  The Atmospheric Remote-sensing Infrared Exoplanet Large-survey mission
(ARIEL) is one of the three present candidates for the ESA M4 (the fourth
medium mission) launch opportunity. The proposed Payload will perform a large
unbiased spectroscopic survey from space concerning the nature of exoplanets
atmospheres and their interiors to determine the key factors affecting the
formation and evolution of planetary systems. ARIEL will observe a large number
(>500) of warm and hot transiting gas giants, Neptunes and super-Earths around
a wide range of host star types, targeting planets hotter than 600 K to take
advantage of their well-mixed atmospheres. It will exploit primary and
secondary transits spectroscopy in the 1.2-8 um spectral range and broad-band
photometry in the optical and Near IR (NIR). The main instrument of the ARIEL
Payload is the IR Spectrometer (AIRS) providing low-resolution spectroscopy in
two IR channels: Channel 0 (CH0) for the 1.95-3.90 um band and Channel 1 (CH1)
for the 3.90-7.80 um range. It is located at the intermediate focal plane of
the telescope and common optical system and it hosts two IR sensors and two
cold front-end electronics (CFEE) for detectors readout, a well defined process
calibrated for the selected target brightness and driven by the Payload's
Instrument Control Unit (ICU).
