The scientists at the US Defence Advanced Research Projects Agency (DARPA) will next month detail a new programme the group hopes will develop small, portable, battery-powered atomic clocks with stability, repeatability, and environmental sensitivity 1,000 times better than the current generation of atomic clocks.
On 1 February DARPA will detail the Atomic Clocks with Enhanced Stability (ACES) programme which will aim to develop clocks that must fit into a package about the size of a billfold and run on a quarter-watt of power. “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 stated.
One of the main applications the ACES programme wants to address is what DARPA called a large modern-day national security vulnerability: a deep and growing dependence on the Global Positioning System (GPS), not just within the military but among numerous civilian sectors of the economy.
“That’s because satellite-based atomic clocks — whose precision and accuracy reside in super-uniform, high-frequency oscillations of atomic energy states (typically those of caesium or rubidium atoms) rather than the mechanical oscillations of pendulums or the quartz crystals inside modern watches, cell phones and computers — provide the key reference signals that are pivotal to GPS. The longer that clocks on Earth or on aircraft can maintain extreme accuracy in the absence of satellite reference signals, the lower the impact of any loss of satellite contact, whether caused by natural forces or adversarial activities,” DARPA stated.
According to the agency, 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, DC. An hour of GPS shutdown would expand the area of uncertainty to more than the size of Montana. It would not take long for soldiers in deserts and sailors at sea to lose their bearings; for the critical synchrony in radiofrequency, electronic and photonic signalling to disappear; and for high-precision munitions to be stripped of the astounding navigational control that has changed the character of modern warfare, DARPA stated.
“All of our modern communications, navigation and electronic warfare systems, as well as our intelligence, surveillance and reconnaissance systems, depend on accurate time-keeping,” said program manager Robert Lutwak, who will oversee the ACES program in a statement. “It will take a collaboration of teams with skillsets from diverse fields, including atomic physics, optics, photonics, microfabrication and vacuum technology to achieve the unprecedented clock stability that we seek.”
Michael Cooney, IDG News Service
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