Space Passive Hydrogen Maser - Performances and lifetime data-

Galileo navigation program is in progress under the technical supervision of the European Space Agency (ESA). The preliminary activities related to GSTBV2 experimental satellite provide the first results and the implementation of the in orbit validation (IOV) phase are in progress. Atomic clocks represent critical equipment for the satellite navigation system and clocks development has been continuously supported by ESA. The rubidium atomic frequency standard (RAFS) and the passive hydrogen maser (PHM) are at present the baseline clock technologies for the Galileo navigation payload. For the PHM, initial ground technological project related to lifetime possible limitation of the clock was initiated in parallel to satellite experimentation (GIOVE-B). Long duration frequency stability performance tests were recorded on ground demonstrating 2*10^-15 clock stability at one day (including the drift). This article gives an overview on the ground lifetime data and performance of the PHM. Extrapolation for the 12 years Galileo mission duration is discussed.