ACRIMSAT (Active Cavity Radiometer Irradiance Monitor Satellite)

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 carries an instrument called ACRIM-3 (Active Cavity Radiometer Irradiance Monitor 3), which is the third in a series of long-term solar-monitoring tools built by JPL (Jet Propulsion Laboratory). This instrument extends 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 is part of NASA's EOS (Earth Observing System).

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

Related category

• SATELLITES AND SPACE PROBES

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