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Microsat 1



Microsat 1 was launched using a Pegasus booster rocket. The payload was delivered to orbit by vehicle released from a B-52. About an hour after take off from Edwards AFB, the 15-m long, 1.2-m-diameter 19,026-kg Pegasus was dropped from the aircraft and its engines ignited. A stage separation malfunction, however, cast the 7-satellite payload into a lower than anticipated orbit. Ground controllers could not make contact with the satellites and it appeared that they were lost. Some 9 hours after launch, telemetry was acquired as the Microsats passed over the main control station. Apparently, a new fourth stage guidance system compensated for the separation glitch and modified the trajectory. Subsequent passes verified that all 7 satellite were operating. Built by Defense Systems Inc. for the Defense Advanced Research Projects Agency (DARPA), the 12-sided Microsats measured 10 cm by 48 cm and weighed 22 kg each. They were designed to assess the use of low-earth orbit for global communications. Each satellite operated in UHF, using an analog transponder for FM radio relay of voice communications and a digital transponder to relay data, message, facsimile and modest video traffic. Although the 359 by 457-km orbit fell short of the planned 719 km, the inclination was on target, allowing mission objectives to be met.

Alternate Names

  • 21580
  • Microsat1

Facts in Brief

Launch Date: 1991-07-17
Launch Vehicle: Pegasus
Launch Site: Vandenberg AFB, United States
Mass: 22 kg

Funding Agency

  • Defense Advanced Research Projects Agency (United States)


  • Communications
  • Engineering

Additional Information

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

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