GMI Overview

The Global Precipitation Measurement (GPM) satellite contains the GPM Microwave Imager (GMI), which gathers information about soil moisture on the Earth's surface. GPM takes measurements from 407 km above Earth's surface, which when combined with a 1.22 m antenna allows for swath widths of 931 km at very high resolutions.

The GMI is a passive, conically-scanning, and multi-channel microwave radiometer. These microwaves range in frequency from 10 GHz to 183 GHz. Noise diodes for the low frequency channels allow for better calibration of the instrument, giving highly accurate readings. These low frequency channels also have large footprints with enough overlap to create complete coverage.

The off-nadir-angle that creates the cone is set to 48.5 degrees, which represents an Earth incidence angle of 52.8 degrees. The Earth viewing scan sector is about 140 degrees and is centered along the velocity vector. The remaining 260 degrees is used for housekeeping and instrument calibration.

The above information, as well as additional information can be found at https://directory.eoportal.org/web/eoportal/satellite-missions/g/gpm and https://pmm.nasa.gov/gpm/flight-project/gmi