The Coordinated Universal Time (UTC)

Abstract

Coordinated Universal Time (UTC) has considerably changed in recent years. The evolution of UTC follows the scientific and industrial progress by developing appropriate models, more adapted calculation algorithms, more efficient and rapid dissemination processes and a well defined traceability chain. The enormous technical progress worldwide has resulted in an impressive number of atomic clocks now available for UTC calculation. The refined time and frequency transfer techniques are approaching the accuracy requested for the new definition of the SI second. The more regular operation of primary frequency standards (PFS) increases the accuracy of UTC and opens a possible new development for time scale algorithms. From the metrological point of view all the ingredients are available for major improvements to UTC. Dissemination of UTC is done by the monthly publication of results in BIPM Circular T. This document makes a quality evaluation of local representations of UTC, named UTC(k), in national institutes, and other organizations, by giving the evolution of their offsets relative to UTC and their respective uncertainties. The clock models adopted and the time transfer techniques have progressively improved over the years, assuring the long-term stability of UTC. Each computation of UTC processes data over one month with five-day sampling and publication. A rapid solution of UTC (UTCr) has existed since 2013, and consists of the processing of daily sampled data over four consecutive weeks, computed and published weekly. It gives quick access to UTC, and allows participating laboratories to better monitor the offsets of their realizations to the reference UTC. The traditional monthly publication, containing results of all the laboratories contributing data to the BIPM for the computation of UTC was complemented after the establishment of the Mutual Recognition Arrangement of the International Committee on Weights and Measures (CIPM MRA). This time comparison, which has been the responsibility of the BIPM since 1988, added as a complement the key comparison on time defined by the Consultative Committee for Time and Frequency (CCTF) in 2006 as CCTF-K001.UTC, where the results published are those of national metrology institutes (NMIs) signatories of the CIPM MRA, or designated institutes (DIs). The traceability issues are formalized in the framework of the CIPM MRA. The development of time metrology activities in the different metrology regions, supports the actions of the BIPM time department to improve the accuracy of [UTC–UTC(k)], where the coordination with the Regional Metrology Organizations (RMOs) has a key role. This paper presents an overview of UTC.

Intercontinental comparison of optical atomic clocks through very long baseline interferometry

“…Atomic clocks based on optical transitions can reach fractional uncertainties at the 10 −18 level 1-3 surpassing by two orders of magnitude the microwave clocks 4 that realize the definition of the second in the International System of Units (SI) and are the basis of international timekeeping 5 . Given the rapid progress of optical clocks, a redefinition of the SI second as the unit of time is anticipated 6 .…”

On the possibility of getting traceable time and frequency measurements via GNSS receivers

“…Reception of GPS satellite signals started to be used for the purpose in the early 1980s (Allan and Weiss 1980). A compilation of various aspects of satellite time and frequency transfer can be found in a Handbook of the International Telecommunications Union, Radiocommunication Sector (ITU 2010), and the current status has also been sketched in the above-mentioned recent BIPM publication (Panfilo and Arias 2019).…”

“…In virtually all sectors, namely energy, telecommunications, finance, and-quite naturally-positioning and navigation, but also time and frequency metrology, the reception of signals from Global Navigation Satellite Systems (GNSS) has found widest use. The worldwide collaboration in realizing Coordinated Universal Time (UTC) as the commonly agreed time reference was recently described by Panfilo and Arias (2019) from the International Bureau of Weights and Measures (BIPM). It relies to a large extent on time comparisons involving signal reception from the US Global Positioning System (GPS).…”

Design and Development of a Cyber Security Framework for National Time Dissemination

“…Lisova [8,28] Threat and vulnerability analysis Safety and security interface is as well considered to observe which implications the developed security system has on the safety realm 4 Yadav and Yadav [30] Synchronization attack Secured SMMTS protocol is developed to find and disprove message manipulation attacks 5 Guo et al [27] time synchronization attack Effective algorithm was developed to compute the optimal attack, which takes-off the least amount of sensors and results in uncontrolled average estimation fault covariance 6 Barreto [26] Cyber-attack on packet-based time synchronization protocols It could be effectively performed irrespective of the cryptographic behavior that the PBTSP is defended with Paul et al [37] CPS test Combined the proposed CPS test into network of time-sensitive networking Suzuki et al [33], Kadowaki and Ishii [32], Kikuya et al [31] Time synchronization Studied about synchronization problems (i) To investigate the need for developing framework for national time dissemination (ii) To study about security issues faced with UTC (k) (iii) To develop and design a cyber physical secure framework for national time dissemination (iv) To examine about performance of cyber physical secure framework in cyber-secure environment.…”

“…It depends on clock readings and is increasingly reliant on the superiority of the clock comparisons. Panfilo and Arias [5] specified that the BIPM, in a corresponding strength with the world timing society, is devoted to developing and enhancing these techniques.…”