|Mission type||Solar astronomy|
|Operator||NASA / JPL|
|Mission duration||7 years|
|Launch mass||288 kilograms (635 lb)|
|Start of mission|
|Launch date||20 December 1999, 07:13UTC|
|Launch site||Vandenberg LC-576E|
|Semi-major axis||7,067.28 km (4,391.40 mi)|
|Perigee||675 km (419 mi)|
|Apogee||717 km (446 mi)|
|Epoch||5 December 2013, 12:18:57 UTC|
The Active Cavity Radiometer Irradiance Monitor Satellite, or ACRIMSAT is a dedicated satellite and instrument that is one of the 21 primary observational components of NASA's Earth Observing System program. ACRIMSAT was launched on 20 December 1999 from Vandenberg Air Force Base as the secondary payload on a Taurus rocket along with KOMPSAT and placed into a high inclination, 700 km. sun-synchronous orbit from which the ACRIM3 instrument monitors the total solar irradiance (TSI).
The ACRIM3 instrument has made state of the art measurements of the TSI since the start of its Science Mission in April 2000. It extends the TSI measurement database begun by earlier ACRIM instruments on the NASA Solar Maximum Mission (ACRIM1: 1980-1989) and Upper Atmosphere Research Satellite (ACRIM2: 1991-2001).
Richard C. Willson is the principal investigator for the experiment and leads the ACRIM3 Science Team. Willson designed the active cavity radiometer type of sensor used by self-calibrating satellite TSI monitoring experiments today. The implementation of the ACRIM3 instrument was a collaboration between Willson, the original JPL/ACRIMSAT Project Manager Ronald Zenone and ACRIM3 Instrument Scientist Roger Helizon. The Mission is controlled using the ACRIMSAT tracking station at the JPL Table Mountain Observatory in Southern California. Co-Investigators are: Nicola Scafetta (climate impact of solar variability), Hugh Hudson (solar physics)and Alexander Mordvinov (solar physics).
ACRIMSAT (international designator 1999-070B) is a spin-stabilized, single-purpose satellite constructed by Orbital Sciences Corporation. The end-to-end cost of the ACRIMSAT satellite, the ACRIM3 instrument, launch, ground station, operations and the science team activities during its 11 year mission to date has been less than $30 million - a good example of the efficacy of NASA's 'Better, Faster, Cheaper' initiative and ample evidence that inexpensive instrumentation and small dedicated satellites are the cost-effective approach for providing state-of-the-art TSI monitoring.
ACRIMSAT/ACRIM3 tracked the TSI during a 2004 transit of Venus, and measured the 0.1% reduction in the solar intensity caused by the shadow of the planet. It also recorded data for the 2012 Transit of Venus.
At 09:43 and at 11:21 on 5th of April 2014 ACRIMSAT was rated as having a high risk of collision (<20m) with the newly launched Sentinel-1A. A 39 second burn of Sentinel-1A during LEOP succesfully avoided the collision. 
- "ACRIMSAT Satellite details 1999-070B NORAD 26033". N2YO. 5 December 2013. Retrieved 6 December 2013.
- http://www.journals.uchicago.edu/cgi-bin/resolve?doi=10.1086/500427.html The Astrophysical Journal v.641 pp.565–571 (2006), Schneider, J. M. Pasachoff, and Richard C. Willson, The Effect of the Transit of Venus on ACRIM's Total Solar Irradiance Measurements: Implications for Transit Studies of Extrasolar Planets
- PIA15820: NASA's ACRIMSAT Observes Venus Transit
- Sentinel-1A team. "A NIGHT SHIFT LIKE NEVER BEFORE". ESA. Retrieved 17 April 2014.
- Press Kit
- ACRIM Science Team homepage
- ACRIMSAT Project homepage
- Fact sheet on the mission
- ACRIMSAT: NASA Science Missions