Optical clock successfully tested in space

New method of measuring time could make GPS tracking hundreds of times more accurate than with atomic clocks.

18th November 2016
Optical clock successfully tested in space © Airbus Defense & Space GmbH

This view of Earth from the research rocket shows the detachment of the last booster - the moment when the optical clock began operating under microgravity © Airbus Defense & Space GmbH

You’re more likely to see someone head down in their phone than unravelling an oversized map when looking for directions these days, and there is nothing more annoying than a missed turning because your device isn’t too sure where you are. An approximate location is not helpful when going down the higgledy-piggledy back streets of a new city. This however, could all change with a new and exciting optical clock that can survive the challenges of space.

Designed by a team at the Esrange Space Centre in Sweden, the new optical clock was carried aboard a research rocket for a six-minute flight into space, and once experiencing weightlessness began to take measurements.

"Our device represents a cornerstone in the development of future space-based precision clocks and metrology," said Matthias Lezius of Menlo Systems GmbH, first author of the paper, published in Optica. "The optical clock performed the same in space as it had on the ground, showing that our system engineering worked very well."

Lost in space

Clocks measure time by counting a recurring event with a known frequency, for example a swinging pendulum. Atomic clocks measure the natural oscillation of the caesium atom, a frequency in the microwave region of the electromagnetic spectrum, however this can still have an error rate of one nanosecond over a month. On the other hand, optical clocks use atoms that oscillate about 100,000 times higher than microwave frequencies, in the visible part of the electromagnetic spectrum.

These new and improved optical clocks are set to take flight into space by the end of 2017, which could have a profound effect on the way we use GPS (global positioning systems).

The way a GPS pinpoints your location is by contacting at least four different satellites in space, measuring the time you were at a certain location using atomic clocks. Your GPS system can then estimate your location by calculating the differences among these times. Because new optical clocks ‘tick’ a lot faster than the atomic clocks, this could make the measurements 100 to 1,000 times more accurate, working out your location to a matter of centimetres.

The key development in making optical clocks so accurate are frequency combs, which slow the fast optical frequencies down to a level that are able to be referenced to a microwave-based system. Previously these have been very large and complicated, but the team at Menlo systems have managed to develop a frequency comb that is only 22x14cm and weighs 22kg, small and rugged enough to withstand the rigour of space travel and also efficient enough to come well under satellite power consumption limits.

"Applications based on frequency combs are quite important for future space-based optical clocks, precision metrology and earth observation techniques," said Lezius. "The space technology readiness of frequency combs is developing at a fast pace."

These exciting new optical clocks could also improve the way we measure greenhouse gases and gravitational waves, however only time will tell on the devices true impact.

 


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