 Solar Radiation and Climate Experiment satellite | |
| Names | SORCE |
|---|---|
| Mission type | Astrophysics |
| Operator | NASA,LASP atUniversity of Colorado Boulder |
| COSPAR ID | 2003-004A |
| SATCATno. | 27651 |
| Website | https://lasp.colorado.edu/sorce/ |
| Mission duration | 5 years (planned) 22 years, 5 months and 6 days (in orbit) |
| Spacecraft properties | |
| Spacecraft type | Solar Radiation and Climate Experiment |
| Launch mass | 315 kg (694 lb) |
| Dry mass | 290 kg (640 lb) |
| Start of mission | |
| Launch date | 25 January 2003, 20:13:35UTC |
| Rocket | Pegasus XL |
| Launch site | Cape Canaveral (CCAFS), Lockheed L-1011 TriStar |
| Contractor | Orbital Sciences Corporation |
| End of mission | |
| Disposal | Decay in 2032 (planned) |
| Deactivated | 25 February 2020 |
| Orbital parameters | |
| Reference system | Geocentric orbit[1] |
| Regime | Geosynchronous orbit |
| Altitude | 645 km (401 mi) |
| Inclination | 40.00° |
| Period | 97.19 minutes |
| Instruments | |
| TIM - Total Irradiance Monitor SOLSTICE - Solar Stellar Irradiance Comparison Experiment SIM - Spectral Irradiance Monitor XPS =XUV Photometer System | |
TheSolar Radiation and Climate Experiment (SORCE) was a 2003–2020NASA-sponsored satellite mission that measured incomingX-ray,ultraviolet,visible,near-infrared, andtotal solar radiation.[2] These measurements specifically addressed long-termclimate change, natural variability,atmospheric ozone, andUV-B radiation, enhancing climate prediction. These measurements are critical to studies of theSun, its effect on theEarth's system, and its influence on humankind. SORCE was launched on 25 January 2003 on aPegasus XLlaunch vehicle to provideNASA'sEarth Science Enterprise (ESE) with precise measurements of solar radiation.
SORCE measured theSun's output usingradiometers,spectrometers,photodiodes, detectors, andbolometers mounted on asatellite observatory orbiting the Earth. Spectral measurements identify theirradiance 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 645 km (401 mi) orbit at a 40.0°inclination, SORCE was operated by theLaboratory for Atmospheric and Space Physics (LASP) at theUniversity of Colorado Boulder,Colorado. It continued the precise measurements oftotal solar irradiance that had begun with theERB instrument in 1979 and had been later extended with theACRIM 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.
The science objectives of the SORCE mission were:[3]
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):
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.[4]
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.[5]
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.[6]
XPS (XUV Photometer System) was a 3.6 kg, 9 watts photometer which invoked filters to monitor theX-ray andUV band at 1-34 nm, at a resolution of about seven nm, and at an irradiance accuracy of about 15%.[7]
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 itssolar panels.[8]
NASA planned to keep operating SORCE until a replacement could be developed and launched. TheGlory 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'sSTPSat-3,[9] but a full replacement for SORCE did not launch until December 2017, when theTotal and Spectral solar Irradiance Sensor (TSIS-1 and TSIS-2) was delivered to theInternational Space Station (ISS).[8]
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.[8]
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