View Instrument

Instrument Type: sounder, Operational Mode: cross-track, Collection Type: continuous scan, Other Information: The HIRS/4 instrument provides multispectral data from one visible channel (0.69 m), seven shortwave channels (3.7 to 4.6 m) and twelve longwave channels (6.7 to 15 m) using a single telescope and a rotating filter wheel containing twenty individual spectral filters. An elliptical scan mirror provides cross-track scanning of 56 steps in increments of 1.8 degrees. The mirror steps rapidly (<35 msec), then holds at each position while the optical radiation , passing through the 20 spectral filters, is sampled. This action takes place each 0.1 second. The instantaneous field of view for each channel is approximately 0.7 degrees which, from a spacecraft altitude of 833 km, encompasses a circular area of 10 km at nadir on the earth.