Mercury Ion Clock for a NASA Technology Demonstration Mission.

There are many different atomic frequency standard technologies but few meet the demanding performance, reliability, size, mass, and power constraints required for space operation. JPL is developing a linear ion trap based mercury ion clock, referred to as DSAC (Deep Space Atomic Clock) under NASA's Technology Demonstration Mission (TDM) program. This clock is expected to provide a new capability with broad application to space based navigation and science. A one year flight demonstration is planned as a hosted payload following an early 2017 launch. This first generation mercury ion clock for space demonstration has a volume, mass, and power of 17 liters, 16 kilograms, and 47 Watts respectively, with further reductions planned for follow-on applications. Clock performance with an SNR*Q limited stability of 1.5E-13/τ1/2 has been observed and a fractional frequency stability of 2E-15 at 1 day measured (no drift removed). Such a space based stability enables autonomous timekeeping of Δt<0.2 ns/day with a technology capable of even higher stability, if desired. To date the demonstration clock has been successfully subjected to mechanical vibration testing at the 14 grms level, thermal-vacuum operation over a range of 42 °C, and electro-magnetic susceptibility tests.