This thesis presents the experimental results obtained during the development and the ground tests of the flight model of the cold atoms space clock PHARAO. PHARAO, the first Primary Frequency Standard (PFS) for space applications, is developed by the French space agency CNES. It is a main instrument of the ESA space mission ACES: Atomic Clock Ensemble in Space with a launch scheduled on 2016. The mission is based on high performances time and frequency comparisons between a payload including PHARAO and ground based clocks to perform tests in fundamental physics. The payload will be installed on an external pallet of the International Space Station. After an introduction on atomic clocks and a summary on the ACES mission, the PHARAO architecture, optimized for microgravity environment, and its operation is described. It is followed by the measurements and the analysis of the frequency stability. On ground the frequency stability is measured at a level of 3.1 10-13 t-1/2. This value is in agreement with the different sources of noise. In space the frequency stability will reach 10-13 t-1/2. Finally the main frequency shifts are analyzed. A detailed study is given on magnetic shield properties, hysteresis and the design of the active magnetic compensation. The objective is to reduce the uncertainty of the second order Zeeman effect within few 10-17. The temperature determination of the atomic environment is also detailed and the goal is to reach an uncertainty on the blackbody frequency shift in the 10-17 range. A preliminary budget on the frequency accuracy of PHARAO on ground is evaluated at 1.1 10-15. This value is compatible with the expected accuracy budget of 3x10-16 when the clock will operate in microgravity. In the next step all the ACES instruments will be assembled for a launch scheduled on 2016.

On-ground characterization of the cold atoms space clock PHARAO

We present a highly stable and miniaturised optical system designed for a caesium satellite-borne cold atom clock (CSCAC). The optical system was integrated on a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$224\,{\mathop{\rm mm}\nolimits} \times 195\,{\mathop{\rm mm}\nolimits} \times 112\,{\mathop{\rm mm}\nolimits} $</tex-math></inline-formula> aluminium-based silicon carbide bench and emitted laser beams with four different frequencies on three fiber ports to capture, cool, prepare, and detect atoms. The optical system, utilizing a compact three-layer optical-mechanical and thermal management design, passed environmental simulation tests and adapted to a special satellite-borne environment. The optical system stability meets the laser requirements of the clock. 

/pdf/miniaturized-optical-system-for-a-caesium-satellite-borne-2800jr7y.pdf

Miniaturized Optical System for a Caesium Satellite-Borne Cold Atom Clock

We present a highly stable and miniaturised optical system designed for a caesium satellite-borne cold atom clock (CSCAC). The optical system was integrated on a $224\,{\mathop{\rm mm}\nolimits} \times 195\,{\mathop{\rm mm}\nolimits} \times 112\,{\mathop{\rm mm}\nolimits} $ aluminium-based silicon carbide bench and emitted laser beams with four different frequencies on three fiber ports to capture, cool, prepare, and detect atoms. The optical system, utilizing a compact three-layer optical-mechanical and thermal management design, passed environmental simulation tests and adapted to a special satellite-borne environment. The optical system stability meets the laser requirements of the clock.

PHARAO (Projet d'Horloge Atomique par Refroidissement d'Atomes en Orbite), which is being developed by the French space agency CNES, is the first primary frequency standard specially designed for operation in space. PHARAO is the main instrument of the ESA mission ACES (Atomic Clock Ensemble in Space) [1]. ACES payload will be installed on-board the International Space Station to perform fundamental physics experiments. Last year [2], some results on two flight model (FM) sub-systems have been presented: Microwave Source performances and Cesium Tube operating as a cold atom clock by using the other engineering model sub-systems. All the FM sub-systems have now passed the qualification process and the whole FM of the cold cesium clock, PHARAO, has been assembled and will undergo extensive tests during the first semester of 2014. The results on the cold atoms manipulation and the metrological evaluation are presented.

PHARAO flight model : Integration and "on ground" performances tests

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PHARAO flight model : Integration and "on ground" performances tests