The purpose of the PHARAO project is to develop a new atomic clock generation in space. This clock takes advantage of the very low atomic velocities obtained by laser cooling techniques and the microgravity environment. <p> </p>Designing the PHARAO optical bench, which provides all the laser tools for the atomic manipulations, is a difficult task. In this paper we will give a global overview of the optical bench in term of functions, interfaces and performances. After establishing the optical parameters, which have an impact on the atomic clock performance, we present the model and software, which are used for the design and analysis of the optical system, taking into account the Gaussian laser beams. Some critical functions have been experimented and characterized to prove the model’s accuracy.
PHARAO (Projet d'Horloge Atomique par Refroidissement d'Atomes en Orbite), which has been developed by 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). ACES payload will be installed on-board the International Space Station (ISS) to perform fundamental physics experiments. All the sub-systems of the Flight Model (FM) have now passed the qualification process and the whole FM of the cold cesium clock, PHARAO, is being assembled and will undergo extensive tests. The expected performances in space are frequency accuracy less than 3.10<sup>-16</sup> (with a final goal at 10<sup>-16</sup>) and frequency stability of 10<sup>-13</sup> τ<sup>-1/2</sup>. In this paper, we focus on the laser source performances and the main results on the cold atom manipulation.
The Euclid mission objective is to understand why the expansion of the Universe is accelerating through by mapping the geometry of the dark Universe
by investigating the distance-redshift relationship and tracing the evolution of cosmic structures. The Euclid project is part of ESA's Cosmic Vision
program with its launch planned for 2020 (ref ).
The NISP (Near Infrared Spectrometer and Photometer) is one of the two Euclid instruments and is operating in the near-IR spectral region (900-
2000nm) as a photometer and spectrometer. The instrument is composed of:
- a cold (135K) optomechanical subsystem consisting of a Silicon carbide structure, an optical assembly (corrector and camera lens), a filter wheel
mechanism, a grism wheel mechanism, a calibration unit and a thermal control system
- a detection subsystem based on a mosaic of 16 HAWAII2RG cooled to 95K with their front-end readout electronic cooled to 140K, integrated on a
mechanical focal plane structure made with molybdenum and aluminum. The detection subsystem is mounted on the optomechanical subsystem
- a warm electronic subsystem (280K) composed of a data processing / detector control unit and of an instrument control unit that interfaces with the
spacecraft via a 1553 bus for command and control and via Spacewire links for science data
This presentation describes the architecture of the instrument at the end of the phase C (Detailed Design Review), the expected performance, the
technological key challenges and preliminary test results obtained for different NISP subsystem breadboards and for the NISP Structural and Thermal
We present a measurement of the 1S-2S transition frequency in atomic hydrogen by two-photon spectroscopy
yielding <i>f</i><sub>1S-2S</sub> = 2 466 061 413 187 035 (10) Hz corresponding to a fractional frequency uncertainty of 4.2×10<sup>-15</sup>.
The result presents a more than three times improvement on the previous best measurement.
The ACES (as Atomic Clock Ensemble in Space) mission, managed by the European Space Agency, has three
main objectives. The first one deals with the operation and study of the laser cooled cesium clock PHARAO
(as Projet d'Horloge Atomique à Refroidissement d'Atomes en Orbite) to reach a frequency accuracy of 10<sup>-16</sup>
in space. The second one is to perform fundamental metrology by comparing the clock signal with ground based
clocks via a two way time transfer link. The third one is to perform fundamental physics tests such as a new
measurement of the red shift at 2 parts per million and a search for variations of fundamental physical constants.
The expected time transfer resolution is 0.3 ps at 300 seconds and 7 ps per day. An H-maser developed by the
Observatoire Cantonal de Neuchatel is the second ACES clock and will be used as a stable frequency reference
for mid term duration. We give an overview of the ACES mission and its operation and present the first results
obtained with the engineering model of the laser cooled cesium clock PHARAO. This model is first developed to
validate the flight model design.
We report on the evaluation of an optical lattice clock using fermionic <sup>87</sup>Sr. The measured frequency of the
<sup>1</sup>S<sub>0</sub> → <sup>3</sup>P<sub>0</sub> clock transition is 429 228 004 229 873.7Hz with a fractional acuracy of 2.6 × 10<sup>-15</sup>. This evaluation
is performed on m<sub>F</sub> = ±9/2 spin-polarized atoms. This technique also enables to evaluate the value of the
differential Landé factor, 110.6Hz/G. by probing symmetrical σ-transitions.