The Atmospheric Infrared Sounder (AIRS) is a grating spectrometer (R = 1200) aboard the second Earth Observing System (EOS) polar-orbiting platform, EOS Aqua. In combination with the Advanced Microwave Sounding Unit (AMSU) and the Humidity Sounder for Brazil (HSB), AIRS constitutes an innovative atmospheric sounding group of visible, infrared, and microwave sensors. The AIRS Infrared (IR) level 1B data set contains AIRS calibrated and geolocated radiances in milliWatts/m^2/cm^-1/steradian for 2378 infrared channels in the 3.74 to 15.4 micron region of the spectrum. The AIRS Level 1B product consists of calibrated radiances, geolocation coordinates, quality control parameters, and calibration engineering support information. This product converts the AIRS raw data in digital counts to radiances referenced to SI (Système international) traceable standards established at NIST for each of the 2378 AIRS channels, and contains ancillary information pertaining to the instrument calibration and performance. In general, the differences between the previous version, V5, and V8 are extremely small and not significant for most applications, however the improvements may have relevance for certain climate applications. The differences also make the product more versatile and contains more information about the calibration that will be useful for future modifications. More information can be found in the AIRS Version 8 Level 1B ATBD and Test Report.
The AIRS instrument is co-aligned with AMSU-A so that successive blocks of 3 x 3 AIRS footprints are contained within one AMSU-A footprint. The AIRSAQIRL1B_8 products are stored in files (often referred to as "granules") that contain 6 minutes of data, 90 footprints across track by 135 lines along track.