of location for longer.

DARPA is looking for what it calls “record-breaking advances” in atomic clock design that improve accuracy by, among other things, countering the effects of variations in atomic frequencies that can happen with changes in temperature or power shut-downs and start-ups. The resulting clocks also must be about the size of a billfold, small enough to fit into a hand or a small unmanned aerial vehicle and consume no more than a quarter-watt of battery power. DARPA said it expects that the project will involves teams made up of researchers from a variety of fields, from physics to photonics.

“All of our modern communications, navigation and electronic warfare systems, as well as our intelligence, surveillance and reconnaissance systems, depend on accurate time-keeping,” program manager Robert Lutwak said. “If ACES is successful, virtually every Defense Department system will benefit.”