The Special Sensor Microwave Imager (SSM/I) instrument is carried aboard the Defense Meteorological Satellite Program (DMSP) satellites F8, F10, F11, and F13 as part of NASA's Polar Pathfinder Program. SSM/I coverage began August 1987 and continues through the present. The SSM/I is a seven-channel, four-frequency, orthogonally polarized, passive microwave radiometric system that measures atmospheric, ocean, and terrain microwave brightness temperatures at 19.35, 22.2, 37.0, and 85.5 GHz, with a spatial resolution of 25 km for the first three channels and 12.5 km for the 85 GHz channel.

The primary purpose of the SMM/I instrument is to measure sea surface temperature and near-surface winds under all weather conditions for developing and testing global ocean circulation models and other aspects of ocean dynamics. Additional parameters are also measured, such as ocean surface wind speed, area covered by ice, age of ice, ice edge, precipitation over land, cloud liquid water, integrated water vapor, precipitation over water, soil moisture, land surface temperature, and snow cover. In addition, brightness temperatures are computed from antenna temperatures using the published antenna pattern correction, which includes dynamic adjustments for antenna side lobe, antenna efficiencies, and neighboring pixel contributions.

NSIDC produces daily gridded brightness temperature data from orbital swath data derived from the SSM/I instrument. To obtain SSM/I data, please refer to the Passive Microwave Sea Ice Products Web page.