PTB's Time and Frequency Activities in 2008 and 2009

The Physikalisch-Technische Bundesanstalt PTB maintains the German national time scale, disseminates time and frequency for both business and general public, and undertakes research to improve its facilities. This report covers the activities of PTBs Time Dissemination Working Group during 2008 and 2009. PTBs time scale UTC PTB is based on the primary clock CS2 and an associated phase micro-stepper to keep the time scale in reasonable agreement with UTC. CS2 and the other primary standards, CS1, CSF1, and CSF2, are part of PTBs ensemble of atomic clocks whose data are provided for the computation of TAI. During 2009, the commercial clocks have been moved step by step to a new clock room with improved operational conditions and state-of-the-art cabling. A broad range of satellite time-transfer equipment is being operated to enable time scale comparisons with other institutes all over the world. Singlemulti-channel GPS receivers as well as so-called geodetic receivers enable frequency and time transfer with the state-of-the-art evaluation techniques CA code, P3, carrier phase, PPP. Two-way satellite time and frequency transfer TWSTFT is made routinely with several stations in Europe, the US, and Asia. Several calibration campaigns have been performed, partly with substantial support of USNO and BIPM, which allowed verification of the time-transfer uncertainty using PTBs current equipment. PTB provides services to disseminate time and frequency within Germany. The most prominent example is the low-frequency transmitter DCF77, which is widely used. In 2009, PTB looks back on 50 years operation of this service. Other time services are the NTP-servers as well as the telephone time service to synchronize computer via Internet or modem connection, respectively. The capability of the NTP infrastructure was enhanced by the introduction of an additional NTP server.