The Imaging Infrared Radiometer (IIR) aboard the joint NASA/French Space Agency Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite is a nadir-viewing, non-scanning radiometer that acquires measurements in three thermal infrared channels: 8.7 µm, 10.5 µm, and 12.0 µm. These wavelengths optimize retrievals of cirrus cloud emissivity and particle size. IIR and CALIPSO's Cloud and Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument work together to sample the same cloud – while IIR retrieves layer-average cloud properties, CALIOP samples the same 1 km IIR pixel to acquire vertical profiles of cloud layers.
