Atomic Clock Ensemble In Space Research Articles

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 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.

Test of a space cold atom clock prototype in the absence of gravity

We describe a space cold atom clock prototype and its operation on board an aircraft. We have recorded the atomic resonance in zero gravity during parabolic flights. This experiment must be considered as an essential step toward the construction of a space clock using cold atoms. In a microgravity environment, a cold atomic clock would outperform all ground-based clocks. By the year 2002, we plan to operate a cold atom clock on board the international space station. This mission is called Atomic Clock Ensemble in Space (ACES). We have also performed a preliminary accuracy evaluation of the prototype. The interrogation of the cold atoms is performed inside a TE/sub 013/ cavity. On earth, the phase variations of the field induce a relative frequency shift of about 1/spl times/10/sup -13/. Although the frequency shift is expected to strongly decrease in microgravity, this cavity does not seem suitable for a 1/spl times/10/sup -16/ frequency uncertainty.