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The current paper gives an overview on the present design baseline of the precise time facility (PTF) for Galileo. The major task of the PTF is to generate and maintain Galileo system time (GST). The current design has been worked out during Galileo phase CO by a European team of experts and provides viable solutions for most of the requirements of this key element of Galileo.

The differential calibrations of GPS common-view time-receiving equipment have been made for over twenty years. Until recently, TWSTFT calibrations have been rare due to a lack of suitable equipment. Now, the Technical University of Graz is providing such a calibration service, and this paper describes a simultaneous differential calibration of the IEN/PTB time link by GPS CV and TWSTFT. The GPS calibration, although of higher uncertainty that the TWSTFT one, provides an independent check of TWSTFT calibration technique.

The cesium fountain primary frequency standards FO2 and FOM of BNM-S RTE (Bureau National de Metrologie Systeme de Reference Temps Espace) and CSF1 of PTB (Physikalisch-Technische Bundesanstalt) have been compared using two different time transfer links: GPS P3 CV (Global Positioning System Precise Code, Common View) and TWSTFT (two-way satellite time and frequency transfer) during 10 days of almost continuous fountain operation. The resulting relative frequency differences between the remote fountains amount to several 10 -15 , whereas the total uncertainty of each clock (including statistical and systematic uncertainty) was = 10 -15 for the 10-days comparison. An experimental investigation of the noise on the two links between PTB and BNM-S RTE was performed later during two months. This allows us to deduce a link noise for a 10-day period of about 2times10 -15 .