Orbiting Solar Observatory


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Orbiting Solar Observatory

(OSO), series of eight orbiting observatories (see observatory, orbitingobservatory, orbiting,
research satellite designed to study solar radiation, electromagnetic radiation from distant stars, the earth's atmosphere, or the like. Because the atmosphere and other aspects of the earth's environment interfere with astronomical observations from the
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) launched between 1962 and 1971 by the National Aeronautics and Space Administration (NASA) to study the sun in the ultraviolet and X-ray wavelengths filtered out by the earth's atmosphere. The third to be launched, OSO-C, failed to achieve orbit. The other seven studied solar ultraviolet radiation and cosmic rays, measured radiation levels in the Van Allen radiation beltsVan Allen radiation belts,
belts of radiation outside the earth's atmosphere, extending from c.400 to c.40,000 mi (c.650–c.65,000 km) above the earth. The existence of two belts, sometimes considered as a single belt of varying intensity, was confirmed from information
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, detected neutrons, and investigated X-ray sources in the Milky Way and beyond. Through continuous monitoring of the sun over a 15-year period, the OSO program enhanced the understanding of the solar atmosphere and of the 11-year sunspot cycle. Among the significant achievements of the program were the first visible light and extreme ultraviolet photographs of the corona, the first full-disk photograph of the solar corona, and the first X-ray observations of a solar flare in the initial stage of eruption. See also ultraviolet astronomyultraviolet astronomy,
study of celestial objects by means of the ultraviolet radiation they emit, in the wavelength range from about 90 to about 350 nanometers. Ultraviolet (UV) line spectrum measurements are used to discern the chemical composition, densities, and temperatures
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Orbiting Solar Observatory

(OSO) Any of a series of US satellites launched between 1962 (OSO–1) and 1975 (OSO–8) and designed to study the Sun and solar phenomena, especially solar flares, from Earth orbit. The quality and range of the observations improved as the series progressed, with high spectral and spatial resolution in ultraviolet and X-ray spectral regions in later craft. Instruments have included a coronagraph, spectroheliograph, ultraviolet and X-ray spectrographs, photometers, gamma-ray detectors, and particle-flux sensors.