ACRIMSAT was a satellite equipped to measure the amount of energy given out by the Sun – the total solar irradiance (TSI) – over a five-year period. ACRIMSAT carried an instrument called ACRIM-3 (Active Cavity Radiometer Irradiance Monitor 3), which was the third in a series of long-term solar-monitoring tools built by JPL (Jet Propulsion Laboratory). This instrument extended the database started by ACRIM-1, launched on SMM (Solar Maximum Mission) in 1980, and continued by ACRIM-2 on UARS (Upper Atmosphere Research Satellite) in 1991.

 

ACRIM-1 was the first experiment to show clearly that the TSI varies. The solar variability is so slight, however, that its study calls for continuous state-of-the-art monitoring. Theory suggests that as much as 25% of Earth's global warming may be of solar origin. It also seems that even small (0.5%) changes in the TSI over a century or more may have significant climatic effects. ACRIMSAT was part of NASA's EOS (Earth Observing System). Contact with the satellite was lost on 14 December 2013.

 

launch date	Dec 21, 1999
launch vehicle	Taurus
launch site	Vandenberg Air Force Base
orbit	272 km × 683 km × 98.3°