English: The Deep Space Atomic Clock (DSAC) is a miniaturized, ultra-precise mercury-ion atomic clock for precise radio navigation in deep-space. It is orders of magnitude more stable than existing navigation clocks, and has been refined to limit drift of no more than 1 nanosecond in 10 days. It is expected that a DSAC would incur no more than 1 microsecond of error in 10 years of operations. It is expected to improve the precision of deep-space navigation, and enable more efficient use of tracking networks. The project is managed by NASA's Jet Propulsion Laboratory and planned for test deployment in low Earth orbit sometime in 2016.