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Milstar-2 F1, also known as USA 143, was to be an American geosynchronous military communications spacecraft. The Titan vehicle operated correctly, but a software error in the Centuar stage resulted in all three planned burns being made at the wrong time, during the first orbit instead of over a six hour period. The three burns planned to place Milstar in a 170 x 190 km parking orbit, a geostationary transfer orbit, and finally geosynchronous orbit. Instead, several hours before the scheduled third burn, Milstar separated into a useless 740 x 5000 km orbit. It was the first upgraded Milstar with an extra Medium Data Rate payload with a higher throughput. The payload included EHF (44 GHz), SHF (20 GHz), and UHF communications transponders and satellite-to-satellite crosslinks, with narrow beams to avoid jamming.

Alternate Names

  • USA 143
  • 25724
  • MILSTAR 2 F1

Facts in Brief

Launch Date: 1999-04-30
Launch Vehicle: Titan 4B
Launch Site: Cape Canaveral, United States

Funding Agency

  • Department of Defense-Department of the Army (United States)


  • Communications
  • Surveillance and Other Military

Additional Information

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

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