December 20, 2024 by Bob Yirka , Phys.org
Collected at: https://phys.org/news/2024-12-dual-method-precise-absolute-distance.html
A team of physicists and engineers at China’s Hefei National Laboratory has succeeded in conducting the first instance of precise absolute distance measurement over a path exceeding 100 km. The group has written a paper describing how they achieved such a feat and posted it on the arXiv preprint server.
As scientists develop ever more sophisticated technology, the need for more precise measurement grows. One such application is satellite formation flying. For it to be done as precisely as needed, new ways to very accurately measure long distances are needed—such as from a satellite to the ground, and back. In this new effort, the research team in China has found a way to measure such distances with unprecedented precision.
The work by the team involved adding an improvement to a measuring technique involving the use of an optical comb—a device that allows for averaging the time it takes for multiple wavelengths of light to travel to a target and bounce back—while also analyzing interference patterns that may have arisen during the trip.
Such technology has proven to be very precise when measuring relatively short distances. It has not worked very well over long distances, unfortunately, because the light is subject to noise and environmental factors such as humidity and temperature. In this new effort, the team overcame these problems to extend the use of optical combs to distances over 100 kilometers.
The solution, the team found, was to add a second comb at the other end of the space to be measured. Doing so caused the beams of light to interfere with one another, resulting in patterns that could be used to measure the distance between them. The technique works, the researchers note, because while the combs are indistinguishable, the interference patterns created at each end are not.
Because the beams are traveling in reverse directions relative to each other, comparison of the differences in interference patterns can be resolved, resulting in mitigating the impacts of environmental noise. The result is an extremely precise way to measure objects that are more than a kilometer apart.
The team proved the effectiveness of their approach by using it to measure objects 113 kilometers apart with a precision of 82 nm. They also note that their test is the first to achieve such precision over such a long distance.
More information: Yan-Wei Chen et al, 113 km absolute ranging with nanometer precision, arXiv (2024). DOI: 10.48550/arxiv.2412.05542
Journal information: arXiv
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