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UFO 8 (UHF Follow On 8) was a US Navy satellite launched to replace the FLTSATCOM and Leasat spacecraft currently supporting the Navy's global communications network, serving ships at sea and a variety of other US military fixed and mobile terminals. It was compatible with ground- and sea-based terminals already in service.

The UHF F/O satellites offered increased communications channel capacity over the same frequency spectrum used by previous systems. Each spacecraft had 11 solid-state UHF amplifiers and 39 UHF channels with a total of 555 kHz bandwidth. The UHF payload compressed 21 narrow band channels at 5 kHz each and 17 relay channels at 25 kHz. In comparison, FLTSATCOM offered 22 channels. The F-1 through F-7 spacecraft included an SHF (super high frequency) subsystem, which provided command and ranging capabilities when the satellite was on station as well as the secure uplink for Fleet Broadcast service, which was downlinked at UHF. On the F-8 through F-10 missions, the SHF payload was replaced by the GBS (Global Broadcast Service) package that revolutionized communications for the full range of the Defense Department's high-capacity requirements, from intelligence dissemination to quality-of-life programming.

Each satellite measured more than 60 feet long from the tip of one three-panel solar array wing to the tip of the other. These arrays generated a combined 2500 watts of electrical power on the first three satellites, 2800 watts for F-4 through F-7, and 3800 watts for F-8 through F-10 with GBS. The arrays were folded against the spacecraft bus for launch, forming a cube roughly 11 feet per side.

Alternate Names

  • 25258
  • UHF Follow On 8
  • USA 138
  • UHF F8
  • UFO8

Facts in Brief

Launch Date: 1998-03-16
Launch Vehicle: Atlas 2AS
Launch Site: Cape Canaveral, United States
Mass: 1000 kg
Nominal Power: 1200 W

Funding Agency

  • Department of Defense-Department of the Navy (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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