To be launched on Dec. 19, it will continue NASA's effort to determine whether an increasing trend in solar radiation discovered by recent experiments is continuing and contributing to a rise in global temperatures.

Although the sun's 11-year radiation change during a solar cycle is fairly well understood, small changes in the sun's overall output may have a significant role in global warming and other climatic changes on both shorter and longer time scales.

These range from El Ninos and La Ninas, on time scales of about two years, to little ice ages, on time scales of about 200 years. The Active Cavity Radiometer Irradiance Monitor (ACRIM) measures the sun's total energy output over time with state-of-the-art precision and will provide climatologists with data to improve their climate models and ability to make predictions over the next century.

"Small, sustained changes in total solar output of as little as 0.25 percent per century could become the primary cause of significant climate change on time scales of many decades," said Richard Willson, the experiment's principal investigator, who is based at Columbia's Center for Climate Systems research in Coronado, Calif. "The information we receive from this will be critical to understanding Earth's present climate and the possibility of climatic changes and global warming in the long-term."

This project is the third in a series of ACRIM satellite experiments to monitor solar variability in order to understand the radiation that creates the winds, heats the land, and drives the ocean currents. Results from the first two, launched in 1980 and 1991, indicate a subtle upward trend in total solar irradiance over the two decades.

The ACRIM III instrument is the sole payload of a small, 253-pound ACRIMSAT satellite that will be launched into circular orbit 425 miles above Earth by a Taurus commercial launch vehicle on Dec. 19. It always points toward the sun, and takes only 98 minutes to travel around Earth once. NASA's Jet Propulsion Laboratory (JPL) Pasadena, CA, built the ACRIM III instrument to the specifications of Willson, who directs all science operations. Orbital Sciences Corporation (OSC) provided the ACRIMSAT satellite and Taurus launch vehicle under contract to JPL.

Co-investigators include James Hansen, director of NASA/Goddard Institute for Space Studies, Alexander Mordvinov, Institute of Solar Terrestrial Physics, Russian Academy of Sciences, and Hugh Hudson, University of Calif. at San Diego.

The total cost of the experiment, including the instrument, satellite, launch and five-year science mission is under $30 million. It will launch about two years after project startup and represents a new paradigm for small experiments in NASA's effort to maximize science return per tax dollar spent in their "better, faster, cheaper" research efforts.

Columbia University

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Satellite Launch To Boost DTH In India
Calcutta, India (SPX) Dec 28, 2005
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