Local representations of UTC in national laboratories

TLDR

Local representations of UTC (UTC(k)) are maintained by about 69 national laboratories, vary in clock availability yet share key characteristics, and support applications such as GNSS timekeeping and frequency dissemination while anticipating future developments. The paper investigates the rationale, requirements, and practical aspects of establishing and operating a local UTC(k) time scale, including necessary equipment and algorithms. The mechanism involves national laboratories contributing clock and time‑transfer measurements to compute UTC, while implementing equipment and algorithms that generate, optimize, and compare UTC(k) time scales.

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.