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.