Artist's concept of NASA's Active Cavity Radiometer Irradiance Monitor satellite, or ACRIMSAT, was launched in December 1999.

The Active Cavity Irradiance Monitor Satellite, or ACRIMSAT, mission is a climate change investigation that measures changes in how much of the sun's energy reaches Earth's atmosphere. This energy, called solar irradience, creates winds, heats the land and drives ocean currents, and therefore contains significant data that climatologists can use to improve predictions of climate change and global warming.

The satellite's Active Cavity Irradiance Monitor III instrument, now in its third generation, has been used since the 1980s to study solar irradiance and its impacts on global warming. Scientists, using data from the instrument, now theorize that there is a significant correlation between solar radiation and global warming.

ACRIMSAT completed its five-year primary mission in 2005 when it began operating under its extended mission.

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