Session P2a: Advanced and Future Clocks

A High-Performance Trapped ion Atomic Clock for Space and Ground Applications
E.A. Burt, R.L. Tjoelker, E. Tardiff, T. Ely, A. Matsko, J. Tien, and E. Cabrerra, Jet Propulsion Laboratory, California Institute of Technology
Location: Seaview A/B
Date/Time: Wednesday, Jan. 29, 8:35 a.m.

To address the need for better GPS autonomy and to increase the diversity of options for high-performance ground clocks, we have developed a list of necessary clock metrics that show that a space-qualified, low-SWaP clock with a new level of space clock performance [1], [2], [3] can be realized using mercury ion clock technology. Taking advantage of the successful DSAC mission [4], [5] we have developed an improved ion trap, plasma discharge light source, and more efficient electronics that have a path to a10 kg, 34 W instrument with 1e-13/sqrt(tau) and 1e-15 at a day stability as well as low drift. This level of performance could significantly enhance GPS operational autonomy with User Range Error (URE) of less than 1-meter for up to 35 days thereby enabling ground updates to be performed on a monthly time scale as opposed to multiple times per day. In addition, the new small-SWaP instrument could be easily placed in a 3U rack mount package for ground applications with hydrogen maser-like performance.
The new instrument, referred to as the High-Performance Mercury Atomic Frequency Standard (HP-MAFS), is derived from the previous Deep Space Atomic Clock (DSAC), which was successfully operated in space from 2019-2021. A significant reduction in SWaP, allowing the instrument to fit within the current clock allocation in a GPS satellite, is achieved by using lower power electronics and by integrating assemblies where possible without sacrificing performance. In the DSAC mission, instrument life was estimated to be about 5 years, limited by the plasma discharge light source. We developed a new method of light source fabrication that is expected to increase its lifetime by a factor of 2 or more.
In this talk, we will describe the technological advancements that have been made to date on this clock, the expected performance, and the current status of a breadboard version now operating at JPL.
References
[1] Lutwak, R., Emmons, D., Garvey, R.M., and Vlitas, P. “Optically pumped cesium-beam frequency standard for GPS-III,” Proc. 33rd Ann. Precise Time and Time Interval (PTTI), pp. 19-30 (2001)
[2] Riley, W.J. “Rubidium atomic frequency standards for GPS block IIR,” Proc. 22nd Ann. Precise Time and Time Interval (PTTI), pp. 221-230 (1990)
[3] Droz, F, et al. “Space Passive Hydrogen Maser - Performances and lifetime data,” Proc. 2009 IEEE International Frequency Control Symposium Joint with the 22nd European Frequency and Time forum, pp. 393-398 (2009)
[4] Tjoelker, R.L., et al., “Deep Space Atomic Clock (DSAC) for a NASA Technology Demonstration Mission,” IEEE Trans. On Ultrasonics, Ferroelectrics, and Frequency Control 63, 1034 (2016)
[5] E.A. Burt et al., “Demonstration of a trapped-ion atomic clock in space,” Nature 595, 43 (2021)