NASA switches on rugged Deep Space Atomic Clock
By David Szondy
August 27, 2019
NASA has confirmed that a new atomic clock currently in low-Earth orbit has been switched on. Launched atop a SpaceX Falcon Heavy rocket on June 25, 2019 at 2:30 am EDT from the Kennedy Space Center in Florida, the Deep Space Atomic Clock (DSAC) is a miniaturized, ultra-precise mercury-ion atomic clock that is smaller, more accurate, and more rugged than any other atomic clock previously sent into space.
About the size of a toaster, the DSAC was confirmed as activated by NASA engineers on August 23 after weeks of in-orbit testing before powering up. Its purpose is to help solve the problem of how to build a spacecraft for deep space missions that can autonomously handle its own navigation problems with minimal help from Earth.
As on Earth, navigation in space is based on having clocks that are as precise and accurate as possible – and that means an atomic clock. Unfortunately, previous generations of such timepieces have either been too large, heavy and dependent on consumables to fly in space, or weren't as accurate or rugged enough to be practical for deep space missions.
Because of these limitations, missions to the Moon and beyond have relied on two-way radio communications by NASA's Deep Space Network or other deep space tracking systems. A precisely timestamped signal generated by an atomic clock is transmitted from Earth, received by the probe, and retransmitted home. The time for the round trip is measured against the timestamp and the distance to the spacecraft can be calculated.
More:
https://newatlas.com/space/nasa-switches-on-rugged-deep-space-atomic-clock/