Since June 2019, NASA's Deep Space Atomic Clock has been aboard the General Atomics Orbital Test Bed Satellite. This illustration shows the spacecraft in Earth orbit. Credit: General Atomics Electromagnetic SystemsTo communicate with Earth stations, spacecraft that travel beyond the Moon's surface rely on ground stations to find out where they are and where their destination is. NASA's Deep Space Atomic Clock aims to give far-flung explorers greater autonomy in navigation. The mission published a paper today in Nature that reported progress made in improving the accuracy of space-based atomic clocks in measuring time over long periods.This feature is also known as stability. It also affects the operation of GPS satellites that aid people to navigate on Earth. Therefore, it has the potential of increasing the autonomy of the next-generation GPS spacecraft.Engineers send signals from a distant spacecraft to Earth in order to calculate its trajectory. To accurately measure the position of a spacecraft, engineers use small, refrigerator-sized atomic clocks to record the timing of these signals. For robots on Mars and other distant destinations, the waiting time for signals can quickly add up to several minutes or even hours.These spacecraft could use atomic clocks to calculate their own position, and direction. However, the clocks must be extremely stable. To help us reach our destinations on Earth, GPS satellites have atomic clocks. However, these clocks need to be updated several times per day to ensure that they are always in sync. Space-based clocks that are more stable for deep space missions would be required.The Deep Space Atomic Clock, which is managed by NASA's Jet Propulsion Laboratory (South California), has been operating aboard General Atomic’s Orbital Test Bed spacecraft from 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 mattersEvery atomic clock has some level of instability. This causes an offset between the clock's actual time and the clock's clock. The offset can quickly increase, even though it is small, and spacecraft navigation could make a big difference.The mission of Deep Space Atomic Clock was designed to determine the clock's stability over extended periods of time, and to observe how that changes with the passage of time. The team reported in the paper that the clock's stability was less than four nanoseconds after 20 days of operation.Eric Burt, an atomic clock scientist at JPL, and co-author of this paper, stated that "as a rule, an uncertainty in one nanosecond of time corresponds to an uncertainty about 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 to up to a week by the Deep Space Atomic Clock, giving GPS potentially more autonomy.The team reported that the paper's stability and time delay are five times better than the one they reported in spring 2020. This is not a result of the clock being more stable, but the team's measurement. It was possible to increase the accuracy of their measurements by using longer operating times and nearly a year's worth of additional data.Although the Deep Space Atomic Clock mission is ending in August, NASA announced that it will continue to work on this technology: The Deep Space Atomic Clock-2 will fly on the VERITAS mission to Venus. It will be an improved version the timekeeper. The new space clock, like its predecessor, is a technology demonstration. Its goal is to improve in-space capabilities through the development of instruments, hardware and software. The ultra-precise signal that was generated by this technology, which was built by JPL and funded NASA's Space Technology Mission Directorate. It could be used to enable autonomous spacecraft navigation as well as enhance radio science observations during future missions."NASA's selection 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."Learn more NASA activates Deep Space Atomic ClockMore information: E. A. Burt et. al., Demonstration a trapped-ion atomicclock in space, Nature (2021). Information from Nature E. A. Burt and colleagues, Demonstration a trapped-ion nuclear clock in space (2021). DOI: 10.1038/s41586-021-03571-7
