[′sad·əl‚īt ¦in·frə′red spek′träm·əd·ər] (spectroscopy) A spectrometer carried aboard satellites in the Nimbus series which measures the radiation from carbon dioxide in the atmosphere at several different wavelengths in the infrared region, giving the vertical temperature structure of the atmosphere over a large part of the earth. Abbreviated SIRS.AcronymsSeeSIRS