MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov

Alan Buis (818) 354-0474
Jet Propulsion Laboratory, Pasadena, Calif.

Erica Hupp/Dolores Beasley (202) 358-1237/1753
NASA Headquarters, Washington, D.C.

News Release: 2005-081 May 20, 2005

NASA's AcrimSat Solar Spacecraft Completes Five-Year Mission

A NASA satellite that measures the variability in the amount
of the Sun's energy that reaches Earth's atmosphere and
impacts our winds, land and oceans has successfully
accomplished its five-year primary mission.

The Active Cavity Radiometer Irradiance Monitor satellite,
or AcrimSat, which was launched in December 1999, carries
the Acrim III instrument. The instrument is the third
in a series of solar-monitoring tools built by NASA's Jet
Propulsion Laboratory, Pasadena, Calif., and launched over
the past 25 years. The goal is to study the Sun-Earth
connection by measuring solar irradiance, the Sun's energy
that reaches our planet.

Scientists use data from the instruments to learn how solar
energy affects Earth's winds, heats the land, and drives
ocean currents, all of which affect Earth's weather and
climate. The data help researchers create global climate
models and study solar physics.

The experiments also found a drastic drop in solar
irradiance levels when Venus transited between the Earth and
Sun in June 2004. The decrease was equivalent to all the
energy used by humans in 2003.

"The satellite's measurements of total solar irradiance have
been the most precise ever collected," said Roger Helizon,
AcrimSat project manager/scientist at JPL. "The mission
has provided a wealth of data for its relatively small cost
of 30-million dollars."

More information on the mission is available at

http://acrim.jpl.nasa.gov .

AcrimSat is funded by NASA through the Earth Science Programs
Office at NASA's Goddard Space Flight Center, Greenbelt, Md.
The AcrimSat project office at JPL managed the design,
fabrication, and test of the Acrim III instrument and the
subcontract for the spacecraft, built by Orbital Sciences
Corporation, Dulles, Va. The spacecraft is controlled by a
dedicated ground station located at JPL's Table Mountain
Facility in Wrightwood, Calif. JPL is managed for NASA by
the California Institute of Technology in Pasadena.

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