Geostationary Interferometric Infrared Sounder-2

Geostationary Interferometric Infrared Sounder-2 is the FY-4B-class GIIRS sounder: a geostationary nadir MWIR/TIR interferometric infrared payload for temperature and humidity sounding and wind-profile derivation from water-vapour features ^[1][2]. It is a sounding instrument rather than an imager, with hyperspectral infrared channels for atmospheric profiling and a visible channel for cloud detection ^[1][3]. The FY-4B configuration covers LWIR 680-1130 cm^-1, MWIR 1650-2250 cm^-1, and a 0.55-0.90 um visible channel; in wavelength terms, that is roughly 8.85-14.7 um for LWIR, 4.44-6.06 um for MWIR, and 0.55-0.90 um visible context ^[1]. Ground sampling is 12 km at sub-satellite point for the infrared sounding channels and 1 km for the visible channel, with a 45 minute China-area cycle in the FY-4B characteristics ^[1]. The GIIRS-2 label also spans later FY-4 configurations in operational records, while the family characteristics separate FY-4A, FY-4B, and FY-4C values; FY-4C range, SNR, and spatial-resolution improvements remain tied to that later configuration rather than carried back into FY-4B-class GIIRS-2 ^[1][3].