April 23, 2024

The technology demonstration was designed to improve navigation for robot explorers and operate GPS satellites. It reports on a significant milestone.

To communicate with Earth stations, spacecraft that travel beyond the Moon’s surface rely on ground stations to find out where they are and their destination. NASA’s Deep Space Atomic Clock aims to give far-flung explorers greater autonomy in navigation. The mission has published a new study that reports on their progress in improving the accuracy of space-based atomic clocks in measuring time over long periods. The paper was published in the journal Nature on June 30, 2021.

This feature is also known as stability. It also affects the operation of GPS satellites that aid people navigating on Earth. Therefore, it could increase the autonomy of the next-generation GPS spacecraft.

Engineers send signals from a distant spacecraft to Earth to calculate its trajectory. Engineers use small, refrigerator-sized atomic clocks to record the timing of these signals on the ground. This is crucial for accurately measuring the position of the spacecraft. 

These spacecraft could use atomic clocks to calculate their position and direction. However, the clocks must be highly stable. GPS satellites have atomic clocks to help us reach our destinations on Earth. However, these clocks need to be updated several times daily to ensure they are always in sync. Space-based clocks that are more stable for deep space missions would be required.

The Deep Space Atomic Clock is located in the middle bay on the General Atomics Electromagnetic Systems Orbital Test Bed spacecraft.

The Deep Space Atomic Clock, managed by NASA’s Jet Propulsion Laboratory (South California), has been operating aboard General Atomic’s Orbital Test Bed spacecraft since June 2019. According to the new study, the mission team set a new record in space-based atomic clock stability, surpassing current satellite-based clocks.

Every nanosecond counts

Every atomic clock has some level of instability. This causes an offset between the clock’s actual time and the clock’s clock. The balance can quickly increase, even though small, and spacecraft navigation could make a big difference.

The mission of the Deep Space Atomic Clock was designed to determine the clock’s stability over extended periods and observe how that changes with time. The team reported in the paper that the clock’s stability was less than four nanoseconds after 20 days of operation.

Eric Burt, co-author of this paper and atomic clock physicist at JPL, stated, “as a rule, an uncertainty in one nanosecond corresponds to an uncertainty about the distance of approximately one foot.” GPS relies on ground communication to keep its stability. Some GPS clocks need to be updated multiple times per day. This can be extended for up to a week by the Deep Space Atomic Clock, giving GPS more autonomy.

The new paper reports a five times greater stability and time delay than the team report in spring 2020. This is not a significant improvement in the clock but instead in the team’s measurement and analysis of its stability. It was possible to increase the accuracy of their measurements by using longer operating times and nearly a year’s worth of additional data.

NASA’s Deep Space Atomic Clock could revolutionize deep-space navigation. A compact design was essential for the demonstration of the technology. This complete hardware package can be seen here. It measures approximately 10 inches (25 cm) on each side.

The Deep Space Atomic Clock mission will conclude in August. Still, NASA announced that work on this technology continues: the Deep Space The new space clock, like its predecessor, is a technology demonstration. Its goal is to improve in-space capabilities by developing instruments, hardware, and software. The ultra-precise signal generated by this technology was built by JPL and funded by NASA’s Space Technology Mission Directorate. It could enable autonomous spacecraft navigation and enhance radio science observations during future missions.

A computer-aided drawing (CAD) of the linear Ion trap of the clock, which is the “heart” of the Deep Space Atomic Clock’s physics package, is slightly smaller than two rolls side-by-side. The DSAC project, a low-mass atomic clock based on mercury-ion trap technology, will be demonstrated in space. It will provide unprecedented stability for deep-space navigation.

“NASA’s selection of Deep Space Atomic Clock-2 for VERITAS speaks to the technology’s promise,” stated Todd Ely, principal investigator of Deep Space Atomic Clock and JPL project manager. “On VERITAS, we intend to put this new generation space clock through its paces and demonstrate its potential deep space navigation and science.”


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