The SORCE Satellite
To continue to monitor the Sun and to cut down on the uncertainty of solar energy measurements, NASA launched the SORCE satellite on January 25, 2003. The satellite flies at an altitude of 640 km in a 40-degree-inclination orbit around the Earth. On board SORCE are four instruments that will greatly improve the accuracy of the measurements of solar energy. All instruments take readings of the Sun during each of the satellite’s 15 daily orbits. The information is transmitted to ground stations at NASA’s Wallops Flight Facility in Virginia and a station in Santiago, Chile.

The SORCE satellite carries four instruments to study the Sun. TIM, SIM, and SOLSTICE measure solar irradiance and the solar spectrum to help scientists understand the Sun’s role in climate change. The XPS measures high-energy radiation from the Sun. (Image courtesy Solar Radiation and Climate Experiment Project)

Three of the four SORCE instruments will be of direct use to Earth scientists. They are the Total Irradiance Monitor (TIM), the Spectral Irradiance Monitor (SIM), and the Solar Stellar Irradiance Comparison Experiment (SOLSTICE). TIM will accurately determine the TSI by recording the sum of the energy from nearly all the Sun’s wavelengths. SIM will measure upper portion of the ultraviolet spectrum (200–400 nm), the full visible range, and the near infrared up to 2000 nm. SOLSTICE will measure the full ultraviolet beginning at 100 nm, and includes the lower half of the ultraviolet region of SIM (200-300 nm). The 200–300 nm portion of ultraviolet measured by both SIM and SOLSTICE overlaps with UV-B (290–320 nm) which causes skin cancer, and is normally blocked from us by the stratosphere’s ozone layer. (See Ultraviolet Radiation: How it Affects Life on Earth) Its readings will be of primary importance to understanding the Sun’s impact on the stratosphere. A fourth instrument, known as the Extreme Ultraviolet Photometer System (XPS), will be of indirect use to Earth scientists. The instrument will measure very high-energy ultraviolet radiation and lower energy x-ray wavelengths. These readings should yield valuable information about the Sun’s corona, solar events that impact satellite communications, and the Sun’s effects on the very outermost layers of the Earth’s atmosphere.

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Solar Radiation and Climate Experiment (SORCE)
Introduction
Earth’s Energy Balance
Solar Variability
The Sun and Global Warming
Uncertainties in Solar Measurements

The SORCE Satellite
Total Irradiance Monitor (TIM)
Spectral Irradiance Monitor (SIM)
Solar Stellar Comparison Experiment (SOLSTICE)
Extreme Ultraviolet Photometer System (XPS)

Related Articles
SOLSTICE
Watching the Sun
ACRIMSAT
Sunspots and the Solar Max
Clouds and Radiation
Why isn’t Earth Hot as an Oven?

Related Datasets
Reflected Solar Radiation
Outgoing Heat Radiation