Working Overtime: NASA’s Deep Space Atomic Clock Completes Mission

Jan 27, 2020
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NASA’s Deep Space Atomic Clock technology demonstration and the General Atomics Orbital Test Bed spacecraft that hosts it. Spacecraft could one day depend on such instruments to navigate deep space.



NASA's Deep Space Atomic Clock could revolutionize deep space navigation. One key requirement for the technology demonstration was a compact design. The complete hardware package is shown here and is only about 10 inches (25 centimeters) on each side.

Credit: NASA

Geared toward improving spacecraft navigation, the technology demonstration operated far longer than planned and broke the stability record for atomic clocks in space.

For more than two years, NASA’s Deep Space Atomic Clock has been pushing the timekeeping frontiers in space. On Sept. 18, 2021, its mission came to a successful end.

The instrument is hosted on General Atomics’ Orbital Test Bed spacecraft that was launched aboard the Department of Defense Space Test Program 2 mission June 25, 2019. Its goal: to test the feasibility of using an onboard atomic clock to improve spacecraft navigation in deep space.

Currently, spacecraft rely on ground-based atomic clocks. To measure a spacecraft’s trajectory as it travels beyond the Moon, navigators use these timekeepers to precisely track when those signals are sent and received. Because navigators know that radio signals travel at the speed of light (about 186,000 miles per second, or 300,000 kilometers per second), they can use these time measurements to calculate the spacecraft’s exact distance, speed, and direction of travel.

But the farther a spacecraft is from Earth, the longer it takes to send and receive signals – from several minutes to a few hours – significantly delaying these calculations. With an onboard atomic clock paired with a navigation system, the spacecraft could immediately calculate where it is and where it is going.

Built by NASA’s Jet Propulsion Laboratory in Southern California, the Deep Space Atomic Clock is an ultra-precise, mercury-ion atomic clock encased in a small boxthat measures about 10 inches (25 centimeters) on each side – roughly the size of a toaster. Designed to survive the rigors of launch and the cold, high-radiation environment of space without its timekeeping performance degrading, the Deep Space Atomic Clock was a technology demonstration intended to carry out technological firsts and fill critical knowledge gaps.

After the instrument completed its one-year primary mission in Earth orbit, NASA extended the mission to collect more data because of its exceptional timekeeping stability. But before the tech demo was powered off on Sept. 18, the mission worked overtime to extract as much data as possible in its final days.

“The Deep Space Atomic Clock mission was a resounding success, and the gem of the story here is that the technology demonstration operated well past its intended operational period,” said Todd Ely, principal investigator and project manager at JPL.

The data from the trailblazing instrument will help develop Deep Space Atomic Clock-2, a tech demo that will travel to Venus aboard NASA’s Venus Emissivity, Radio Science, InSAR, Topography & Spectroscopy (VERITAS) spacecraft when it launches by 2028. This will be the first test for an atomic clock in deep space and a monumental advancement for increased spacecraft autonomy.

While atomic clocks are the most stable timekeepers on the planet, they still have instabilities that can cause a minuscule lag, or “offset,” in the clocks’ time versus the actual time. Left uncorrected, these offsets will add up and could lead to large errors in positioning. Fractions of a second could mean the difference between safely arriving at Mars or missing the planet altogether.

Updates can be beamed from Earth to the spacecraft to correct for these offsets. Global Positioning System (GPS) satellites, for example, carry atomic clocks to help us get from point A to B. To make sure they keep the time accurately, updates need to be frequently transmitted to them from the ground. But having to send frequent updates from Earth to an atomic clock in deep space would not be practical and would defeat the purpose of equipping a spacecraft with one.
This is why an atomic clock on a spacecraft exploring deep space would need to be as stable as possible from the get-go, allowing it to be less dependent on Earth to be updated.

“The Deep Space Atomic Clock succeeded in this goal,” said JPL’s Eric Burt, an atomic clock physicist for the mission. “We have achieved a new record for long-term atomic clock stability in space – more than an order of magnitude better than GPS atomic clocks. This means that we now have the stability to allow for more autonomy in deep space missions and potentially make GPS satellites less dependent on twice-daily updates if they carried our instrument.”

In a recent study, the Deep Space Atomic Clock team reported a deviation of less than four nanoseconds after more than 20 days of operation.

Like its predecessor, the Deep Space Atomic Clock-2 will be a tech demo, meaning that VERITAS will not depend on it to fulfill its goals. But this next iteration will be smaller, use less power, and be designed to support a multi-year mission like VERITAS.

“It is a remarkable accomplishment by the team – the technology demonstration has proven to be a robust system in orbit, and we are now looking forward to seeing an improved version go to Venus,” said Trudy Kortes, director of technology demonstrations for NASA’s Science and Technology Mission Directorate (STMD) at NASA Headquarters in Washington. “This is what NASA does – we develop new technologies and enhance existing ones to advance human and robotic spaceflight. The Deep Space Atomic Clock truly has the potential to transform how we explore deep space.”

Jason Mitchell, the director of the Advanced Communications & Navigation Technology Division of NASA’s Space Communications and Navigation (SCaN) at the agency’s headquarters agreed: “The instrument’s performance was truly exceptional and a testament to the capability of the team. Going forward, not only will the Deep Space Atomic Clock enable significant, new operational capabilities for NASA's human and robotic exploration missions, it may also enable deeper exploration of the fundamental physics of relativity, much like the clocks supporting GPS have done.”

The Deep Space Atomic Clock is hosted on a spacecraft provided by General Atomics Electromagnetic Systems of Englewood, Colorado. It is sponsored by STMD’s Technology Demonstration Missions program located at NASA’s Marshall Space Flight Center in Huntsville, Alabama, and SCaN within NASA’s Human Exploration and Operations Mission Directorate. JPL manages the project.

News Media Contact
Ian J. O'Neill
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-2649
ian.j.oneill@jpl.nasa.gov
 
Mar 4, 2020
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I believe that time, is the most NON precise entity that we measure. All of our clocks use oscillation for tic rate. Atomic clocks do. Electronic clocks do. ANY clock.

A pendulum oscillation changes with height too.

This error about time......carries thru all science that follows.......and requires foolish explanations about time being a variable. Or local.

In any oscillation, we have an increase in velocity, a decrease in velocity to a full stop, and then another increase in reverse velocity, a decrease in velocity to a full stop again.

Check that out. A speed up...a speed down to stop....reverse.....speed up again....slow down again til stop......reverse......and repeat.

A force has to accelerate......then a force has to decelerate til stop.....then another direction force has to accelerate again....then decelerate.

Two forces to swing in one direction....a reversal force.....and two more forces to swing back the other way.

Think about how all those dynamics.....have to stay matched.....to give you a constant tic rate.

ANY acceleration......or a gravity gradient.....will throw that match off......and vary the tic rate.

Many, many education people believe that the change in that tic rate.......proves that TIME itself is changing.

How's that for intellect?

Let's take a vertical shaft or axle.......and attach gears at every one hundred feet......10 gears for a thousand foot vertical shaft.

Set an atomic clock beside every gear to measure the rotation rate. Spin shaft at constant rate.

What do your clocks tell you? Your clocks will tell you that each gear is moving at a different RPM.

Now, do you believe your clock?........or do you believe the physical mechanics?

Some educated people......actually believe that each gear IS rotating at a different rate!!!!!! That's how delusional our science is.

If you want to measure time.......USE a rotational time piece. A rotation only has one direction, one acceleration and both are constant. A rational clock, properly oriented, is immune to acceleration and a gravity gradient. IMMUNE TO SPACE-TIME.

Don't ever let math, or science, over ride your common sense.

This mis-conception about time, comes from the mis-conception about light.

But that's another failure of science.
 

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