Scientists want to put a super laser on the moon

Scientists want to build a laser in one of the coldest craters on the moon that could help lunar landers and rovers with precise navigation.

Ultrastable lasers are vital for timing and navigation systems that require extreme precision. They work by reflecting a beam between two mirrors inside a cavity. The beam bounces between the mirrors at a very precise rate, in part because the chamber stays almost exactly the same size rather than expanding or contracting. To keep this beam length stable, the mirrors are usually kept in a vacuum at extremely low temperatures, isolated from external vibrations.

The moon has hundreds of craters around the poles that never get any direct sunlight because the moon doesn’t tilt much as it spins. This makes these permanently shadowed regions exceptionally cold, with some craters predicted to be around -253 °C (20 kelvin) in the lunar winter.

Jun Ye at JILA in Boulder, Colo., and his colleagues suggested that these frigid conditions—along with the Moon’s natural lack of vibrations and virtually nonexistent atmosphere—could make these craters the perfect place for an ultrastable laser with potentially more stability at a distance than any laser on Earth.

“The whole environment is stable, that’s the key,” says Ye. “Even when you go through summers and winters on the moon, the temperature is still between 20 and 50 kelvin. That’s an incredibly stable environment.”

Ye and his team’s laser device would be similar to devices they have already built at JILA labs, called optical cavities, which consist of a chamber made of silicon with two mirrors.

The best optical cavity lasers on Earth can only remain coherent, meaning that the laser’s light waves remain synchronized for a few seconds. However, scientists believe that the moon’s laser could remain coherent for at least a minute.

This would allow it to act as a reference laser for many different lunar activities, such as maintaining a time zone on the Moon or coordinating satellites that fly in formation and use lasers to measure their distance to each other. It could even be used as a reference laser for activities on Earth, since it takes just over a second for a beam from the Moon to reach Earth, Ye says.

While it will be difficult to implement, the basic idea makes sense and could help with future moon landings, he says Simeon Barber at the Open University in Great Britain. “We have seen various recent lunar polar landers that have had suboptimal landings due to lighting conditions that prevent the use of vision-based landing systems,” says Barber. “Using a stable laser to support positioning, navigation and timing could increase the reliability of successful landings at high latitudes.”

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