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

Advances in the development of a Mach-Zehnder interferometric Doppler imager for seismology of giant planets

International audienceThe measurements of radial velocity fields on planets with a Doppler Spectro-Imager allow the study of atmospheric dynamics of giant planets and the detection of their acoustic oscillations. The frequencies of these oscillations lead to the determination of the internal structure by asteroseismology. A new imaging tachometer, based on a Mach-Zehnder interferometer, has been developed to monitor the Doppler shift of solar lines reflected at the surface of the planets. We present the principle of this instrument. A prototype was designed and built, following the specifications of a future space mission. The performance of the prototype, both at the laboratory and on the sky, is presented here

MAJIS focal plane unit: performance of the IR channel filters

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Optical alignment of the Solar Orbiter EUI flight instrument

The Extreme Ultraviolet Imager (EUI) instrument for the Solar Orbiter mission will image the solar corona in the extreme ultraviolet (17.1 nm and 30.4 nm) and in the vacuum ultraviolet (121.6 nm). It is composed of three channels, each one containing a telescope. Two of these channels are high resolution imagers (HRI) at respectively 17.1 nm (HRI-EUV) and 121.6 nm (HRI-Ly∝), each one composed of two off-axis aspherical mirrors. The third channel is a full sun imager (FSI) composed of one single off-axis aspherical mirror and working at 17.1 nm and 30.4 nm alternatively. This paper presents the optical alignment of each telescope. The alignment process involved a set of Optical Ground Support Equipment (OGSE) such as theodolites, laser tracker, visible-light interferometer as well as a 3D Coordinates Measuring Machine (CMM). The mirrors orientation have been measured with respect to reference alignment cubes using theodolites. Their positions with respect to reference pins on the instrument optical bench have been measured using the 3D CMM. The mirrors orientations and positions have been adjusted by shimming of the mirrors mount during the alignment process. After this mechanical alignment, the quality of the wavefront has been checked by interferometric measurements, in an iterative process with the orientation and position adjustment to achieve the required image quality

Interstellar and interplanetary carbonaceous solids in the laboratory

International audienceThe interstellar medium (ISM) is a physico-chemical laboratory where extreme conditions are encountered and whereparticular environmental parameters (e.g., density, reactant nature, radiation, temperature, time scales) define the compositionof matter. With present observational possibilities, the fundamental question regarding the possible link betweenISM and solar system samples can be addressed by astrophysicists, planetologists, and cosmochemists. This article focuseson observations of diffuse ISM and dust components of molecular clouds, setting constraints on the composition oforganic solids and large molecules associated with matter cycling in the Galaxy. This study aims at drawing somecommonalities and differences between the materials found in the Solar System and those found in interstellar dust

MAJIS IR channel: 3) performance of the focal plane unit

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Beyond the disk: EUV coronagraphic observations of the Extreme Ultraviolet Imager on board Solar Orbiter

Context. Most observations of the solar corona beyond 2 R consist of broadband visible light imagery carried out with coronagraphs. The associated diagnostics mainly consist of kinematics and derivations of the electron number density. While the measurement of the properties of emission lines can provide crucial additional diagnostics of the coronal plasma (temperatures, velocities, abundances, etc.), these types of observations are comparatively rare. In visible wavelengths, observations at these heights are limited to total eclipses. In the ultraviolet (UV) to extreme UV (EUV) range, very few additional observations have been achieved since the pioneering results of the Ultraviolet Coronagraph Spectrometer (UVCS). Aims. One of the objectives of the Full Sun Imager (FSI) channel of the Extreme Ultraviolet Imager (EUI) on board the Solar Orbiter mission has been to provide very wide field-of-view EUV diagnostics of the morphology and dynamics of the solar atmosphere in temperature regimes that are typical of the lower transition region and of the corona. Methods. FSI carries out observations in two narrowbands of the EUV spectrum centered on 17.4 nm and 30.4 nm that are dominated, respectively, by lines of FeIX/X (formed in the corona around 1 MK) and by the resonance line of HeII (formed around 80 kK in the lower transition region). Unlike previous EUV imagers, FSI includes a moveable occulting disk that can be inserted in the optical path to reduce the amount of instrumental stray light to a minimum. Results. FSI detects signals at 17.4 nm up to the edge of its field of view (7 R), which is about twice further than was previously possible. Operation at 30.4 nm are for the moment compromised by an as-yet unidentified source of stray light. Comparisons with observations by the LASCO and Metis coronagraphs confirm the presence of morphological similarities and differences between the broadband visible light and EUV emissions, as documented on the basis of prior eclipse and space-based observations. Conclusions. The very-wide-field observations of FSI out to about 3 and 7 R, without and with the occulting disk, respectively, are paving the way for future dedicated instruments.ISSN:0004-6361ISSN:1432-074

MAJIS VIS-NIR channel: performances of the focal plane unit - flight model

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