Active Cavity Radiometer Irradiance Monitor
Active Cavity Radiometer Irradiance Monitor ( ACRIM ) is a powerful instrument developed and manufactured for NASA by the Jet Propulsion Laboratory (JPL), a division of the California Institute of Technology (Caltech), for observing energy radiation from the sun , also known as Total Solar Irradiance (TSI ), and the fluctuations that occur in it.
To date, the instrument has been used in three missions:
- ACRIM-I , the first version of the instrument, was used for the Solar Maximum Mission (SMM) launched in 1980 . This instrument clearly proved that the energy radiated from the sun is not constant.
- ACRIM-II contributed to the Upper Atmosphere Research Satellite (UARS) mission and weighed approximately 26 kilograms .
- ACRIM-III represents the heart of the Active Cavity Radiometer Irradiance Monitor Satellite (ACRIMSat), which was launched in 1999 and is still active today . Further development has made it possible to reduce the weight by half and this version only weighs 13 kilograms.
The measurements of the total radiation of the sun by the ACRIM instruments will be continued by the satellite observatory SORCE .