NASA’s Source Satellite Marks a Decade in the Sun
NASA’s Solar Radiation and Climate Experiment (SORCE) satellite has been providing data on the sun’s irradiance for 10 years. SORCE measures electromagnetic radiation produced by the sun and the power per unit area of that energy on the Earth’s surface.
SORCE has set a new standard of accuracy, precision, and wavelength range for the sun’s irradiance,” said Robert Cahalan, SORCE Project Scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md. “[It’s] a kind of climate gold standard’ for the radiative forcing of Earth over the decade of the 2000s, beginning with the dramatic Halloween flares of October-November 2003, through the historically low 2008-2009 minimum of Solar Cycle 23, into the rise of Solar Cycle 24, providing a climate record likely to grow in value for sun and Earth studies over many decades to come.”
SORCE was launched on January 25, 2003 and began normal operations on March 6, 2003. The mission of SORCE was to collect a continuous record of the sun’s Total Solar Irradiance (TSI) and Spectral Solar Irradiance (SSI). The SORCE spacecraft carries four observational instruments: Total Irradiance Monitor (TIM), Solar Stellar Irradiance Comparison Experiment (SOLSTICE), Solar Irradiance Monitor (SIM), and soft X-ray Ultraviolet Photometer System (XPS).
Top 10 Scientific Achievements
- Established a new level of TSI that is 4.6 W/m2 (0.34%) lower than prior space-based observations.
- Acquired the first continuous measurements of SSI in the 115- to 2400-nm spectral range.
- Defined a reference spectrum of the Sun’s spectral irradiance from 0.1 to 2400 nm during very quiet solar conditions.
- Provided total and spectral irradiance inputs to the climate and atmospheric communities, and used in a wide variety of simulations and models.
- Implemented next-generation instrumentation of spaceflight radiometers for solar irradiance monitoring with the highest accuracy and precision yet achieved.
- Seamlessly extended the National Oceanic and Atmospheric Administration’s (NOAA’s) Mg II index of chromospheric activity.
- Acquired the first solar flare measurements in TSI, and accompanying spectral variations.
- Advanced and validated models of the Sun’s total and spectral irradiance variability.
- Observed two Venus transits and two Mercury transits of the Sun, demonstrating exo-solar planet detection capabilities and limitations.
- Validated the white dwarf flux scale for absolute calibration of instruments for UV astronomy and made the first absolute measurement of disk integrated lunar UV reflectance.