A toaster-sized atomic clock orbiting Earth is 25 times more accurate than existing space clocks and will soon be tested on a mission to Venus. The highly accurate timepiece could improve navigation for deep-space missions.
Atomic clocks work by measuring the radiation emitted by electrons as they hop from lower to higher orbits around atoms. These clocks are used in space now, but the atoms can collide with the walls of the vessel containing them, affecting accuracy. The Deep Space Atomic Clock (DSAC) solves this problem by using mercury ions as the timekeeper, which carry a charge and so can be kept away from the clock鈥檚 wall by an electromagnetic field.
NASA launched the DSAC in 2019 to test its stability and long-term reliability in orbit and has now published research that shows its accuracy far exceeds any other clock in space. at NASA鈥檚 Jet Propulsion Laboratory in California and his colleagues found that the DSAC drifted by only 4 nanoseconds overall after 23 days. Current atomic clocks in space, such as those used on GPS satellites, would see a drift of around 100 nanoseconds over the same period.
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Reducing the error rate is essential for accurate navigation, says Burt. Many space missions currently navigate using room-sized atomic clocks on Earth. These are highly accurate but energy-intensive, and their signals take longer to arrive the further a spacecraft gets from Earth.
Meanwhile, current atomic clocks miniaturised for use in space are significantly less accurate than is needed to maintain accurate autonomous navigation. A more accurate clock aboard a spacecraft would allow it to calculate its own trajectory instead of waiting for signals from Earth.
A DSAC will be included on NASA鈥檚 recently announced VERITAS mission to Venus. That craft will include its own timekeeper, based on a standard quartz clock, but will carry a DSAC as a testbed for future missions. The team is also working on a version of the atomic clock that would fit inside the space occupied by the less accurate clocks currently fitted to GPS satellites.
Nature
