The problem with most atomic clocks, the world’s most accurate known method of telling time, is they’re too large to rig on small satellites. This affects more than you’d think. Atomic clocks have uses outside of telling time—they’re also useful for a satellite’s positioning, navigation, and timing (PNT). Since they can’t be rigged up with the ultra-accurate clocks, they need to downlink with Earth to get their PNT fix.

But not anymore. Tiny, chip-scale atomic clocks (CSAC) developed by DARPA in 2004 are now being tested on board the International Space Station (ISS) after two were blasted into orbit on October 27, 2011). The CNACs are 100 times smaller than the size or regular atomic clocks (being around the size of a computer chip) and they’re 10 times more efficient.

This will be the first time the chips get used for space technologies.

According to DARPA, “The CSACs will soon be tested on board the International Space Station (ISS) in support of DARPA’s Micro-PNT program. The chips will be inserted into bowling-ball sized satellites on the ISS called Synchronized Position, Hold, Engage and Reorient Experimental Satellites (SPHERES). Once the chips have been validated as operational, the SPHERES will perform a synchronized maneuver through the ISS cabin. After the experiment, the chips containing the CSACs will be removed and tested against the atomic clock onboard the ISS.”

After sharing his hope the time-telling chips work just as well in space, Andrei Shkel, DARPA program manager, said in a press release that “A successful test after transportation, launching and space operations will mean that CSACs are one step closer to being integrated into future space platforms. Such integration should allow various space platforms more autonomy in positioning, navigation and timing.”

Briefly, the technology has a lot of potential for military use. This ties to DARPA’s Micro-Technology for Positioning, Navigation, and Timing (Micro-PNT) program.

The problem, according to DARPA, is that while war fighters rely on GPS technology, “This creates a potential challenge in instance where an intended target is equipped with high-powered jammers or if the GPS constellation is compromised.”

But this is where Micro-PNT comes in. According to DARPA, it “seeks to overcome these potential challenges by developing technologies for self-contained, chip-scale inertial navigation and precision guidance … On-chip calibration would allow for constant internal error correction to reduce drift and thereby enable more accurate devices. Trending away from ultralow drift sensors to a self-calibration approach will allow revolutionary breakthroughs in technology for positioning, navigation, and timing.”

About The Author

Joshua Philipp is the founder and editor of He's also an award-winning journalist at Epoch Times.

  • Steve Fossi

    Nice article, Joshua. DARPA sponsored the research and development of the CSAC, but the technology was commercialized and brought to market by Symmetricom, and the CSACs used in the SPHERES program are made by Symmetricom. Compared to the industry-standard 5071A (also made by Symmetricom), the CSAC offers a >400x reduction in power consumption and a >1800x reduction in volume. More information, including a full data sheet on Symmetricom’s Quantum SA.45s Chip Scale Atomic Clock, can be found at