The PHARAO time and frequency performance verification system

The PHARAO cold atoms clock, which is scheduled to fly in 2007 with the ESA ACES mission, will be assembled and tested at the CNES facilities in Toulouse. Assembly of the engineering model has already started with electrical integration of the on-board computer and the microwave source. Verification of the metrological performances of both the engineering and flying models is one of the main challenges of integration activities. A test at the 10/sup -15/ level is needed to extrapolate the behaviour of the clock performances in space in the 10/sup -16/ range. The paper describes the detailed architecture and metrological features of this time and frequency test system with a preliminary evaluation of the metrological performances of the PHARAO microwave source.