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The Solar Radiation and Climate Experiment (SORCE) was a 2003–2020
NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...
-sponsored satellite mission that measured incoming
X-ray An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays. Roughly, X-rays have a wavelength ran ...
,
ultraviolet Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...
, visible,
near-infrared Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those of ...
, and total solar radiation. These measurements specifically addressed long-term
climate change Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...
, natural variability, atmospheric ozone, and UV-B radiation, enhancing climate prediction. These measurements are critical to studies of the
Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...
, its effect on the
Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...
's system, and its influence on humankind. SORCE was launched on 25 January 2003 on a Pegasus XL
launch vehicle A launch vehicle is typically a rocket-powered vehicle designed to carry a payload (a crewed spacecraft or satellites) from Earth's surface or lower atmosphere to outer space. The most common form is the ballistic missile-shaped multistage ...
to provide
NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...
's Earth Science Enterprise (ESE) with precise measurements of solar radiation. SORCE measured the
Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...
's output using
radiometers A radiometer or roentgenometer is a device for measuring the radiant flux (power) of electromagnetic radiation. Generally, a radiometer is an infrared radiation detector or an ultraviolet detector. Microwave radiometers operate in the microwave w ...
,
spectrometers A spectrometer () is a scientific instrument used to separate and measure Spectrum, spectral components of a physical phenomenon. Spectrometer is a broad term often used to describe instruments that measure a continuous variable of a phenomeno ...
, photodiodes, detectors, and bolometers mounted on a
satellite A satellite or an artificial satellite is an object, typically a spacecraft, placed into orbit around a celestial body. They have a variety of uses, including communication relay, weather forecasting, navigation ( GPS), broadcasting, scient ...
observatory orbiting the Earth. Spectral measurements identify the irradiance of the Sun by characterizing the Sun's energy and emissions in the form of color that can then be translated into quantities and elements of matter. Data obtained by SORCE can be used to model the Sun's output and to explain and predict the effect of the Sun's radiation on the Earth's atmosphere and climate. Flying in a orbit at a 40.0°
inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Eart ...
, SORCE was operated by the
Laboratory for Atmospheric and Space Physics The Laboratory for Atmospheric and Space Physics (LASP) is a research organization at the University of Colorado Boulder. LASP is a research institute with over one hundred research scientists ranging in fields from solar influences, to Earth ...
(LASP) at the
University of Colorado Boulder The University of Colorado Boulder (CU Boulder, CU, or Colorado) is a public research university in Boulder, Colorado, United States. Founded in 1876, five months before Colorado became a state, it is the flagship university of the University o ...
,
Colorado Colorado is a U.S. state, state in the Western United States. It is one of the Mountain states, sharing the Four Corners region with Arizona, New Mexico, and Utah. It is also bordered by Wyoming to the north, Nebraska to the northeast, Kansas ...
. It continued the precise measurements of
total solar irradiance Solar irradiance is the power per unit area ( surface power density) received from the Sun in the form of electromagnetic radiation in the wavelength range of the measuring instrument. Solar irradiance is measured in watts per square metre ...
that had begun with the ERB instrument in 1979 and had been later extended with the ACRIM series of measurements (1999+). SORCE provided measurements of the solar spectral irradiance from 1 to 2000 nm, accounting for 95% of the spectral contribution to the total solar irradiance.


Objectives

The science objectives of the SORCE mission were: * To make accurate measurements with high precision of total solar irradiance, connect them to previous TSI measurements, and continue this long-term climate record. Provide TSI with an accuracy of 0.01% (100 parts per million) based on SI units and with long-term repeatability of 0.001%/yr. * To make daily measurements of the solar ultraviolet irradiance from 120 to 300 nm, with a spectral resolution of 1 nm. Achieve this spectral irradiance measurement with an accuracy of better than 5%, and with long-term repeatability of 0.5%/yr. Use the solar/stellar comparison technique to relate the solar irradiance to the ensemble average flux from a number of bright, early-type stars (same stars used by the
Upper Atmosphere Research Satellite The Upper Atmosphere Research Satellite (UARS) was a NASA-operated orbital observatory whose mission was to study the Earth's atmosphere, particularly the protective ozone layer. The satellite was deployed from Space Shuttle Discovery, Space Shu ...
(UARS) SOLSTICE program). * To make the first measurements of the visible and near-infrared solar irradiance with sufficient precision for future climate studies. Obtain daily measurements of solar spectral irradiance between 0.3 and 2 μm with a spectral resolution of at least 1/30, an accuracy of 0.03%, and long-term repeatability of better than 0.01%/yr. * To improve the understanding of how and why solar irradiance varies, estimate past and future solar behavior, and investigate climate responses.


Experiments

SORCE carried four instruments, including the Total Irradiance Monitor (TIM), Solar Stellar Irradiance Comparison Experiment (SOLSTICE), Spectral Irradiance Monitor (SIM), and the XUV Photometer System (XPS):


Total Irradiation Monitor (TIM)

TIM (Total Irradiation Monitor) was a 7.9 kg, 14 watts instrument that covered all visual and infrared wavelengths at an irradiance accuracy of one part in 10000. It used differential, heat-sensitive resistors as detectors.


Spectral Irradiance Monitor (SIM)

SIM (Spectral Irradiance Monitor) was a 22 kg, 25 watts rotating Fery prism spectrometer with a bolometer output that covered the 200-2400 nm band at a resolution of a few nm, and at an irradiance accuracy of three parts in ten thousand.


Solar Stellar Irradiance Comparison Experiment (SOLSTICE)

SOLSTICE (SOlar STellar Irradiance Comparison Experiment) A and B are 36 kg, 33 watts, UV grating spectrometers with photomultiplier detectors that covered the 115-320 nm band at a resolution of 0.1 nm, and at an irradiance accuracy of about 4%. It used an ensemble of bright stars (selected for their stable luminosities) as calibrators for the instrument variability.


Extreme Ultraviolet Photometer System (XPS)

XPS (XUV Photometer System) was a 3.6 kg, 9 watts photometer which invoked filters to monitor the
X-ray An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays. Roughly, X-rays have a wavelength ran ...
and UV band at 1-34 nm, at a resolution of about seven nm, and at an irradiance accuracy of about 15%.


End of mission

NASA decommissioned SORCE on 25 February 2020, after 17 years of operation (over three times the original design life of five years). The spacecraft had struggled with battery degradation problems since 2011, which prevented SORCE from conducting measurements full-time. Ground teams switched to daytime-only observations, effectively allowing SORCE to operate with no functioning battery through its
solar panels A solar panel is a device that converts sunlight into electricity by using photovoltaic (PV) cells. PV cells are made of materials that produce excited electrons when exposed to light. These electrons flow through a circuit and produce direct ...
. NASA planned to keep operating SORCE until a replacement could be developed and launched. The Glory satellite, which would have continued SORCE's observations, was lost in a launch failure in 2011. A stopgap solar irradiance instrument, the Total Solar Irradiance Calibration Transfer Experiment (TCTE), was launched in November 2013 on the U.S. Air Force's STPSat-3, but a full replacement for SORCE did not launch until December 2017, when the Total and Spectral solar Irradiance Sensor (TSIS-1 and TSIS-2) was delivered to the
International Space Station The International Space Station (ISS) is a large space station that was Assembly of the International Space Station, assembled and is maintained in low Earth orbit by a collaboration of five space agencies and their contractors: NASA (United ...
(ISS). Left to drift in orbit, SORCE is projected to re-enter the atmosphere in 2032, with most of the spacecraft expected to burn up during re-entry.


See also

*
Upper Atmosphere Research Satellite The Upper Atmosphere Research Satellite (UARS) was a NASA-operated orbital observatory whose mission was to study the Earth's atmosphere, particularly the protective ozone layer. The satellite was deployed from Space Shuttle Discovery, Space Shu ...


References


External links

* http://lasp.colorado.edu/sorce/ {{Sun spacecraft Satellites orbiting Earth Spacecraft launched in 2003 Spacecraft decommissioned in 2020 Solar observatories Spacecraft launched by Pegasus rockets NASA satellites