Galileo Open Service Time performance

By the Galileo Initial Services Declaration on 15 December 2016, Galileo has officially started delivering services to users around the world. In addition to the positioning service, Galileo is able to disseminate an accurate time scale referring to UTC or providing to users interoperability with GPS and improving resilience. Galileo OS users are thus able to obtain a UTC SIS realization by applying the UTC conversion parameters to Galileo System Time (GST), broadcast in Galileo Open Service (OS) navigation message additional parameters, according to the GST-UTC conversion algorithm as described in the GALILEO ICD [1]. In order to monitor Galileo OS Time performance, the French Space Agency (CNES) which is involved in the performance monitoring from the early steps of the program has developed specific independent means using calibrated GPS/Galileo stations. In this context, three Key Performance Indicators (KPIs) are monitored: the offset between the Galileo System Time and UTC, the OS dual-frequency UTC dissemination accuracy and the Galileo to GPS Time Offset (GPGA) dissemination accuracy. This paper presents the developed monitoring means; explains the used approach for the KPIs computation and shows the results of one year of monitoring at CNES.