An official website of the United States government
Here's how you know
A .mil website belongs to an official U.S. Department of Defense organization in the United States.
A lock (lock ) or https:// means you’ve safely connected to the .mil website. Share sensitive information only on official, secure websites.

Cesium Atomic Clocks

"...till like a clock worn out with eating time."
John Dryden (1631-1701)

The long term stability of the USNO master clock is determined by an ensemble of cesium beam clocks.  The large number of these clocks that are maintained at USNO allow for the robust determination of a very stable time scale with excellent long term performance.  The average of these many cesium beam clocks are used to steer the average of the maser clocks.

The cesium beam clocks used at USNO are commercial rack-mounted devices.  These clocks feature  high-performance cesium beam tubes, with accuracy 1 part in 1012, frequency stability 8 parts in 1014, and a time domain stability of < 2 parts in 1014 with an averaging time of 5 days.

The picture above shows several environmental chambers, each of which holds up to four cesium clocks.  |  |  Navy FOIA  |  DoD Accessibility/Section 508  |  No Fear Act  |  Open Government  |  Plain Writing Act  |  Veterans Crisis Line  |  DoD Safe Helpline  |  Navy SAPR  |  NCIS Tips  |  Privacy Policy  |  Contact Webmaster
Commander, Naval Meteorology and Oceanography Command  |  1100 Balch Blvd.  |   Stennis Space Center, Mississippi 39529
Official U.S. Navy Website
Veteran's Crisis Line