ACRIMSAT measured Total Solar Irradiance (TSI) during its primary five-year mission. The instrument, third in a series of long-term solar-monitoring tools built for NASA by the Jet Propulsion Laboratory, will continue to extend the database first created by ACRIM I, which was launched in 1980 on the Solar Maximum Mission (SMM) spacecraft. ACRIM II followed on the Upper Atmosphere Research Satellite (UARS) in 1991.

The Active Cavity Radiometer Irradiance Monitor (ACRIM) I instrument was the first to clearly demonstrate that the total radiant energy from the sun was not a constant. However, the solar variability was so slight (0.1% of full scale) that continuous monitoring by state-of-the-art instrumentation was necessary. It is theorized that as much as 25% of the anticipated global warming of the earth may be solar in origin. In addition, seemingly small (0.5%) changes in the TSI output of the sun over a century or more may cause significant climatological changes on Earth.

ACRIMSAT measured Total Solar Irradiance (TSI) during its primary five-year mission. The instrument, third in a series of long-term solar-monitoring tools built for NASA by the Jet Propulsion Laboratory, will continue to extend the database first created by ACRIM I, which was launched in 1980 on the Solar Maximum Mission (SMM) spacecraft. ACRIM II followed on the Upper Atmosphere Research Satellite (UARS) in 1991.

The Active Cavity Radiometer Irradiance Monitor (ACRIM) I instrument was the first to clearly demonstrate that the total radiant energy from the sun was not a constant. However, the solar variability was so slight (0.1% of full scale) that continuous monitoring by state-of-the-art instrumentation was necessary. It is theorized that as much as 25% of the anticipated global warming of the earth may be solar in origin. In addition, seemingly small (0.5%) changes in the TSI output of the sun over a century or more may cause significant climatological changes on Earth.