Generating a real-time time scale making full use of the available frequency standards

We propose a time-scale algorithm for the automated generation of a real-time time scale, making full use of the frequency standards available in a typical time laboratory. The time-scale algorithm is made by a pre-processing stage, a steering algorithm, and a post-processing stage. In particular, in this work we propose a set of three different steering algorithms, running in parallel and eventually producing a unique steering correction to be applied to a master clock. Each algorithm is based on a different steering reference, namely, a primary frequency standard, an ensemble clock, and the Coordinated Universal Time (UTC), or its rapid version, UTCr. Pre- and post-processing stages help to provide robustness and to cope with data gaps. The proposed algorithms have been extensively and successfully tested off-line, on real data from the time laboratory of the Italian National Institute of Metrological Research (INRiM), where an on-line test has also been performed in the period May-October 2019. Then, since the mid of January 2020, the time-scale algorithm has been applied for the generation of the Italian legal time scale, UTC(IT). We show here the results of the off-line tests and of the 5-month on-line test. The proposed strategy can be used wherever a stable, accurate, and robust time reference is needed, e.g. for a local realization of UTC in a laboratory k, UTC(k), or for generating the reference system time of a global navigation satellite system (GNSS).