An advanced technology for a new generation of cold atom space clock (PHARAO)

In 1994, the CNES initiated an ambitious Technology and Research Program in of a new space clock development, the PHARAO project (PHARAO : Projet d'Ho rloge Atomique a Refroidissement d'Atomes en Orbite). PHARAO has been selected by ESA to be flown on an external Express Pallet o f the International Space Station during the early utilisation phase. PHARA O is one of the main components of the European payload called AGES (Atomic Clock Ensemble in Space). This Cesium clock, using specific laser technics for cooling the atoms, is able to reach levels of stability and accuracy in the range 10(-16) - 10(-1 7), which have never been achieved yet. But such performances do require an advanced technology, because off-the-shelf equipment would not fulfill the drastic specifications required for PHARAO.