https://cdn.earthdata.nasa.gov/conduit/upload/5182/KeywordsCommunityGuide_Baseline_v1_SIGNED_FINAL.pdf 23.6 2026-03-19T10:41:57.720Z https://gcmd.earthdata.nasa.gov/KeywordViewer/scheme/instruments/7cac33c5-a557-4fee-b564-000c5e7f2817 GMI The Global Precipitation Measurement (GPM) Microwave Imager (GMI) instrument is a multi-channel, conical- scanning, microwave radiometer serving an essential role in the near-global-coverage and frequent-revisit-time requirements of GPM. The instrumentation enables the Core spacecraft to serve as both a 'precipitation standard' and as a 'radiometric standard' for the other GPM constellation members. The GMI is characterized by thirteen microwave channels ranging in frequency from 10 GHz to 183 GHz. In addition to carrying channels similar to those on the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI), the GMI carries four high frequency, millimeter-wave, channels about 166 GHz and 183 GHz. With a 1.2 m diameter antenna, the GMI will provide significantly improved spatial resolution over TMI. Scan Geometry:The off-nadir-angle defining the cone swept out by the GMI is set at 48.5 degrees which represents an earth- incidence-angle of 52.8 degrees. To maintain similar geometry with the predecessor TMI instrument, the-earth- incidence angle of GMI was chosen identical to that of the TMI. Rotating at 32 rotations per minute, the GMI will gather microwave radiometric brightness measurements over a 140 degree sector centered about the spacecraft ground track vector. The remaining angular sector is used for performing calibration; i.e. observation of cold space as well as observation of a hot calibration target.The 140 degree GMI swath represents a swath of 904 km on the Earth's surface. For comparison, the DPR instrument is characterized by cross-track swath widths of 245 km and 120 km, for the Ku and Ka-band radars respectively. Only the central portions of the GMI swath will overlap the radar swaths (and with approximately 67 second duration between measurements due to the geometry and spacecraft motion). These measurements within the overlapped swaths are important for improving precipitation retrievals, and in particular, the radiometer-based retrievals. Summary provided by http://pmm.nasa.gov/GPM/flight-project/GMIGroup: Instrument_Details Entry_ID: GMI Group: Instrument_Identification Instrument_Category: Earth Remote Sensing Instruments Instrument_Class: Passive Remote Sensing Instrument_Type: Spectrometers/Radiometers Instrument_Subtype: Imaging Spectrometers/Radiometers Short_Name: GMI Long_Name: Global Precipitation Measurement Microwave Imager End_Group Group: Associated_Platforms Short_Name: GPM End_Group Group: Spectral_Frequency_Information Wavelength_Keyword: Microwave Number_Channels: 13 Spectral_Frequency_Coverage_Range: 10 GHz to 183 GHz. End_Group Online_Resource: http://pmm.nasa.gov/GPM/flight-project/GMI Creation_Date: 2009-04-29 Group: Instrument_Logistics Instrument_Owner: USA/NASA End_GroupEnd_Group