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Active Cavity Radiometer Irradiance Monitor Satellite (ACRIMSAT)

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Status: Completed
Mission Category: Earth Observing System (EOS)
Launch Date: December 20, 1999
Launch Location: Vandenberg Air Force Base, CA

The Active Cavity Radiometer Irradiance Monitor Satellite (ACRIMSAT) was launched on December 20, 1999, as a secondary payload on a Taurus launch vehicle and carries the Active Cavity Radiometer Irradiance Monitor 3 (ACRIM3) instrument. The science mission began on April 5, 2000, following a period of on-orbit adjustment of the solar-pointing software on ACRIMSAT. The purpose of ACRIM3 is to study Total Solar Irradiance (TSI). ACRIM3, the third in a series of ACRIM solar-monitoring experiments built for NASA by the Jet Propulsion Laboratory (JPL), extends the database begun by ACRIM1, launched in 1980 on the Solar Maximum Mission (SMM) spacecraft, and continued by ACRIM2, launched on the Upper Atmosphere Research Satellite (UARS) in 1991. ACRIMSAT/ACRIM3 completed its five-year Minimum Mission in 2005.

In December 2013, ACRIMSAT suffered a mission-ending failure when its degrading batteries could no longer sustain operations.  The spacecraft has not responded to ground commands since December 14, 2013.  After several unsuccessful recovery attempts and extensive failure analysis, the mission was determined to be unrecoverable and officially terminated July 30, 2014.  

ACRIMSAT lasted nearly 13 years, more than twice as long as originally designed, and delivered a dataset that exceeded mission requirements, making it an unqualified success.  The dataset will receive a final reprocessing using updated laboratory characterizations of all 3 ACRIM sensors; the reprocessed dataset will be available to researchers beginning August 2015. This more than 3 decade long data series exceeds the duration of any other irradiance instruments.

Key Active Cavity Radiometer Irradiance Monitor Satellite Facts

Mission/Portal Page:
Altitude:Distance from sea level. 720km
Inclination: 98.1°
Local Node:Approximate time, at the equator when vehicle is directly overhead. 10:00 a.m.
Instruments: ACRIM3 (Active Cavity Radiometer Irradiance Monitor)
Project Scientist(s): Richard C. Willson

Relevant Science Focus Areas:

  • Climate Variability and Change
  • Weather Water and Energy Cycle

Relevant Science Questions:

  • How does the Earth system respond to natural and human-induced changes?
  • How is the global Earth system changing?
  • How will the Earth system change in the future?

Science Goals:

  • Extend the TSI observational database with maximum precision and traceability.
  • With ACRIM3 results, relate past and future TSI databases using comparisons with the UARS/ACRIM2 experiment, the Solar Heliospheric Observatory (SOHO)/Variability of Solar Irradiance and Gravity Oscillations (VIRGO) experiment, and the Solar Radiation and Climate Experiment (SORCE)/Total Irradiance Monitor (TIM) experiment.
  • Develop a composite TSI time series incorporating results from satellite TSI observations since 1978.
  • Investigate the multidecadal upward TSI trend during solar cycles 21-23 using ACRIM3 observations of the solar activity minimum preceding cycle 24.
  • Provide a redundant monitoring capability to prevent catastrophic loss of the TSI longterm database in the event of a SORCE/TIM experiment failure.

Related Applications:

  • Carbon Management
  • Energy Management
  • Public Health