Active Cavity Radiometer Irradiance Monitor Satellite

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ACRIMSat
ACRIMSat
Type: Research satellite
Country: United StatesUnited States United States
Operator: National Aeronautics and Space AdministrationNASA NASA
COSPAR-ID : 1999-070B
Mission dates
Begin: December 20, 1999
Starting place: Vandenberg AFB
Launcher: Taurus 2110
Status: Lost connection on December 14, 2013
Orbit data
Rotation time : 99 min
Orbit inclination : 98.3 °
Apogee height :  683 km
Perigee height :  727 km

The Active Cavity Radiometer Irradiance Monitor Satellite ( ACRIMSat ) is a research satellite launched on December 20, 1999 by the US aerospace authority NASA , which investigated the energy radiation of the sun and its effect on the earth's climate .

ACRIMSat was part of the Earth Observing System (EOS), a multi-mission, long-term research program of NASA.

Orbit information

The satellite moves in a polar , sun-synchronous earth orbit (SSE). This type of earth orbit has the advantage that the satellite never enters the earth's shadow and can thus observe the sun around the clock.

mission

Computer animation from ACRIMSat

The sun, the center of our solar system , emits the energy that creates winds on earth , creates currents in the oceans , warms the land and is therefore responsible for global weather .

Scientists studying global climate change believe that only small fluctuations in the sun's energy radiation over a few decades, also known as Total Solar Irradiance (TSI), could play a role in climate change. By measuring this total amount of energy that reaches the earth from the sun and enters the earth's atmosphere , better models of the earth's climate system should be possible, which are an important part of the puzzle of global climate change.

ACRIMSat's task is to monitor the sun's energy radiation for five years and thus to continue collecting measurement data with the same instrument after two previous missions.

Fluctuations in energy radiation

The sun in H -alpha light

With the first version of the ACRIM instrument , ACRIM-I, on board the research satellite Solar Maximum Mission (SMM) in 1980, it could be clearly proven that the energy radiation of the sun is not constant and that the fluctuations are caused by magnetic activities in the sun. However, these fluctuations are so small (less than 0.00425 percent of the total energy of a year on time scales of individual days) that constant monitoring required powerful tools to obtain correct data.

There are theories that up to 25 percent of global warming in the 20th century can be attributed to fluctuations in the sun's energy output. Even fluctuations in the size range of 0.25 percent in a century could cause significant climate changes. For example, climate researchers are of the opinion that the Little Ice Age , which hit Europe and North America in the 17th century , can be linked to the minimum in solar activity that prevailed at the same time ( see Maunder minimum ).

The importance of this measurement data in climate studies

This long-term data on the energy radiated from the sun can be included in the creation of global climate models in order to increase their accuracy. In order to be able to develop climate models, measurement data from two different measurements are required:

  • The total amount of solar energy that reaches the earth; consisting of the visible light (ca. 85%), ultraviolet - (about 10%) and near infrared - wavelengths (about 5%)
  • The amount of energy that is reflected from the earth back into space and thus does not become part of the earth's energy system

The first measurement is carried out by the ACRIM-III instrument on board ACRIMSat, while other NASA satellites are responsible for the second measurement . The difference between the energy that reaches the earth and that which is reflected back into space results in the amount of energy that is responsible for the processes in the environment on earth. Combined with measurements of ocean currents , winds and surface temperatures , climate models can be created that can make statements about the future of the earth's climate.

The satellite

Structure of ACRIMSat

The satellite is a total of 115 kilograms heavy and was approved by the Orbital Sciences Corporation (OSC) in Dulles ( Virginia developed) and manufactured.

The Active Cavity Radiometer Irradiance Monitor

The analysis of the energy radiation is carried out by the Active Cavity Radiometer Irradiance Monitor (ACRIM), a powerful instrument that is used for the third time in the observation of our central star. It is developed for NASA and manufactured by the Jet Propulsion Laboratory (JPL), a division of the California Institute of Technology (Caltech). The instrument is able to measure electromagnetic waves with wavelengths between 200 nm and 2 µm. This includes visible light as well as ultraviolet and infrared radiation .

course

time event
September 1997 The ACRIMSat project begins. Funding in the amount of 17 million US dollars takes over the Earth Science Program Office of the Goddard Space Flight Center (GSFC) NASA in Greenbelt ( Maryland ). Dr. Richard C. Willson of Columbia University , while Roger Helizon of JPL is the project manager and responsible for the construction of the ACRIM instrument.
April 1999 The Orbital Sciences Corporation includes the works from at ACRIMSat.
December 20, 1999 ACRIMSat will be launched together with the KOMPSat-I (Korea Multi-Purpose Satellite) satellites of the Korea Aerospace Research Institute (KARI) and Celestis-IV at the Vandenberg Air Force Base in California and will be placed in orbit with the Taurus 2110 launcher . After the start there are initially problems with the control system, which is not able to align the satellite precisely with the sun, but this can be fixed by correcting the control software.
April 2000 ACRIMSat is only now sending scientific data as it has taken a long time to solve the tax problems.
June 2000 The OSC first subjects ACRIMSat to extensive tests and then hands over control to JPL in Pasadena (California), which begins the scientific use of the satellite and takes over its control.
January 2005 ACRIMSat is still in use, the mission is being extended.
December 14, 2013 The connection to ACRIMSat is lost and all communication attempts are unsuccessful. An old battery is assumed to be the cause.
5th April 2014 ACRIMSat is still in use. An impending collision with the European Sentinel-1 A satellite is avoided by its orbit maneuver.
August 8, 2014 Official end of the mission
Taurus 2110 missile

See also

literature

  • Richard C. Willson, Alexander V. Mordvinov: Secular total solar irradiance trend during solar cycles 21-23 . In: Geophysical Research Letters , Series 30, No. 5, 1199, 2003, doi: 10.1029 / 2002GL016038

Web links

Individual evidence

  1. ↑ a b ACRIMSAT - About the mission. NASA, August 8, 2014, accessed June 14, 2016 .
  2. ↑ ACRIMSAT (Active Cavity Radiometer Irradiance Monitor Satellite). ESA, accessed on April 11, 2014 (English): "The AcrimSat spacecraft and its payload are operating nominally in 2014."
  3. ↑ Elizabeth Howell: European Satellite Dodged Space Debris Hours After Reaching Orbit. Universe Today, April 10, 2014, accessed April 11, 2014 .