USNO time and you

Abstract

No one can stop time, but time can stop a system. Users need to be aware of the different flavors of time, depending upon their needs. Most systems require that all their components be on a common time (synchrony), but they can't keep them on time unless they are also on a common frequency (syntony). Other systems simply require syntony. The U.S. Naval Observatory (USNO) is the timing reference for GPS. Its Master Clock (MC) is based upon 72 HP5071 cesium and 17 hydrogen maser frequency standards in three buildings and two sites, and their data are used to generate UTC(USNO). The USNO disseminates and distributes the time not only via GPS, but also with Loran, Network Time Protocol (NTP), and Two-Way-Satellite Time-Transfer (TWSTT). Our emphasis is on robustness through repeated calibration and multiplicity of systems, and we recommend this for our users as well.