PTB’s Time and Frequency Services 2018 – 2019

Dirk Piester, Andreas Bauch, Jürgen Becker, Martin Gutbrod, Tobias Klein, Thomas Polewka, Dieter Sibold, Egle Staliuniene, Kristof Teichel, Wilfried Vajen

Abstract:	By law PTB is entrusted with realization and dissemination of legal time for Germany, which is defined as UTC(PTB) plus one or two hours. During the last 24 months, including December 2019, UTC(PTB) did not deviate from Coordinated Universal Time UTC by more than 3.2 ns. The services of dissemination can be grouped in “traditional”, “IT-based”, and “based on data recording and publishing”. “Traditional”: The standard frequency and legal time transmitter DCF77 is still the most prominent part of PTB’s time services. The number of operational receivers in Germany and Europe is estimated to be more than 100 Million. Monitoring of the equipment operated at the transmitter site has been modernized over the years, and PTB is prepared to offer the service for another decade. Contractual negotiations with the operator of the transmitting facilities are going to start in 2020. The number of accesses to the telephone time service remains at a level above 1500 per day with a slight downward tendency. “IT-based”: PTB’s internet time service installations are distributed in two buildings and have been upgraded. Two devices capable to act as PTP Grandmasters have been installed, one at each location, which receive multiple timing reference inputs, and which are mutually monitored. They feed the three publicly accessible network time protocol (NTP) servers which answer about 6000 requests per second and two NTP servers for internal use. At the same time, the Grandmasters represent two Smart Meter Gateway (SMGW) administrator servers for dedicated customers. Since 2019 PTB provides a test bed for a secure NTP time service based on Network Time Security (NTS). Work is ongoing to exploit the enhanced redundancy and fully activate all monitor and control functions. In response to the perpetual popularity of services in the World Wide Web (WWW), PTB offers a service to distribute legal time via the WWW which has been coded in HTML5. It is accessible from the home page of PTB (www.ptb.de) or directly via https://uhr.ptb.de and offers the feature to display the time difference between the local system clock of the calling device and legal time as received from PTB. Via a commercial fiber-optic time transfer system Deutsche Telekom Technik (DTAG) receives signals of UTC(PTB) at sites in Bremen, Hannover, and, particularly, in Frankfurt am Main where UTC(DTAG) is realized. After a recent calibration, the time comparison between the two UTC realizations via fiber and via the GPS common-view method agree well within the calibration uncertainty. “Based on data recording and publishing”: PTB, like other national metrology institutes (NMI), has published regular reports— the so-called “Time Service Bulletins”—on the offset between GPS time derived from the satellite signals and UTC(PTB) for two decades. Since the last update, similar information on Galileo System Time (GST), including the prediction of the offset between UTC(PTB) and UTC(USNO) (via GPS) and UTC (via Galileo), based on the navigation messages of GPS and Galileo, respectively, is given. These reports shall give confidence that the broadcast GNSS signals provide a good approximation to UTC in both frequency and time. Their observance is usually required by accreditation bodies as part of the process of demonstrating traceability of corresponding measurements in accredited calibration laboratories. “Other activities”: In the framework of EURAMET project TF-1156 “GPS link calibrations in support of CCTF-K001.UTC”, PTB continues to offer calibrations of GPS signal delays in receivers of other European NMIs as well as other research institutes. In recent campaigns the institutes NMISA (South-Africa), IMBH (Bosnia-Herzegovina), and DTAG were visited. Campaigns that are ongoing at the time of writing cover NIMB (Romania), SIQ (Slovenia) and VTT (Finland), the latter employing a newly ensembled receiver kit.
Published in:	Proceedings of the 51st Annual Precise Time and Time Interval Systems and Applications Meeting January 21 - 24, 2020 Hyatt Regency Mission Bay San Diego, California
Pages:	146 - 158
Cite this article:	Piester, Dirk, Bauch, Andreas, Becker, Jürgen, Gutbrod, Martin, Klein, Tobias, Polewka, Thomas, Sibold, Dieter, Staliuniene, Egle, Teichel, Kristof, Vajen, Wilfried, "PTB’s Time and Frequency Services 2018 – 2019," Proceedings of the 51st Annual Precise Time and Time Interval Systems and Applications Meeting, San Diego, California, January 2020, pp. 146-158. https://doi.org/10.33012/2020.17295
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