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Instrument: TMI : TRMM Microwave Imager
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Associated Platforms

Spectral/Frequency Information
Wavelength Keyword: Microwave
Number Channels: 9
Spectral/Frequency Coverage/Range: 10.65, 19.35, 37.0, and 85.5 GHz at dual polarization and 22.235 GHz at vertical polarization
Spectral/Frequency Resolution: 37 to 4.6-km resolution respectively, covering 760-km swath

Related Data Sets
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The TRMM Microwave Imager (TMI) is an instrument on the Tropical Rainfall Measuring Mission (TRMM) Satellite which was launched on November 27, 1997 from the Tanegashima Space Center in Japan. The TMI, designed for NASA by Hughes, is a five-channel, dual-polarized, passive microwave radiometer. Microwave radiation is emitted by the Earth's surface and by water droplets within clouds. However, when layers of large ice particles are present in upper cloud regions - a condition highly correlated with heavy rainfall - microwave radiation tends to scatter. The TMI will detect radiation at five frequencies chosen to discriminate among these processes, thus revealing the likelihood of rainfall. The key to accurate retrieval of rainfall rates by this method is the deduction of cloud precipitation consistent with the radiation measurement at each frequency. The TMI data, supported by PR data, will be the primary data set of precipitation measurement.

TMI is a passive microwave radiometer designed to provide quantitative rainfall information over a wide swath. By carefully measuring the minute amounts of microwave energy emitted by Earth and its atmosphere, TMI is able to quantify the water vapor, the cloud water, and the rainfall intensity in the atmosphere. It is a relatively small instrument that consumes little power. This, combined with the wide swath and the good, quantitative information regarding rainfall, makes TMI the workhorse of the rain-measuring package on TRMM.

The average operating altitude for TRMM was changed from 350 to 403 km during the period of August 7-24, 2001. This orbit boost maneuver extended the mission life significantly. All post-boost data products had been released by the TRMM Science Project, as of early December 2001. All TRMM data products (post- and pre-boost) are available via the TRMM data search-and-order system at
The time period before August 7, 2001 is referred to as pre-boost, and the time period after August 24, 2001 is referred to as post-boost.

NASA Earth Science Reference Handbook [ Mission: TRMM ]

Online Resources

Instrument Logistics
Data Rate: 8.5 Kbps
Instrument Start Date: 1997-12-08
Instrument Owner: USA/NASA