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OV1-20 was one of nine spacecraft simultaneously placed into orbit from a single launch vehicle. The satellite carried two experiments -- an energetic (above 70 MeV) proton analyzer and a particle energy and thermal flux detector for measuring the electron density and temperature in the upper ionosphere. In addition, the satellite served as the launching platform for the OAR 901 spacecraft (Cannon Ball 2). OV1-20 was cylindrical in shape, measuring 2.13 m in length and .6 m in diameter. A plasma probe was mounted on an approximately 1.5-m-long boom that protruded from the center of the vehicle. The spacecraft electrical systems included a 136.740-mHz telemetry transmitter, a signal conditioner, a pcm multiplexer encoder, an s-band transmitter, and a c-bane transponder. Electrical power for the spacecraft and the experiments was provided by two silver-zinc batteries. To conserve power, the experiment operating sequence was controlled by an onboard timer. Only real-time data were transmitted, which limited the data acquisition to south-to-north passes between 65 deg s and 65 deg n latitude. The spacecraft performed normally after launch. All data acquisition activities were terminated on August 16, 1971, when the spacecraft's battery power pack became depleted. OV1-20 reenterred the earth's atmosphere on August 28, 1971.

Alternate Names

  • 05394
  • SESP 70-2A

Facts in Brief

Launch Date: 1971-08-07
Launch Vehicle: Atlas
Launch Site: Vandenberg AFB, United States
Mass: 70 kg

Funding Agency

  • Department of Defense-Department of the Air Force (United States)


  • Space Physics

Additional Information

Questions and comments about this spacecraft can be directed to: Coordinated Request and User Support Office



NameRoleOriginal AffiliationE-mail
Capt G. PetersonProject ManagerUS Air Force Space Division
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