Enabling planetary science across light-years. Ariel Definition Study Report

Ariel, the Atmospheric Remote-sensing Infrared Exoplanet Large-survey, was adopted as the fourth medium-class mission in ESA's Cosmic Vision programme to be launched in 2029. During its 4-year mission, Ariel will study what exoplanets are made of, how they formed and how they evolve, by surveying a diverse sample of about 1000 extrasolar planets, simultaneously in visible and infrared wavelengths. It is the first mission dedicated to measuring the chemical composition and thermal structures of hundreds of transiting exoplanets, enabling planetary science far beyond the boundaries of the Solar System. The payload consists of an off-axis Cassegrain telescope (primary mirror 1100 mm x 730 mm ellipse) and two separate instruments (FGS and AIRS) covering simultaneously 0.5-7.8 micron spectral range. The satellite is best placed into an L2 orbit to maximise the thermal stability and the field of regard. The payload module is passively cooled via a series of V-Groove radiators; the detectors for the AIRS are the only items that require active cooling via an active Ne JT cooler. The Ariel payload is developed by a consortium of more than 50 institutes from 16 ESA countries, which include the UK, France, Italy, Belgium, Poland, Spain, Austria, Denmark, Ireland, Portugal, Czech Republic, Hungary, the Netherlands, Sweden, Norway, Estonia, and a NASA contribution

Applications de l'optique diffractive dans le domaine du traitement de l'information

Après une introduction résumant l'historique du mariage entre l'optique diffractive et le traitement de l'information, la synthèse d'optiques diffractives sera discuté, suivie par des exemples d'applications d'optique diffractive dans le domaine du traitement de l'information

A LATERAL SENSOR FOR THE ALIGNMENT OF TWO FORMATION-FLYING

The coarse lateral sensor is a system able to measure the lateral position between two satellites. It bridges the gap between the alignment accuracy achieved with the radio frequency metrology, and the alignment accuracy required the highprecision optical metrology (fine-lateral and longitudinal sensor). The coarse lateral sensor developed at Centre Spatial de Liège (CSL) is a standalone unit. Once connected to an unregulated 28V power-supply, it delivers, the lateral position of a corner cube retro-reflector (within an angle of 10 arcdeg and from 25 to 250 m) and tracks this position at a rate of 10 Hz. The system is operational with the sun in its fieldof- view. Real time centroidisation algorithms allow tracking the image position and feed the on-board computer with this information via a RS422 link, allowing further position stabilization. The coarse lateral sensor has successfully undergone thermal qualification (40°C and -30 °C), and vibration test (high-level sinus, random and shock test in the 3– axis)

Co-registration and complex interpolation

This paper presents a novel and efficient method, based on a modified version of the Chirp-Z transform algorithm, for performing the co-registration of SAR images as required in SAR interferometry. The method also allows complex interpolation of an entire image, by application, at each point of a bilinear coordinate transformation