TRMM mast

TRMM path across the Pacific Ocean - Cyclone Susan was east of Australia The Tropical Rainfall Measuring Mission, TRMM, is the first mission dedicated to measuring tropical and subtropical rainfall.

Measurements from TRMM are used to find out where it's raining, and how hard it's raining. Not all clouds cause rain, and when rain does fall, it falls through various heights in the atmosphere, sometimes not reaching the ground at all!

Because rain is so variable, we have never known before just how much rain actually falls across the earth, but it is something we need to know if we are going to be able to predict wind patterns and ocean currents, floods and droughts.

TRMM won't be used for the daily rainfall measurements in your city, but it will be used by atmospheric scientists and weather forecasters to understand better how rainfall happens and why, so they can improve their forecasts in the future.

Fly "through" cyclone Susan, a recent hurricane in the Pacific, and see where the rain bands are in relation to the eye of the hurricane. In both the movie and in the picture of Hurricane Mitch, the color red indicates the areas with the most rain. (Quicktime movie 2.3 MB)


  • Precipitation Radar (PR)
  • TRMM Microwave Imager (TMI)
  • Visible Infrared Scanner (VIRS)
  • Clouds and the Earths Radiant Energy System (CERES)
  • Lightning Imaging Sensor (LIS)
A drawing of the orbital path for the TRMM satellite. The TRMM orbit is circular and is at an altitude of 218 nautical miles (350 km) and an inclination of 35 degrees to the Equator.

The spacecraft takes about 91 minutes to complete one orbit around the Earth. This orbit allows for as much coverage of the tropics and extraction of rainfall data over the 24-hour day (16 orbits) as possible.

Mission Time (GMT)
Javascript Required

Infrared and visible composite image of rain bands in hurricane
Hurricane Mitch over the Gulf of Mexico. Click the image to navigate to the TRMM image archives.
Launch Date
November 27, 1997

Operational Period
Continuing mission.
(Three year mission planned.)

Launch Vehicle
Model H-II Launch Vehicle

Launch Site
Japan's Tanegashima Space Center

Weather Satellite

What happened in the world the day TRMM was launched?

Where is TRMM now?

Try your skill at finding words in a word puzzle about TRMM. (Java Required).

Updated: January 22, 2003