Deep space exploration

NASA’s new atomic clock may revolutionize deep space exploration

The Deep Space Atomic Clock, the first device of its kind to be tested in space, is a major step towards autonomous navigation through the solar system.

The DSAC before the launch. Image: Electromagnetic Systems from General Atomics

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Launching missions beyond our planet requires humanity’s most advanced technologies and ambitious visions. But while these missions accomplish incredible feats, like landing on other planets or harboring astronauts for months in orbit, there’s one simple task they still can’t do on their own: tell the time.

Current spacecraft rely on two-way communication from Earth to keep their clocks up to date, which is a necessary process for navigation, among other functions. Now, space mission timing capabilities are set to be revolutionized by a new type of atomic clock that will “enable one-way navigation” and make “near real-time navigation of deep space probes possible”, according to a study published on Wednesday in Nature.

In 2019, NASA’s Jet Propulsion Laboratory (JPL) launched an instrument known as the Deep Space Atomic Clock (DSAC) into orbit to perform the first space demonstration of this next-generation technology, which has a dizzying range of future applications. Since launch, DSAC has lived up to expectations by achieving timing stability that is “an order of magnitude better than existing space clocks”, despite the many challenges of the space environment, the study reports.

“Over the past few years, we’ve been analyzing data, listening to it, and observing it, so it’s been constant, hard work,” said Eric Burt, atomic clock physicist at JPL and lead author of the new study. , in a call. “But now, culminating with this announcement, it’s also very, very exciting.”

Atomic clocks use the excited states of atoms to count seconds, and they are by far the most accurate timekeeping devices ever devised. Many spacecraft already embed these advanced clocks to perform complex logistics calculations, such as Global Positioning System (GPS) constellation satellites. Space missions that travel to other planets or travel deep into the solar system rely on atomic clocks on Earth to provide them with updated time measurements, a value they need to calculate their position in the planet. ‘space.

All atomic clocks currently operating in space use atomic beams or gas cells to trap timekeeping atoms in a walled-off area. These clocks are extremely accurate on short-term timescales, maintaining a level of error of no more than a billionth of a second from hour to hour, but atoms bouncing off walls “drift” this timing stability.

For this reason, GPS and other satellite clocks must be frequently updated to account for drift, making them unstable timekeepers over long periods of time. This need for long-term timing stability has been a major limiting factor for deep-space mission clocks: it is one thing to regularly correct the clocks of near-Earth GPS satellites, where communication time is low, but it would be inefficient to correct the clocks. aboard a probe traveling through the solar system, which is why these distant spacecraft rely instead on Earth clocks to keep them on track.

Deep space missions must “maintain a certain degree of accuracy for a longer period of time which allows the spacecraft to be farther away and for those spacecraft to work longer and the clock to keep ticking work,” Burt said.

DSAC is the first step towards this type of autonomous space probe capable of reading the time without having to contact the Earth. The device is a toaster-sized ‘trapped ion atomic clock’, meaning it holds atoms in place with electromagnetic forces, rather than the traditional beams and gas cells used in other atomic clocks. This design eliminates drift caused by collisions with walls and produces long-term stability, which has been demonstrated on Earth.

During its two-year journey in space, DSAC has shown that it can maintain ten times the long-term stability of existing space clocks and is not noticeably affected by space conditions such as variations in radiation, temperature or magnetic fields.

“Every time you take a test, you learn something more and raise more questions,” Burt said. “We worked hard to refine our understanding of what we already knew on the pitch.”

“Most of the clock’s sensitivities – how it reacts to temperature changes, magnetic changes, etc. – were well known and just needed to be demonstrated in the harsher space environment,” he said. he adds. “There weren’t too many surprises there, but nonetheless, the devil is in the details and we investigated quite a bit.”

As its pioneering mission draws to a close, the DSAC team has opened the door to new experiments that could revolutionize deep space travel and pave the way for a host of other near-Earth space applications. . Deep space probes that carry future versions of DSAC could autonomously pilot themselves to locations around the solar system and would not have to rely on Earth clocks to perform maneuvers such as orbital insertions or planetary landings. These clocks will also be essential for interplanetary missions that carry astronauts, as such high-stakes journeys will require real-time navigation on the spacecraft itself.

Beyond their navigational applications, trapped ion clocks could work in tandem with other instruments to illuminate a host of different questions in planetary science and fundamental physics, from mapping Europe’s subterranean seas to testing Einstein’s theory of general relativity. To that end, the next iteration of DSAC will fly on NASA’s VERITAS spacecraft, a newly approved trip to Venus, to test the clock’s capabilities on an interplanetary mission.

“The takeaway from all of this is that the technology really has tremendous reach, depending on the application,” Burt said.