NPL working with ESA to SWAP all the clocks

PNT technology, such as GPS and Europe’s Galileo, currently relies on atomic clocks that use microwave radiation to lock on to particular stable atomic microwave absorption reference frequencies. But in the past decade, optical atomic clocks - where lasers interrogate and lock on to optical atomic absorptions at much higher frequencies – have emerged as a more robust alternative to microwave-based technology.

In light of this, NPL is developing robust, portable optical clocks with low size, weight and power (SWAP) which are more accurate and reliable than microwave systems. A key feature of the new clocks will be NPL’s cubic optical cavity technology, which acts as a compact opto-electronic clock control unit and maintains the frequency stabilisation of the clock’s lasers.

“The NPL cubic cavity is a critical part of our aims to deliver atomic timekeeping that underpins the technologies that are part of our everyday lives,” Cyrus Larijani, strategic business development manager for Space and Nuclear at NPL, said in a statement.

“The uptake of the next-gen technology will enhance the UK’s leading position in space-based PNT systems.”

NPL will build on its current cubic cavity technology to create a low-SWAP Clock Control Unit (LS-CCU) specifically for use in next-generation PNT systems. The device will be designed to withstand the rigours of spaceflight and will undergo preliminary laboratory-based testing under simulated space conditions.

Stefano Binda, NAVISP Element 1 manager, ESA, said: "Robustness of PNT systems and other important applications will benefit significantly from the exceptional expected performance of space optical clocks, and I am very pleased that ESA works together with NPL, one of the most authoritative organisations in time-keeping systems in the world, towards the development of a Clock Control Unit, the necessary building block of a fully functional optical clock."

According to NPL, there are a range of potential applications beyond PNT for cubic cavity-stabilised lasers in space under consideration by various space agencies.

In the NASA/ESA Next Generation Gravity Mission (NGGM) due for launch in the late 2020s, the technology could be used to measure the Earth’s gravity field as a function of position on the Earth’s surface.

The lasers could also be used as references for space-based gravitational wave measurements in the future NASA/ESA Laser Interferometer Space Antenna (LISA) mission, projected for the 2030s.