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The objectives of the OSO satellite series were to perform solar physics experiments above the atmosphere during a complete solar cycle and to map the celestial sphere for direction and intensity of UV light, X-rays, and gamma radiation. The OSO 1 was the first satellite to have pointed instruments and onboard tape recorders for data storage.

The OSO 1 platform was 94 cm high and primarily constructed of aluminum. It consisted of a sail section, which pointed experiments continuously toward the sun, supplying power to the experiments from p-n solar cells and rechargeable NiCd batteries; and a nonagonal wheel section 112 cm across, which spun at about 30 rpm about an axis perpendicular to the pointing direction of the sail, providing spin-stailization and carrying experiments.

The sail section was fan-shaped and stabilized to point at the Sun with an accuracy of one minute of arc in elevation and azimuth. It carried three solar X-ray experiments, a gamma-ray experiment, and a dust particle experiment. Fine elevation and azimuth positioning of the instruments was provided by electrical servo motors.

The wheel section had nine wedge-shaped compartments, five for experiments and four for various spaccraft systems. Three fiberglass balls extending on arms from three of the sides. The balls contained pressurized nitrogen for the gyroscopic control system, giving a total diameter of the spacecraft of 234 cm.

Attitude adjustment was performed by gas jets and the gyros. Attitude knowledge was provided by a Sun sensor. Data were simultaneously recorded on tape and transmitted by FM telemetry at 136.744 MHz to the MiniTrack system. A command system provided for 10 ground-based commands. Passive thermal control was used.

Following launch on 7 March 1962, the spacecraft performed normally for the first 1038 orbits until the second onboard tape recorder failed May 15, 1962. At this point, data could only be transmitted in real-time during station passes. On May 22 there was a malfunction in the spin control system. The spacecraft provided real-time data until May 1964, when the power cells failed. In all, OSO-1's thirteen experiments provided almost 1000 hours of useful data on solar phenomena, including measurements on 75 solar flares and subflares. For more information, see A. W. L. Ball, Spaceflight, v. 12, p. 244, 1970.

It is believed that the solar cells were damaged by the Starfish Prime high-altitude nuclear test, and that this led to the eventual failure of the spacecraft power cells in May 1964. It fell silent on 6 August 1966.

Starfish Prime

Starfish Prime was an American high-altitude nuclear test that took place on 9 July 1962. Launch took place from Johnston atoll in the Pacific Ocean (about 1330 km southwest of Honolulu) at 8:46:28 UT on 9 July 1962 (10:46:28 pm, 8 July local time) on a Thor rocket carrying a W49 thermonuclear warhead. Detonation of the warhead occurred at 09:00:09 UT on 9 July (11:00:09 pm local time, 8 July) at an altitude of 400 km. Total yield was 1.4 megatons. The explosion, occurring at a geomagnetic latitude 10.5 degrees, generated an electromagnetic pulse and large quantities of charged particles. These had the effect of damaging many operating satellites, both at the time of the blast and later, as the energetic particles remained trapped in the Earth's magnetic field, forming an artificial radiation belt that persisted for many weeks after the explosion. These damaged satellites include TRAAC, Transit-4B, Ariel 1, Cosmos 5, Telstar 1, Explorers 14 and 15, and possibly Injun 1, OSO-1, Alouette 1, and ANNA-1B.

Alternate Names

  • 00255
  • 1962 Zeta 1
  • OSO-A
  • OSO1
  • S 16

Facts in Brief

Launch Date: 1962-03-07
Launch Vehicle: Thor-Delta
Launch Site: Cape Canaveral, United States
Mass: 207.7 kg
Nominal Power: 16 W

Funding Agency

  • NASA-Office of Space Science Applications (United States)


  • Planetary Science
  • Space Physics
  • Solar Physics
  • Astronomy

Additional Information

Questions and comments about this spacecraft can be directed to: Dr. David R. Williams



NameRoleOriginal AffiliationE-mail
Mr. John C. LindsayProject ManagerNASA Goddard Space Flight Center
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