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SORCE (Solar Radiation and Climate Experiment) will make precise and accurate measurements of the Total Solar Irradiance (TSI). These measurements will be connected with previous TSI measurements to continue a long-term record of solar influences on the Earth. SORCE will measure TSI with an absolute accuracy of 0.01% and with a longterm relative accuracy of 0.001% per year. SORCE will make precise measurements of the visible and near infrared Spectral Solar Irradiance (SSI) suitable for future climate studies. SORCE will obtain daily measurements of the SSI from 300 to 2000 nm, with a spectral resolution of approximately 30 nm, an absolute accuracy of 0.03%, and a precision and relative accuracy of better than 0.01% per year. SORCE will make daily measurements of the ultraviolet solar irradiance from 120 to 300 nm with a spectral resolution of 1 nm. It will achieve this measurement with an absolute accuracy of better than 5% and with a longterm relative accuracy of 0.5% per year. SORCE observations will improve our understanding of how and why solar variability occurs and how it affects our atmosphere and climate. This knowledge can be used to estimate past and future solar behavior and climate response.

The SORCE satellite consists of a spacecraft bus and four instruments funded by NASA. The four instruments on-board were designed and built by LASP at the University of Colorado in Boulder. They are:

  • the Total Irradiance Monitor (TIM),
  • the Spectral Irradiance Monitor (SIM),
  • two identical Solar Stellar Irradiance Comparison Experiments (SOLSTICE), and
  • the XUV Photometer System (XPS).

TIM, SIM, and SOLSTICE will measure total solar irradiance and the solar spectrum to help scientists understand the Sun's role in climate change. The XPS will measure high-energy radiation from the Sun.

The spacecraft carrying the instruments was developed by the Orbital Sciences Corporation in Dulles, Virginia, under contract to LASP. This spacecraft is three-axes stabilized with a control system to point the instruments at the Sun and the calibration stars. The stowed spacecraft is 100 centimeters wide × 160.3 centimeters high. With solar arrays deployed, SORCE is 339.3 centimeters wide × 160.3 centimeters high. The spacecraft, at launch, weighs 287 kilograms (?). The spacecraft is powered by 348 Watts of electric power from its solar array.

Nation: USA
Type / Application: Earth science
Operator: NASA
Contractors: Orbital Sciences Corporation (OSC)
Equipment: TIM, SIM, 2 SOLSTICE, XPS
Configuration: LEOStar-2
Propulsion: ?
Power: 6 deployable fixed solar arrays, batteries
Mass: 315 kg
Orbit: 645 km, 40
Satellite COSPAR Date LS Launch Vehicle Remarks
SORCE 2003-004A 25.01.2003 CC, L-1011, RW13/31 Pegasus-XL


  • Orbital Sciences Corp.: SORCE