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MIDAS 3 (MIssile Defense Alarm System) was a satellite placed in a circular earth orbit to measure IR background and define IR sources. This was an overall test of a system for detection of missile launchings with satellite-borne IR sensors. The payload was the same as for MIDAS 2, except that an Agena B replaced the Agena A as the upper stage. The satellite carried experiments on cosmic radiation, atmospheric density, radiometric measurement, and micrometeorite detection, and had a plasma probe. The spacecraft weighed 3500 lb (including the second-stage casing), was chemical-battery-powered, and was launched from the pacific missile range. Useful IR radiation data were received for the lifetime of the battery pack.

Alternate Names

  • 00163
  • Missile Defense Alarm System 3
  • 1961 Sigma 1
  • MIDAS3

Facts in Brief

Launch Date: 1961-07-12
Launch Vehicle: Atlas
Launch Site: Point Arguello, United States
Mass: 1600 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



NameRoleOriginal AffiliationE-mail
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