The U.S. Naval Observatory (USNO) is charged with the responsibility for precise time determination and management of time dissemination . Modern electronic systems, such as electronic navigation or communications systems, depend increasingly on precise time and time interval (PTTI). These systems are based on the travel time of the electromagnetic signals: an accuracy of 10 nanoseconds (10 one-billionths of a second) corresponds to a position accuracy of 10 feet. In fast communications, time synchronization is equally important. All of these official systems are referenced to the USNO Master Clock.
Thus, the USNO must maintain and continually improve its clock system so that it can stay one step ahead of the demands made on its accuracy, stability, and reliability.
To find out how many cesiums and H-masers are currently in the
USNO mean timescale,
press this button:
On the basis of this computed time a clock reference system can be steered to produce clock signals which serve as the USNO Master Clock. The clock reference system is driven by a hydrogen maser atomic clock. Hydrogen masers are extremely stable clocks over short time periods (less than one week). They provide the stability, reliability and accessibility needed to maintain the accuracy of the Master Clock system.
Back to Time Service Home PageDr. Demetrios Matsakis (Matsakis.Demetrios@usno.navy.mil)