Geared toward improving spacecraft navigation, the technology demonstration operated far longer than planned and broke the stability record for atomic clocks in space. For more than two years, NASA’s Deep Space Atomic Clock has been pushing the timekeeping frontiers in space. On September 18, 2021, its mission came to a successful end. The instrument is hosted on General Atomics’ Orbital Test Bed spacecraft that was launched aboard the Department of Defense Space Test Program 2 mission June 25, 2019. Its goal: to test the feasibility of using an onboard atomic clock to improve spacecraft navigation in deep space.  The Deep Space Atomic Clock is about 10 inches (25 centimeters) on each side, roughly the size of a toaster. Its compact design was a key requirement, and an even smaller iteration will fly aboard NASA’s VERITAS spacecraft. Currently, spacecraft rely on ground-based atomic clocks. To measure a spacecraft’s trajectory as it travels beyond the Moon, navigators use these tim...