Ariel [1] is the M4 mission of the ESA’s Cosmic Vision Program 2015-2025, whose aim is to characterize by lowresolution transit spectroscopy the atmospheres of over one thousand warm and hot exoplanets orbiting nearby stars. The operational orbit of the spacecraft is baselined as a large amplitude halo orbit around the Sun-Earth L2 Lagrangian point, as it offers the possibility of long uninterrupted observations in a fairly stable radiative and thermo-mechanical environment. A direct escape injection with a single passage through the Earth radiation belts and no eclipses is foreseen. The space environment around Earth and L2 presents significant design challenges to all spacecraft, including the effects of interactions with Sun radiation and charged particles owning to the surrounding plasma environment, potentially leading to dielectrics charging and unwanted electrostatic discharge (ESD) phenomena endangering the Payload operations and its data integrity. Here, we present some preliminary simulations and analyses about the Ariel Payload dielectrics and semiconductors charging along the transfer orbit from launch to L2 included.
This paper describes the Optical Ground Support Equipment (OGSE) that is being developed for the payload level testing of the Ariel Space Telescope. Ariel has been adopted as ESA’s “M4” mission in its Cosmic Visions Programme and will launch in 2029 to the second Earth-Sun Lagrange point. During four years of operation the Ariel payload (PL – the cryogenic payload module plus warm units) will perform precise transit spectroscopy of approximately 1000 known exoplanetary atmospheres using a 1.1 m × 0.7 m telescope coupled to two instruments: the Fine Guidance Sensor (FGS) and the Ariel Infrared Spectrometer (AIRS). These instruments provide three spectrometric channels that cover 1.0 to 7.8 μm wavelength range and three photometric channels between 0.5 and 1.1 μm. The Ariel OGSE will verify the optical and radiometric performance of the integrated Ariel PL under vacuum and cryogenic (<40 K) test conditions within the limitations of operation under Earth’s gravity and vibration environments. To achieve these verification requirements the OGSE is integrated with the main Ariel ground test 5 m thermal vacuum chamber. The test chamber contains a cryogenic enclosure (the Cryogenic Test Rig) that surrounds the PL and the OGSE itself comprises of four subsystems. (1) A cryogenic vacuum chamber and integrating sphere illumination module that is fed by visible, near infrared and thermal infrared sources. The illumination module is mounted external to the Ariel test chamber and coupled via a vacuum feedthrough that relays a 22 mm diameter test beam into the Cryogenic Test Rig. The test beam is then relayed using (2) an injection module that steers the beam to maintain alignment during cool-down and scan the Ariel telescope field of view. The beam is then expanded to partially illuminate the Ariel telescope primary mirror using an (3) ~0.3 m diameter target projector collimating mirror. The final optical component of the OGSE is a (4) beam expander placed on the Ariel common optical bench to compensate for the sub-aperture illumination of the primary and to ensure that the spectrometer modules provide illumination with correct cone angles during ground testing. It is planned to use the OGSE in 2026 for a full range of calibration and verification tests of the end-to-end telescope and instrument performance, including detectors, field of view and alignment. These tests will then ensure that Ariel meets it challenging photometric and spectral performance requirements.
Ariel (Atmospheric Remote-Sensing Infrared Exoplanet Large Survey) is the adopted M4 mission of ESA “Cosmic Vision” program. Its purpose is to conduct a survey of the atmospheres of known exoplanets through transit spectroscopy. Launch is scheduled for 2029. Ariel scientific payload consists of an off-axis, unobscured Cassegrain telescope feeding a set of photometers and spectrometers in the waveband between 0.5 and 7.8 µm, and operating at cryogenic temperatures. The Ariel Telescope consists of a primary parabolic mirror with an elliptical aperture of 1.1 m of major axis, followed by a hyperbolic secondary, a parabolic recollimating tertiary and a flat folding mirror directing the output beam parallel to the optical bench. The secondary mirror is mounted on a roto-translating stage for adjustments during the mission. Proper operation of the instruments prescribes a set of tolerances on the position and orientation of the telescope output beam: this needs to be verified against possible telescope misalignments as part of the ongoing Structural, Thermal, Optical and Performance Analysis. A specific part of this analysis concerns the mechanical misalignments, in terms of rigid body movements of the mirrors, that may arise after ground alignment, and how they can be compensated in flight. The purpose is to derive the mechanical constraints that can be used for the design of the opto-mechanical mounting systems of the mirrors. This paper describes the methodology and preliminary results of this analysis, and discusses future steps.
AIRS is the infrared spectroscopic instrument of ARIEL: Atmospheric Remote‐sensing Infrared Exoplanet Large‐survey mission selected in March 2018 as the Cosmic Vision M4 ESA mission and planned to be launched in 2029 by an Ariane 6 from Kourou toward a large amplitude orbit around L2 for a 4 year mission. Within the scientific payload, AIRS will perform transit spectroscopy of over a 1000 of exoplanets to complete a statistical survey, including gas giants, Neptunes, super-Earths and Earth-size planets around a wide range of host stars. All these collected spectroscopic data will be a major asset to answer the key scientific questions addressed by this mission: what are the exoplanets made of? How do planets and planetary system form? How do planets and their atmospheres evolve over time? The AIRS instrument is based on two independent channels covering the CH0 [1.95-3.90] µm and the CH1 [3.90-7.80] µm wavelength range with prism-based dispersive elements producing spectrum of low resolutions R<100 in CH0 and R<30 in CH1 on two independent detectors. The spectrometer is designed to provide spectrum Nyquist-sampled in both spatial and spectral directions to limit the sensitivity of measurements to the jitter noise and intra pixels pattern during the long (10 hours) transit spectroscopy exposures. A full instrument overview will be presented covering the thermal mechanical design of the instrument functioning in a 60 K cold environment, up to the detection and acquisition chain of both channels based on 2 HgCdTe detectors actively cooled down below 42 K. This overview will present updated information of phase B2 studies in particular with the early manufacturing of prototype for key elements like the optics, focal-plane assembly and read-out electronics as well as the results of testing of the IR detectors up to 8.0 μm cut-off.
ARIEL, the Atmospheric Remote-sensing Infrared Exoplanet Large-survey mission1-3 was selected in early 2018 by the European Space Agency (ESA) as the fourth medium-class mission (M4) launch opportunity of the Cosmic Vision Program, with an expected launch in late 2028. It is the first mission dedicated to the analysis of the chemical composition and thermal structures of up to a thousand transiting exoplanets atmospheres, which will expand planetary science far beyond the limits of our current knowledge.
The Atmospheric Remote-Sensing Infrared Exoplanet Large-survey, ARIEL, has been selected to be the next (M4) medium class space mission in the ESA Cosmic Vision programme. From launch in 2028, and during the following 4 years of operation, ARIEL will perform precise spectroscopy of the atmospheres of ~1000 known transiting exoplanets using its metre-class telescope. A three-band photometer and three spectrometers cover the 0.5 µm to 7.8 µm region of the electromagnetic spectrum.
This paper gives an overview of the mission payload, including the telescope assembly, the FGS (Fine Guidance System) - which provides both pointing information to the spacecraft and scientific photometry and low-resolution spectrometer data, the ARIEL InfraRed Spectrometer (AIRS), and other payload infrastructure such as the warm electronics, structures and cryogenic cooling systems.
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