Space clocks for navigation satellites

The estimation of prediction errors of the Galileo space clocks time is performed via the following steps: a) the determination of errors induced by the geodetic measurement system noise in measuring and predicting the space clock time, based on measurements of GPS clocks produced by the extended GeTT experiment, b) the elaboration of a theoretical model for estimating the clock prediction error due to the system noise, c) the determination by laboratory measurements of the prediction errors of the Galileo clocks intrinsic to the clock characteristics, d) the inclusion of the expected measurement system noise for predicting the Galileo clocks in space. Finally a preliminary study, based on the results of the extended GeTT experiment, gives a rough estimate of the space clock time error bound due to the clock and the software outliers.