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Cesium Atomic Clocks

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

Clock Chamber
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 one of the clock vaults containing racks of cesium beam clocks and hydrogen masers.



Commander, Naval Meteorology and Oceanography Command | 1100 Balch Blvd. | Stennis Space Center, Mississippi 39529

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