NASA to Decommission Tropical Rainfall Measuring Mission

Gretchen Cook-Anderson
Headquarters, Washington July 16, 2004
(Phone: 202/358-0836)

RELEASE: 04-230

NASA TO DECOMMISSION TROPICAL RAINFALL MEASURING MISSION

NASA will decommission the Tropical Rainfall Measuring
Mission (TRMM) later this year. A highly successful
scientific research mission, TRMM has provided data used
worldwide in the monitoring and forecasting of hazardous
weather on a demonstration basis. Originally intended to be a
three-year mission when launched in 1997, TRMM is now in its
seventh year of operation having completed all of its
research and technology objectives four years ago. The
extension of mission operations for nearly four additional
years was made possible through NASA's efficient management
of available resources, technical innovations, and
substantial additional funding.

"TRMM has been an outstanding example of scientific success
and U.S.-Japanese collaboration in conducting Earth
observations from space. The unique TRMM precipitation
observations have led to new knowledge concerning the Earth's
hydrological cycle and its variation," said NASA's Associate
Administrator for Earth Science Dr. Ghassem Asrar. "We now
look forward to continued cooperation with our Japanese
partners on the Global Precipitation Measurement mission,
that will build on the TRMM legacy," he added.

TRMM is the first mission dedicated to measuring tropical and
subtropical rainfall through microwave and visible infrared
sensors, including the first spaceborne rain radar. The
Precipitation Radar aboard TRMM is the first rain radar ever
to be launched into space. It measures precipitation
distributions over both land and sea. TRMM has exceeded
expectations for accuracy and resolution and has given
unprecedented insights into rainfall producing cloud systems
over tropical land masses and oceans.

In 1998 TRMM observed Hurricane Bonnie and captured for the
first time "sky scrapper" storm clouds towering some 59,000
feet above the ocean - an event scientists believe may have
represented a precursor to storm intensification.

In August 2001, TRMM was boosted from an altitude of 350 km
to a higher 402 km orbit to extend its life. This maneuver
successfully reduced atmospheric drag on the spacecraft
during a period of high solar activity and increased TRMM's
life by two years while maintaining the high quality of its
scientific observations. NASA also developed a technique to
extend TRMM's life by using atmospheric drag, rather than
fuel, to lower the spacecraft's altitude in the early stages
of the controlled de-orbit process. This scenario has
permitted TRMM to continue its normal operations since
November 2003.

NASA and the Japanese Space Program (JAXA) will continue
close collaboration by establishing a new advanced capability
for the measurement of precipitation globally with the Global
Precipitation Measurement mission (GPM). The partnership will
launch GPM's Core Satellite by the end of the decade.

This complex and pioneering international satellite
constellation is a prototype for the comprehensive,
coordinated, and sustained Earth observation system
envisioned by the international Group on Earth Observations
(GEO) framework. The GPM main satellite is planned to carry
advanced, dual-frequency radar that will exceed the
capabilities of TRMM's radar. This radar will be capable of
making measurements of light rain and frozen precipitation
present in higher latitudes in addition to the heavier rain
present in the tropics.

In addition, GPM will comprise an international constellation
of satellites to measure precipitation globally approximately
every three hours; TRMM is limited to conducting less
frequent observations at tropical latitudes. GPM will use an
extensive ground validation network to further improve the
accuracy of its measurements compared to those made by TRMM.

For more information about GPM on the Internet, visit:

http://gpm.gsfc.nasa.gov/

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