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View of the Mainflingen long-wave radio station for transmission of the DCF77 signal: transmitter building (in the back), antenna building (yellow bricks) and antenna masts.

Dissemination of Time

Working Group 4.42

Profile

News

Towards the end of 2016 an important milestone was reached by the European satellite navigation system Galileo. In the Notice Advisory to Galileo Users (NAGU) 2016063 of 15.12.2016 the Galileo Initial Open Service was declared operational.

Editor of NAGUs is the European GNSS Service Centre, URL:
https://www.gsc-europa.eu/galileo-gsc-overview/the-european-gnss-service-centre.Here one can find information on the constellation and details on orbit parameters of the Galileo satellites.

PTB makes use of Galileo signals for time comparisons between its facilities in Mainflingen (DCF77) and Braunschweig, and in the context of the Galileo Time and Geodetic Validation Facility, under contract of the European Space Agency ESA.

The figure shows measurement results between the local reference time UTC(PTB) and Galileo Systemzeit GST, derived from observation of 11 satellites on 25.12.2016.

The legend states Exx, the signal identification XX of the Galileo satellites and _SSNN the satellite family SS and number NN of the satellite within the family. Further 7 satellites were in orbit towards end of the year, but could not or not yet be used for time transfer.

 

 

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Research/Development

In cooperation with various institutes our working group is striving for an improvement of the performance of satellite-based time comparisons.

Starting 2010 the time scale UTC(PTB) has been realized using an active hydrogen maser as physical source, steered with respect to the very accurate and long-term stable caesium fountains. In the meantime, other institutes have followed our example as one can see here.

Not far from now, a communication terminal reaching to the International Space Station will be put in operation in PTB. This will allow time comparisons between PTB and the Atomic Clock Ensemble (ACES) in Space with unprecendented accuracy. In early 2016 one can see structures of the ground terminal  on a roof of a high building of PTB, waiting for completion with the electronics inside. 

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Services

The dissemination of legal time is prerequisite for the availability of accurate time in our country (and beyond).

Radio-controlled clocks are very popular in Germany and in common usage. Signals of the long-wave transmitter are received by estimated 100 million receivers in Germany and almost all over Europe.

Of similar significance ist he time dissemination vie the Internet that is pursued by our colleagues from PTB’s IT-sector (Q.42). Our group provides the timing information that is then distributed using the Network Time Protocoll (NTP).

A few staff members of our group are active as technical consultants for the Deutsche Akkreditierungsstelle DAkkS. In total 60 accreditated calibration laboratories with time and frequency activities are supervised thereby in Germany.

 

 

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Information

WG 4.42 provides a large set of measurement data that can be used for obtaining traceability of local measurements to the national standard and to legal time. Access is via ftp.ptb.de/pub/time.

The folder "bulletins" contains the weekly Time Service Bulletin (filename  ptb_WWJJ.tsb, WW: week number of the year, JJ year number, 16 for 2016). It contains the difference between GPS time and time disseminated via DCF77 with respect to UTC(PTB) and to UTC.

Another type of bulletin is ptb_mmjjjj.dcf and log_jjjj.dcf which inform about the properties and service interruptions of the DCF77 transmitter

The folder "GNSS" contains up-to-date GNSS observation data. The sub-folders contain data in format CGGTTS and RINEX. A Readme-file in the main folder explains the use of the data.

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News

Towards the end of 2016 an important milestone was reached by the European satellite navigation system Galileo. In the Notice Advisory to Galileo Users (NAGU) 2016063 of 15.12.2016 the Galileo Initial Open Service was declared operational.

Editor of NAGUs is the European GNSS Service Centre, URL:
https://www.gsc-europa.eu/galileo-gsc-overview/the-european-gnss-service-centre.

Here one can find information on the constellation and details on orbit parameters of the Galileo satellites.

PTB makes use of Galileo signals for time comparisons between its facilities in Mainflingen (DCF77) and Braunschweig, and in the context of the Galileo Time and Geodetic Validation Facility, under contract of the European Space Agency ESA.

The figure shows measurement results between the local reference time UTC(PTB) and Galileo Systemzeit GST, derived from observation of 11 satellites on 25.12.2016.

The legend states Exx, the signal identification XX of the Galileo satellites and _SSNN the satellite family SS and number NN of the satellite within the family. Further 7 satellites were in orbit towards end of the year, but could not or not yet be used for time transfer.