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.
Stability Is Everything
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.”