A new realization strategy for the time scale UTC(PTB)

The time scale UTC(PTB) is to be realized with an active hydrogen maser steered in frequency in a way that the maser's short-term frequency stability is preserved and that the medium-term stability is provided by the primary time references of PTB (Physikalisch-Technische Bundesanstalt). UTC(PTB) remains steered to UTC in the long term. Based on real data, we analyzed the possible ways of establishing this, searching for the best combination of data from two hydrogen masers, the primary reference clocks, CS1, CS2 and CSF1, and frequency prediction. Differences between UTC and a fictitious time scale UTCf(PTB) were calculated for various combinations, and these time differences were analyzed in terms of their time instability and their forward predictability for 45 days. It turned out that the properties of the masers during the study period were not particularly suited for the purpose. UTCf(PTB) would outperform UTC(PTB), as it has been realized up to now, only if the maser frequency was steered towards CSF1 very tightly, daily or once every two days. We discuss the properties of UTC(PTB) now and in the future, also in view of its use as a reference for steering the system time of the European satellite navigation system, Galileo, towards TAI.