P. Waller, C. Plantard, European Space Research and Technology Centre – ESTEC, The Netherlands; E. Schoenemann, F. Reckeweg, S. Mejri, A. Di Mira, European Space Operation Centre – ESOC, Germany

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The ESA contribution to UTC started in 2012 based on Active Hydrogen Masers and Cs clocks operated at ESTEC, the European Space Research and Technology Centre located in Noordwijk, The Netherlands. In parallel, ESOC developed and operated a local time realization using Active Hydrogen Masers located at ESOC reference Station for ESOC operation purposes and soon as time reference for ESA Deep Space Stations. Over the last few years, an effort has been made to improve robustness, availability, and operability. These timescales have been updated and merged by providing a combined clock datafile to BIPM, including ESTEC and ESOC clocks. This combined and shared infrastructure is now fully operational and is contributing routinely to UTC. This paper will present the overall architecture of this shared infrastructure and will detail its design, operation, and performance. Both sites include a redundant timescale generation based on an ensemble of atomic clocks operated in a well-controlled environment. A different design has been selected on each site allowing for improved robustness thanks to diversity in both hardware and software. With redundant capabilities, both sites are connected via a multi-constellation / multi-frequency calibrated GNSS time and frequency transfer link. The operation is controlled by shared computing resources allowing for continuous monitoring at both sites. In addition to the contribution to UTC, this infrastructure provides a wide range of services to support multiple ESA activities. An overview of these services, their characteristics, and performances will also be reported.