An advanced technology for a new generation of Cold Atom Space Clock (Pharao)

Abstract

In 1994, the CNES initiated an ambitious Technology and Research Program in preparation of a new space clock development, the PHARAO project (PHARAO: Projet d'Horloge Atomique a̧ Refroidissement d'Atomes en Orbite). PHARAO has been selected by ESA to be flown on an external Express Pallet of the International Space Station during the early utilisation phase. PHARAO is one of the main components of the European payload called ACES (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 −17, 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. The paper presents the preliminary design of the PHARAO flight version which is currently based on new developments such as: • - an ultra-stable quartz oscillator at 10 MHz • - a low phase noise synthesis chain • - a laser with 100 KHz linewidth.