High Spectral Resolution Sounding with the Atmospheric Infrared Sounder (AIRS)

AIRS is a high spectral resolution instrument consisting of two pupil imaging, multi-aperture grating spectrometers which provide contiguous spectral coverage from 3.4 to 15.4 μ m, corresponding to 649 - 2941 cm -1 , at a resolving power of 1200. The short-wave spectrometer covers 3.4 - 8 μ m and the long-wave spectrometer 8 - 15.4 μ m. An optical schematic diagram of the spectrometer concept is shown in Figure 1. In addition to the IR spectrometers, the AIRS instrument contains six visible and near IR channels defined by bandpass filters. Every 2.667 seconds, AIRS will scan a ±49.5 degree swath across nadir in a direction perpendicular to the EOS satellite's ground track. The AIRS IFOV is 1.1 degree, providing a 13.5 km footprint at nadir from a 705 km orbital altitude. AIRS focal planes are comprised of linear arrays of mercury cadmium telluride (HgCdTe) detectors cooled to 60 K by a pair of split Sterling cycle coolers. The AIRS instrument will provide the capability to measure nominal scene radiances with a NEAT sensitivity of less than 0.2 K over most of the spectral band.