This is a laboratory mock-up of Deep Space Atomic Clock. It does not contain flight components, but is a rough representation of what DSAC will look like when it flies. Photo credit: NASA/JPL

Atomic Clock project Will Bring Better Navigation, More Data for Exploration Missions

By Christopher Paul

A new NASA technology demonstration mission, the Deep Space Atomic Clock, or DSAC, promises to improve data gathering and navigation for probes sent to explore the solar system.

Most current spacecraft carry Ultra Stable Oscillators, bits of quartz that vibrate at a specific frequency when current is passed through them. But these oscillators have an inherent drift, making the spacecraft’s clock too slow or fast. But scientists at JPL have been working for years to improve deep space timekeeping.

The current gold standard for timekeeping is the atomic clock, which measures the time it takes an atom to go from one energy state to another, a time which is known and constant. The GPS system flies with cesium-rubidium clocks that also have an extremely small drift, much smaller than any quartz-based clock.

But NASA’s new project, DSAC, had developed a mercury-ion atomic clock with a drift of only 1/100 of that of the GPS constellation.

But why would time-keeping be important for exploratory spacecraft? There are several reasons.

One is that it improves spacecraft navigation. If the spacecraft knows exactly what time it is, it can execute course-correction maneuvers autonomously if they are programmed ahead of time. Currently, spacecraft must be commanded to execute such maneuvers from the ground.

Exact clocks would also improve the efficiency of the Deep Space Network, NASA’s only method of keeping in touch with deep space exploration craft. Currently, the DSN must command a spacecraft to begin transmitting telemetry once it is in a position to do so. This decreases the amount of time the probe could be sending science data. If the spacecraft knew the exact time, it could therefore know that it was time to point towards Earth and begin transmitting telemetry, without being commanded by the DSN. This would also enhance DSN efficiency because while the DSN can receive multiple downlinks, it is limited in its ability to send uplinks to spacecraft. Using this method, fewer uplinks would be needed.

Read more: Atomic Clock project Will Bring Better Navigation, More Data for Exploration Missions « AmericaSpace.

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