High resolution infrared radiation sounder
From AMS Glossary
High Resolution Infrared Radiation Sounder
(Abbreviated HIRS.) One of three sounders that comprise the TIROS Operational Vertical Sounder package on NOAA polar orbiter satellites.
HIRS-2, derived from the experimental HIRS-1, which flew on ''Nimbus'' 6 launched in June 1975, measures incident radiation in 1 visible and 19 infrared spectral regions, with a nadir resolution of 17 km.