The next generation of telecom satellite makes the industry facing a technological rupture to reach high data throughput up to 1 terabit/s, while making communications links reconfigurable during all mission phases. That is why the introduction of optical communication technologies like laser links or photonic payloads in telecom satellites is foreseen to revolutionize the space telecom market. Hence the groundbreaking photonic payload will enable reaching the increasing demand of debit and flexibility thanks to miniaturization. In such photonic payload, the proposed optical switch will provide both the added value of optical fiber and new flexibility, redundancy and adaptability functions. Sodern, a recognized space equipment provider is presently spatializing the DirectLight® 1,55 μm Optical Switching Technology from HUBER+SUHNER Polatis Ltd (UK), the worldwide leader in optical switch technology for ground telecommunications and datacenter networks.
This paper focuses on the development activities of Sodern and Polatis on their Space Optical Switch development both for GEO 1 terabit/s high reliability and for low cost LEO constellations. An overview of the technology evaluations and design studies as well as of breadboard performance and environmental testing will be presented. Finally Sodern will explain the product development roadmap including the upcoming EQM.
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 spatial resolution of optical monitoring satellites increases continuously and it is more and more difficult to satisfy the stability constraints of the instrument. The compactness requirements induce high sensitivity to drift during storage and launching. The implementation of an active loop for the control of the performances for the telescope becomes essential, in the same way of astronomy telescopes on ground. The active loop requires disposing of informations in real time of optical distortions of the wavefront, due to mirror deformations. It is the role of the Shack-Hartmann wave front sensor studied by Sodern. It is located in the focal plane of the telescope, in edge of field of view, in order not to disturb acquisition by the main instrument. Its particular characteristic, compared to a traditional wavefront sensor is not only to work on point source as star image, but also on extended scenes, as those observed by the instrument. The exit pupil of the telescope is imaged on a micro lenses array by a relay optics. Each element of the micro lenses array generates a small image, drifted by the local wavefront slope. The processing by correlation between small images allows to measure local slope and to recover the initial wavefront deformation according to Zernike decomposition. Sodern has realized the sensor dimensioning and has studied out the comparison of various algorithms of images correlation making it possible to measure the local slopes of the wave front. Simulations, taking into account several types of detectors, enabled to compare the performances of these solutions and a choice of detector was carried out. This article describes the state of progress of the work done so far. It shows the result of the comparisons on the choice of the detector, the main features of the sensor definition and the performances obtained.