PTB’s Time and Frequency Services 2015 – 2016

Dirk Piester, Andreas Bauch, Jürgen Becker, Julia Leute, Thomas Polewka, Franziska Riedel, Dieter Sibold, Egle Staliuniene, Stefan Weyers

Abstract: The recent activities in the field of time and frequency dissemination and applications at PTB resulted in improved quality and a wider reach of the offered services. The basis of these activities remains PTB’s local realization of Coordinated Universal Time UTC(PTB). PTB’s time services comprise the operation of NTP time servers, a telephone time service and the standard frequency and time dissemination by the low frequency transmitter DCF77. The number of requests of the public NTP service approaches 7000 per second. The number of accesses to the telephone service remains steady at about 1800 per day. The standard frequency and time signal transmitter DCF77 is still the most prominent of PTB’s time services. The number of operational receivers in Germany and Europe is estimated to be more than 100 Million. In summer 2016 a calibrated GNSS receiver was installed at the transmitter site. Time comparisons between the caesium clock which serves as the reference for the transmitted signal and UTC(PTB) have since then been made with an uncertainty of 5 ns via GPS and Galileo common view. Time and frequency comparisons with institutes all over the world represent an important part of the activities. PTB continues to be the pivot in all GPS and GLONASS comparisons by which the metrology and research institutes world-wide contribute to the realization of UTC. Data from four different GNSS receivers are regularly provided to BIPM. PTB’s “golden receiver”, a legacy Ashtech ZXII-T (acronym PT02), has been found stable and reliable in the very long term, but shows annual delay variations with a peak-to-peak amplitude of about 1 ns, likely related to the outdoor temperature affecting the antenna cable delay. A possible new reference receiver was identified and is going to be tested before eventually taking over the status of PT02. PTB has accepted the role of a so-called “Group1” laboratory that should offer (in cooperation with BIPM and together with French and Spanish institutes) calibrations of GPS time links to other European NMIs and other research institutes. A so-called G1G2 campaign was finished in August 2016, during which relative receiver internal delays of in total 11 receivers belonging to the institutes DLR, METAS, VSL, and BEV were determined with reference to the PT02 delays determined by BIPM in 2014. Draft results of the 2016 BIPM campaign showed that PT02 delay changes amount to not more than 0.5 ns. A similar exercise using travelling GPS receivers was organized by SYRTE/Observatoire de Paris in the frame of the Galileo Time and Geodetic Validation Facility (TGVF) project managed by GMV, Spain, providing similar results. A TWSTFT calibration campaign was once more undertaken by the U.S. Naval Observatory and revealed the excellent long-term stability of the link between USNO and PTB via TWSTFT. The difference between successive calibration values is at the 1 ns level.
Published in: Proceedings of the 48th Annual Precise Time and Time Interval Systems and Applications Meeting
January 30 - 2, 2017
Hyatt Regency Monterey
Monterey, California
Pages: 53 - 61
Cite this article: Piester, Dirk, Bauch, Andreas, Becker, Jürgen, Leute, Julia, Polewka, Thomas, Riedel, Franziska, Sibold, Dieter, Staliuniene, Egle, Weyers, Stefan, "PTB’s Time and Frequency Services 2015 – 2016," Proceedings of the 48th Annual Precise Time and Time Interval Systems and Applications Meeting, Monterey, California, January 2017, pp. 53-61.
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