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Orbiting Solar Observatory (OSO)





OSO-3
OSO-3 undergoing spin-balance tests before launch
A series of stabilized orbiting platforms developed by the Goddard Space Flight Center for observing the Sun and extrasolar sources at ultraviolet, X-ray, and gamma-ray wavelengths. OSO-1 was the first satellite to carry onboard tape recorders for data storage and instruments that could be accurately pointed.

The two-section observatory was stabilized because the lower section, the "wheel," spun as a gyroscope at a near constant 30 rpm. The upper fan-shaped section, the "sail," was joined to the wheel by a connecting shaft and remained pointed at the Sun during the OSO daytime. Experiments in the wheel scanned the Sun every two seconds and those in the sail pointed continuously at the Sun.

Other results of the OSO series included the first full-disc photograph of the solar corona, the first X-ray observations from a spacecraft of a beginning solar flare and of solar streamers – structures in the corona – and the first observations of the corona in white light and extreme ultraviolet.


spacecraft launch date launch vehicle launch site orbit mass (kg)
OSO-1 Mar. 7, 1962 Delta Cape Canaveral 522 × 553 km × 32.8° 208
OSO-2 Feb. 3, 1965 Delta C Cape Canaveral 294 × 306 km × 32.8° 247
OSO-C Aug. 25, 1965 Delta C Cape Canaveral launch failure 280
OSO-3 Mar. 8, 1967 Delta C Cape Canaveral 546 × 570 km × 32.8° 281
OSO-4 Oct. 15, 1967 Delta C Cape Canaveral 552 × 555 km × 32.9° 272
OSO-5 Jan. 22, 1969 Delta C Cape Canaveral 538 × 559 km × 33.0° 291
OSO-6 Aug. 9, 1969 Delta N Cape Canaveral 489 × 554 km × 32.9° 290
OSO-7 Sep. 29, 1971 Delta N Cape Canaveral 326 × 572 km × 33.1° 635
OSO-8 Jun. 21, 1975 Delta 1914 Cape Canaveral 539 × 553 km × 32.9° 1,066


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   • SATELLITES AND SPACE PROBES