The Pentagon’s research arm has been experimenting with a new generation of ultra-precise clocks, with the hope of one day integrating the devices into military aircraft, radars, and other systems as a reliable backup for American forces when GPS is jammed or spoofed.
To get there, the Defense Advanced Research Projects Agency, or DARPA, is tackling a vulnerability that hinges on a complex, little-known principle: GPS depends entirely on precise timing.
“Positioning, navigation, and timing is the service that we get from GPS,” said Dana Goward, president of the Resilient Navigation and Timing Foundation.
GPS satellites work by continuously broadcasting super-precise timestamps, he explained. A receiver — which can be anything from a cellphone to a military weapons system — compares signals from multiple satellites, using tiny differences in their travel times to determine its location.
Those signals, however, are so weak by the time they reach Earth that they are vulnerable to interference, Goward said. They can be intentional, like jamming, preventing a receiver from picking them up, or spoofing, feeding a receiver false information. Or it can be accidental, like a disruption caused by normal solar activity.
Disruptions, especially intentional wartime disruptions, have become a significant concern for the Pentagon — GPS is now so deeply embedded in military and civilian technology, Goward explained, that there is no equivalent alternative capable of providing the same precision.
With its new clocks, DARPA wants to make PNT more resilient for the US military, but its research could also have broad implications for other systems dependent on GPS, including banking, the internet, and electrical grids. The agency has already tested the clocks in military aircraft, ships, and vehicles, moving experimentation beyond the laboratory.
The clocks, developed through its ROCkN program, can keep GPS-quality time for more than two or three weeks without being resynchronized, DARPA program manager Mukund Vengalattore told Business Insider. Current comparable technology can maintain that accuracy for only a matter of hours, he said.
The next step in that effort, called “It’s About Time,” is focused on making those clocks practical outside research settings and determining whether they can be manufactured at scale and integrated into existing military platforms.
The ultra-advanced clocks that exist today are limited by their size, weight, power requirements, as well as cost, hindering practical use, Goward said. The current challenge is overcoming these constraints.
“A prototype is not a technology,” said Vengalattore, formerly a physics professor at Cornell University.
A 2021 government watchdog report noted concerns with military developments towards a more resilient PNT system. No single alternative PNT technology could provide everything the military needed from GPS, the report said, adding that the Pentagon would likely have to seek multiple innovative solutions.
Increased precision, like that which DARPA’s clocks could provide, could help the military synchronize information coming from large numbers of sensors, a significant new concern for troops at all levels, and more quickly assemble a coherent picture of what’s happening across battlefields.
“We know GPS can be jammed, it can be spoofed, and that has a huge impact on how our military operates in so-called electromagnetically contested areas,” Vengalattore said.
The New York Times recently reported that Russian satellites have been disrupting GPS communications for short, ten second bursts around the world since at least 2019, though it is unclear whether those efforts have been intentional. No major consequences appear to have come from those brief disruptions.
If DARPA can build its clocks to the desired specifications, the technology could eventually provide not only a reliable alternative to GPS, but also timing that is 1,000 to 100,000 times better than GPS, Vengalattore said.
One of DARPA’s current challenges is educating the military on what that level of improvement means, Vengalattore said. “Not just in terms of improved resilience to GPS spoofing or jamming,” he explained, “but entirely new capabilities that could provide a fundamental strategic advantage to the joint force.”
“We haven’t really been putting a lot of thought into, ‘what can I do better or qualitatively differently when I get access to better timing than GPS,” Vengalattore said. “If you had spent your entire life working with flashlights and I gave you a high-powered laser, it isn’t immediately apparent what you would use it for.”
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