OSO 3, third Orbiting Solar Observatory (known as OSO C before launch) was launched on March 8, 1967, into a nearly circular orbit of mean altitude 550 km, inclined at 33° to the equatorial plane. Its on-board tape recorder failed on June 28, 1968, allowing only the acquisition of sparse real-time data during station passes thereafter; the last data were received on November 10, 1969. OSO 3 reentered the Earth's atmosphere and burned up on April 4, 1982.

Like all the American OSO-series

Orbiting Solar Observatory

The Orbiting Solar Observatory Program was the name of a series of nine American science satellites primarily intended to study the Sun, though they also included important non-solar experiments. Eight were launched successfully by NASA between 1962 and 1975 using Delta rockets...

 satellites, it had two major segments: one, the "Sail", was stabilized to face the Sun, and carried both solar panels and Sun-pointing experiments for solar physics. The other, "Wheel" section, rotated to provide overall gyroscopic stability and also carried sky scanning instruments that swept the sky as the wheel turned, approximately every 2 sec.

Instrumentation

Experiments on board OSO 3

Name	Target	Principal Investigator
High Energy Gamma Ray (> 50 MeV)	anti-solar	Kraushaar, W. L., Massachusetts Institute of Technology Massachusetts Institute of Technology The Massachusetts Institute of Technology is a private research university located in Cambridge, Massachusetts. MIT has five schools and one college, containing a total of 32 academic departments, with a strong emphasis on scientific and technological education and research.Founded in 1861 in...
Cosmic Ray Spectrum Detector and Gamma Ray Analyzer	Sun Sun The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields... , all-sky	Kaplon, Morton F, University of Rochester University of Rochester The University of Rochester is a private, nonsectarian, research university in Rochester, New York, United States. The university grants undergraduate and graduate degrees, including doctoral and professional degrees. The university has six schools and various interdisciplinary programs.The...
Directional Radiometer Experiment	Earth Earth Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...	Neel, Carr B Jr, NASA Ames Research Center NASA Ames Research Center The Ames Research Center , is one of the United States of America's National Aeronautics and Space Administration 10 major field centers.The centre is located in Moffett Field in California's Silicon Valley, near the high-tech companies, entrepreneurial ventures, universities, and other...
Earth Albedo (0.32- to 0.78-µm)	Earth Earth Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...	Neel, Carr B Jr, NASA Ames Research Center NASA Ames Research Center The Ames Research Center , is one of the United States of America's National Aeronautics and Space Administration 10 major field centers.The centre is located in Moffett Field in California's Silicon Valley, near the high-tech companies, entrepreneurial ventures, universities, and other...
Solar EUV Spectrometer 0.1 to 40.0 nm	Sun Sun The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...	Neupert, Werner M, NASA Goddard Space Flight Center
0.8- to 1.2-nm Solar X-Ray Ion Chamber	Sun Sun The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...	Teske, Richard G, University of Michigan University of Michigan The University of Michigan is a public research university located in Ann Arbor, Michigan in the United States. It is the state's oldest university and the flagship campus of the University of Michigan...
Solar and Celestial Gamma-Ray Telescope (7.7 to 200 keV)	Sun Sun The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields... , all-sky	Peterson, Laurence E, University of California, San Diego University of California, San Diego The University of California, San Diego, commonly known as UCSD or UC San Diego, is a public research university located in the La Jolla neighborhood of San Diego, California, United States...
Thermal Radiation Emissivity	near-Earth Earth Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...  space environment	Neel, Carr B Jr, NASA Ames Research Center NASA Ames Research Center The Ames Research Center , is one of the United States of America's National Aeronautics and Space Administration 10 major field centers.The centre is located in Moffett Field in California's Silicon Valley, near the high-tech companies, entrepreneurial ventures, universities, and other...
Extreme Ultraviolet Spectrometer	Sun Sun The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...	Hinteregger, Hans E, Phillips Laboratory Phillips Laboratory Phillips Laboratory was a research and development organization operated by the United States Air Force Materiel Command. In 1997, the Laboratory was merged into the Air Force Research Laboratory as the Space Vehicles and Directed Energy Directorates. It was located at Kirtland Air Force Base in...

The Sail carried a hard X-ray experiment from UCSD, with a single thin NaI(Tl) scintillation crystal plus phototube enclosed in a howitzer-shaped CsI(Tl) anti-coincidence shield. The energy resolution was 45% at 30 keV. The instrument operated from 7.7 to 210 keV with 6 channels. The Principal Investigator (PI) was Prof. Laurence E. Peterson

Laurence E. Peterson

Laurence E. Peterson is Emeritus Professor of Physics and Director of the Center for Astrophysics and Space Sciences at the University of California, San Diego, California.He received his Ph.D in 1960 from the University of Minnesota....

 of UCSD. Also in the wheel was a cosmic gamma-ray (>50 MeV

MEV

MeV and meV are multiples and submultiples of the electron volt unit referring to 1,000,000 eV and 0.001 eV, respectively.Mev or MEV may refer to:In entertainment:* Musica Elettronica Viva, an Italian musical group...

) sky survey instrument contributed by MIT, with PI Prof. William L. Kraushaar].

Scientific results

OSO-3 obtained extensive observations of solar flares, the cosmic diffuse X-ray background, and the observation of a single flare episode from Scorpius X-1

Scorpius X-1

Scorpius X-1 is an X-ray source located roughly 9000 light years away in the constellation Scorpius. Scorpius X-1 was the first extrasolar X-ray source discovered, and, aside from the Sun, it is the strongest source of X-rays in the sky...

, the first observation of an extrasolar X-ray source by an observatory satellite.
The MIT gamma-ray instrument obtained the first identification of high-energy cosmic gamma rays emanating from both galactic and extra-galactic sources.

External links

The content of this article was adapted and expanded from NASA's HEASARC: Observatories OSO 3 http://heasarc.nasa.gov/docs/heasarc/missions/oso3.html and NASA's National Space Science Data Center: OSO 3 http://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1967-020A (Public Domain)