The Atmospheric Remote sensing Infrared Exoplanet Large survey (ARIEL) mission is an M-class mission candidate
within the science program Cosmic Vision of the European Space Agency (ESA). It was selected in June 2015 as one of
three candidates to enter an assessment phase (phase 0/A). This process involves the definition of science and mission
requirements as well as a preliminary model payload, and an internal Concurrent Design Facility (CDF) study providing
the input to parallel industrial studies (in progress since 2016). After this process, the three candidates will be reviewed
and in mid-2017 one of them will be selected as the M4 mission for launch in 2026.
ARIEL is a survey-type mission dedicated to the characterisation of exoplanetary atmospheres. Using the differential
technique of transit spectroscopy, ARIEL will obtain transmission and/or emission spectra of the atmospheres of a large
and diverse sample of known exoplanets (~500) covering a wide range of masses, densities, equilibrium temperatures,
orbital properties and host-star characteristics. This will include hot Jupiters to warm Super-Earths, orbiting M5 to F0
This paper describes critical requirements, and reports on the results of the Concurrent Design Facility (CDF) study that
was conducted in June / July 2015, providing a description of the resulting spacecraft design. It will employ a 0.7 m x 1.1
m off-axis three mirror telescope, feeding four photometric channels in the VNIR range (0.5-1.95 μm) and an IR
spectrometer covering 1.95-7.8 μm.