The AERI is a passive remote sounding instrument, employing a Fourier transform
spectrometer operating in the spectral range 3.3–19.2 µm (520–3020 cm-1)
at an unapodized resolution of 0.5 cm-1 (max optical path difference of 1 cm).
The extended range AERIs (ER-AERI) deployed in dry climates (e.g. the Arctic) have a
spectral range of 3.3–25.0 µm (400–3020 cm-1) that allow measurements in the
far-infrared region. Two detectors are used, an HgCdTe and an InSb, cooled to cryogenic
temperatures, to cover these spectral ranges. The instrument has a zenith angular
field-of-view of 46 mrad full angle. The AERI absolute radiometric accuracy is designed
to be better than 1% of the radiance of a blackbody at surface ambient temperature.
This level of absolute accuracy is important for climate applications as well as for
products derived from AERI radiances. The radiometric accuracy is ensured by regular
calibration views of two high-quality blackbodies: the Hot Blackbody (HBB) is temperature
controlled to 333 K; the Ambient Blackbody (ABB) passively follows ambient temperature.
The AERI averages views of the sky over a 16 second interval; The AERI operates continuously
and a sky view is taken approximately every 20 seconds.