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Discoverer 25



Discoverer 25 was launched by the U.S. Air Force Ballistic Missile Division (AFBMD) as part of a program to evaluate spacecraft design changes and to provide a stable platform for developing and testing various space experiments. The spacecraft carried instrumentation on board to measure cosmic radiation, atmospheric pressure, and micrometeoroid impacts. The spacecraft also contained samples of both rare earth and common metals in order to study the effects of cosmic radiation on various materials. The spacecraft consisted of a cylindrical rocket body (approximately 6 m long and 1.5 m in diameter) equipped with a liquid propellant rocket engine, propellant tanks, and nose cone which housed the telemetry, the guidance and control systems, and the experiment package. Once in orbit, the satellite could be reoriented in a nose-down position facing earthward. The nose cone could be separated from the spacecraft while in orbit. The cone was equipped with retrorockets to slow it down and allow for reentry. The spacecraft performed normally after launch. The nose cone separated on orbit number 33 (June 18, 1961) and was successfully recovered from the ocean that same day. The satellite itself was burned up during reentry on July 12, 1961.

Alternate Names

  • KH-2 9017
  • 00108
  • 1961 Xi 1
  • Discoverer25

Facts in Brief

Launch Date: 1961-06-16
Launch Vehicle: Thor
Launch Site: Vandenberg AFB, United States
Mass: 1150 kg

Funding Agency

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


  • Surveillance and Other Military
  • Space Physics
  • Astronomy

Additional Information

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



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