Planning the integration and test of a space telescope with a 1 m aluminum primary mirror: the Ariel mission case

Abstract

Ariel (Atmospheric Remote-Sensing Infrared Exoplanet Large Survey) is ESA's M4 mission of the "Cosmic Vision" program, with launch scheduled for 2029. Its purpose is to conduct a survey of the atmospheres of known exoplanets through transit spectroscopy.Ariel is based on a 1 m class telescope optimized for spectroscopy in the waveband between 1.95 and 7.8 µm, operating at cryogenic temperatures in the range 40-50 K. The Ariel Telescope is an off-axis, unobscured Cassegrain design, with a parabolic recollimating tertiary mirror and a flat folding mirror directing the output beam parallel to the optical bench. The secondary mirror is mounted on a rototranslating stage for adjustments during the mission. The mirrors and supporting structures are all realized in an aerospace-grade aluminum alloy T6061 for ease of manufacturing and thermalization. The low stiffness of the material, however, poses unique challenges to integration and alignment.