Local representations of UTC in national laboratories

Abstract

Local representations of the international time scale, Coordinated Universal Time (UTC), are maintained by approximately 69 national measurement institutes and other time laboratories. These laboratories contribute their clock and time transfer measurements for use in the computation of UTC. Although local representations of UTC, commonly called UTC(k) time scales, vary considerably, for example in the numbers of atomic clocks available, they also share many characteristics. In this paper, we examine the rationale and requirements for maintaining a local representation of UTC. Its applications might range from underpinning the reference time scale of a Global Navigation Satellite System to providing traceability for frequency and time dissemination services. We address the practical aspects of setting up and operating a UTC(k) time scale, including the equipment and algorithms that generate the time scale, optimize its performance and measure its offset from the similar time scales maintained by other laboratories. We conclude by considering briefly some future developments that may have an impact on the laboratories operating local representations of UTC.

Absolute measurement of the 1S0 − 3P0 clock transition in neutral 88Sr over the 330 km-long stabilized fibre optic link

“…The local representation of the Coordinated Universal Time (see e.g. 19 ) at AOS in Borowiec, UTC(AOS), is realized directly in the form of a 1PPS (one-pulse-per-second) by a system of an active H-maser (CH1-75A) and an offset generator (Symmetricom Auxiliary Output Generator - AOG). The active H-maser provides good stability over measurement times of up to a few days, with an Allan deviation of at an averaging time of s and decreasing as up to the averaging time of s. The AOG compensates the linear frequency drift of the maser on a daily basis and adds corrections in respect to the UTC, extrapolated from differences UTC- UTC(AOS) and UTCr-UTC(AOS) published monthly and weekly, respectively, in Circular-T 20 .…”

A DPLL Method Applied to Clock Steering

“…C LOCK steering technologies [1]- [5] play important roles in a national time and frequency laboratory or a global navigation satellite system (GNSS). The master clock of a national time and frequency laboratory must be steered to coordinated universal time (UTC).…”

Ionospheric corrections for GPS time transfer

“…The instability and uncertainty of the time transfer tends to increase as the distance between the stations increases. The uncertainty is reported to be approximately 5 ns (1 σ ) or better [ Whibberley et al ., ].…”