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

Demetrios Matsakis

doi:10.1155/2008/387418

Abstract

The US Naval Observatory (USNO) has provided timing for the navy since 1830 and, in cooperation with other institutions, has also provided timing for the United States and the international community. Its Master Clock (MC) is the source of UTC(USNO), the USNO's realization of Coordinated Universal Time (UTC), which has stayed within 5 nanoseconds RMS of UTC since 1999. The data used to generate UTC(USNO) are based upon 73 cesium and 21 hydrogen maser frequency standards in three buildings at two sites. The USNO disseminates time via voice, telephone modem, LORAN, 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.

Highlights

The determination of time has been a crucial factor in navigation for centuries
With the advent of radio navigation, the need for precise time was pushed to the nanosecond level because the light travel time, when converted to distance at the approximate rate of passing 1 meter in 3 nanoseconds, was used for triangulation
In order to serve navigational needs of GPS, as well were time and frequency requirements of other users and systems, the US Naval Observatory (USNO) has specialized in real-time, robust timekeeping

Summary

INTRODUCTION

The determination of time has been a crucial factor in navigation for centuries. With the advent of radio navigation, the need for precise time was pushed to the nanosecond level because the light travel time, when converted to distance at the approximate rate of passing 1 meter in 3 nanoseconds, was used for triangulation. This determination requires knowledge or inference of the relevant clocks’ times to this level. In order to serve navigational needs of GPS, as well were time and frequency requirements of other users and systems, the USNO has specialized in real-time, robust timekeeping. This paper describes how time is generated at the USNO and transferred to the users

TIME GENERATION

TIME TRANSFER

MEASURES TO SECURE THE ROBUSTNESS OF THE MASTER CLOCK

Findings

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