Ultrastable Lasers in Moon's Permanently Shadowed Craters Could Enable Lunar GPS System
Summary: Researchers at the National Institute of Standards and Technology (NIST) have proposed placing ultrastable lasers inside the moon's permanently shadowed craters near the south pole, leveraging the extreme cold and vacuum conditions to build a GPS-like navigation network for future Artemis astronauts and lunar spacecraft.
Background
As NASA prepares for long-term Artemis missions and future lunar bases, Lunar GPS concepts have gained increasing attention. Scientists and space agencies have spent years developing positioning, navigation and timing (PNT) systems for the moon, including orbiting navigation satellites, radio beacons and atomic clocks similar to those powering Earth's GPS network.
NIST researchers have now added a novel twist: housing ultrastable lasers inside the moon's permanently shadowed craters.
Why Permanently Shadowed Craters?
Permanently shadowed craters never receive direct sunlight due to the moon's low axial tilt. Hidden in perpetual darkness, these craters remain colder than Pluto — dipping to around minus 223 degrees Celsius (minus 370 degrees Fahrenheit). Scientists have long targeted them as potential reservoirs of frozen water to support future lunar settlements.
Now researchers believe those same harsh conditions could make them ideal natural laboratories for precision laser systems.
How It Would Work
A highly stable laser produces light with an almost perfectly constant frequency, allowing multiple lasers to precisely measure distances between objects. On Earth, such systems require complex cryogenic cooling and vibration isolation because even tiny temperature shifts can destabilize the laser.
Inside a permanently shadowed lunar crater, nature does much of this work for free. The extreme cold, combined with the moon's naturally high-vacuum environment and relatively low vibration levels compared to Earth, could allow silicon optical cavities to operate with almost no thermal expansion — providing the stability needed for navigation systems that rely on precise laser frequencies.
The study, published May 8 in the Proceedings of the National Academy of Sciences (PNAS), proposes using a silicon optical cavity — a device that stabilizes laser light by reflecting it between mirrors separated by an incredibly precise distance.
Lead author Jun Ye stated: "As soon as I understood what the permanently shadowed regions can offer, I felt that this would be the most ideal environment for a super-stable laser."
Applications
Once deployed, the optical cavity would stabilize a nearby laser by locking its light to a single, highly precise frequency. The resulting signal could function as a GPS beacon for lunar spacecraft, while linking with satellite-based atomic clocks to form the backbone of "the first optical atomic clock on an extraterrestrial surface."
This could allow future Artemis astronauts and rovers to navigate the rugged lunar south pole without heavily relying on Earth-based tracking systems.