Last week, China announced the successful testing of their laser experiment, which they claimed could lead to a breakthrough in fundamental physics while simultaneously improving high-precision ground-to-satellite navigation and redefining the second as a unit of time.
According to news reports, the Chinese researchers conducted the experiment in the western region of China involving two terminals in laboratories located about 70 km apart, with each terminal equipped with “a laser, a telescope, and two optical frequency combs” used for accurately measuring light frequencies. During the process, information was transmitted via laser pulses and into the two telescopes from each terminal, establishing and validating the time. The recent experiment demonstrated significant improvement over previous attempts, where laser-transmitted signals through the open air were limited to a few dozen kilometers, the lead quantum physicist Pan Jianwei from the University of Science and Technology of China (USTC) explained in a published peer-review journal on October 5. Moreover, adding that they aim “to be able to send signals over long distances to build a global network of optical clocks that would consequently play an integral role in enhancing satellite navigation services into more precise, more accurate ones.
Position, navigation, and timing (PNT) in navigation have become important features in recent years, especially in military activities with technological advances that keep growing—and the laser test is a potential sneak peek at what a future evolution of the Global Positioning System (GPS) would look like.
Ramping High-Precision Signals Using Optical Fibers
Chinese scientists previously used optical fibers, which carried high-precision signals up to a thousand kilometers. However, they could not stretch these cables between locations due to physical wire restrictions, opting to use open air instead.
Meanwhile, an outsider expert told reporters that this linking method draws many challenges, including an expensive budget and impracticalities like establishing a connection from the ground up to a spacecraft, as well as potential power interruption and atmospheric turbulence that can contribute to communication failures.
“Whenever a time signal is transmitted from one location to the other, turbulence causes the light to randomly speed up or slow down, so the time signal arrives after different amounts of flight time, ruining the timing synchronization,” said David Gozzard, an external expert fellow at the International Centre for Radio Astronomy Research in Australia.
Nevertheless, the expert lauded the Chinese team for its efforts in suppressing and minimizing turbulence effects, which could pave a clearer path toward ramping up the technology.
“By demonstrating their technology over 100km on the ground, the team have shown that it is able to handle the enormous power loss and huge amount of turbulence that will be experienced on a link from the ground to a spacecraft,” Gozzard added.
This new method also presented a fresh perspective for scientists that could redefine the second as a unit of time, which has not yet been updated since it was established in the late 1960s.
US Ongoing Efforts To Look For GPS Alternatives
While China has made significant progress on its laser-based clocks, the United States has also been doing so in recent years. In fact, earlier this year, officials from the US Defense Advanced Research Projects Agency (DARPA) asked the industry to develop optical precision timing technologies under the Robust Optical Clock Network (ROCkN) program, which will provide an alternative source of PNT information should the GPS signals fail.
The ROCkN project also aims to develop sophisticated optical timing technologies and improve the precision of small, rugged, lightweight clocks. If successful, the already advanced optical clocks would be a hundred times better while remaining portable for easier transport and use, especially on military vehicles.
“The goal is to transition optical atomic clocks from elaborate laboratory configurations to small and robust versions that can operate outside the lab,” said Tatjana Curcic, program manager in DARPA’s Defense Sciences Office. “If we’re successful, these optical clocks would provide a 100x increase in precision, or decrease in timing error, over existing microwave atomic clocks, and demonstrate improved holdover of nanosecond timing precision from a few hours to a month. This program could create many of the critical technologies, components, and demonstrations leading to a potential future networked clock architecture.”
GPS satellites are one of the most important features in today’s high-tech era, particularly for remotely controlled war machines. Most of this advanced equipment employs an atomic clock, which is responsible for accurately disseminating time across the globe and is regularly used by the US Naval Observatory (USNO) master clock in Washington. But scientists and researchers alike discovered the limitation and weaknesses of the technology, notably vulnerable to jamming and spoofing through false signals, which could make or break a mission.
No available updates on the project’s progress as of writing.
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