Time and Frequency Activities at the U.S. Naval Observatory

Demetrios Matsakis

Abstract:	The U.S. Naval Observatory (USNO) has provided timing for the Navy since 1830 and via DoD Directives 4650.05 and 4650.07 is the sole source of timing for the Department of Defense. In cooperation with other institutions, the USNO also provides timing for the United States and the international community. Its Master Clock (MC) is the source of UTC(USNO), USNO’s realization of Coordinated Universal Time (UTC), which has stayed within 5 ns rms of UTC since 1999 and within 4 ns rms in 2011. The data used to generate UTC(USNO) are based upon 87 cesium, 38 hydrogen maser, and now also 4 rubidium fountain frequency standards in four buildings at two sites. USNO disseminates time via voice, telephone modem, Network Time Protocol (NTP), GPS, and Two-Way Satellite Time Transfer (TWSTT). This paper describes some of the changes being made to meet the future needs for precision, accuracy, and robustness. Further details and explanations of our services can be found online.
Published in:	Proceedings of the 43rd Annual Precise Time and Time Interval Systems and Applications Meeting November 14 - 17, 2011 Hyatt Regency Long Beach Long Beach, California
Pages:	107 - 124
Cite this article:	Matsakis, Demetrios, "Time and Frequency Activities at the U.S. Naval Observatory," Proceedings of the 43rd Annual Precise Time and Time Interval Systems and Applications Meeting, Long Beach, California, November 2011, pp. 107-124.
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