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UFO 11 (UHF-FO Block 4)

UFO 11 (Block 4) [Boeing BSS]

The U.S. Navy began replacing and upgrading its ultra-high frequency (UHF) satellite communications network during the 1990s with a constellation of customized satellites built by Hughes Space and Communications Company, which is now Boeing Satellite Systems, Inc. Known as the UFO (Ultra High Frequency Follow On) series, these HS-601 model satellites support the Navy's global communications network, serving ships at sea and a variety of other U.S. military fixed and mobile terminals. They are compatible with ground- and sea-based terminals already in service. The UHF Follow-On satellites replace the Fleet Satellite Communications (FLTSATCOM) and the Hughes-built Leasat spacecraft.

In July 1988, the company won the competition for a fixed-price contract awarded by the Program Executive Office for Space, Communications, and Sensors in Washington, D.C. The initial agreement called for the company to build and launch one satellite, with options for nine more. Options for spacecraft 2 and 3 were exercised in May 1990; for 4, 5, and 6 in November 1990; and for 7, 8, and 9 in November 1991. In January 1994, the customer extended the contract by ordering a 10th satellite and launch services, bringing the total value to $1.7 billion.

In March 1996, under a contract modification for $150 million, the Navy ordered a high-power, high-speed Global Broadcast Service (GBS) payload to be incorporated onto F-8 through F-10. This GBS package is revolutionizing communications for the full range of the Defense Department's high-capacity requirements, from intelligence dissemination to quality-of-life programming. The first GBS payload was put into service in 1998, and the final one was launched in November 1999.

In November 1999, the Space and Naval Warfare Systems Command's Communications Satellite Program Office added an 11th satellite to the contract. In January 2001, Boeing was authorized to begin production on that 11th spacecraft, which is scheduled to launch in 2003. This will help sustain the constellation into the latter part of the decade.

The UFO spacecraft has proven to be a very flexible platform for the evolution of critical advanced DOD communications services. The satellites are versions of the body-stabilized, three-axis HS-601 model. The spacecraft was introduced in 1987 to meet anticipated requirements for high-power, multiple-payload satellites for such applications as UFO, direct television broadcasting to very small terminals, private business networks, and mobile communications.

The HS-601 satellite comprises two main modules. The bus module houses the bus electronics, propulsion subsystem, and battery packs. The payload module contains the communications equipment and antennas.

The UFO satellites are manufactured in El Segundo, California. Using a building-block approach, Boeing and the Navy enhanced the constellation's capabilities in stages. Satellites F-1 through F-3 carry UHF and SHF (super-high frequency) payloads to provide mobile communications and fleet broadcast services. Starting with F-4, an additional EHF (extremely high frequency) payload was added to provide protected communications. F-7 introduced an enhancement to the EHF package that essentially doubles capacity. The SHF payload is replaced by the high data rate GBS package on F-8 through F-10. F-11 carries the enhanced EHF package and an upgraded UHF payload as well.

The UFO satellites offer increased communications channel capacity over the same frequency spectrum used by previous systems. Each spacecraft has 11 solid-state UHF amplifiers and 39 UHF channels with a total 555 kHz bandwidth. The UHF payload comprises 21 narrowband channels at 5 kHz each and 17 relay channels at 25 kHz. In comparison, FLTSATCOM offers 22 channels. The F-1 through F-7 spacecraft include an SHF subsystem, which provides command and ranging capabilities when the satellite is on station as well as the secure uplink for Fleet Broadcast service, which is downlinked at UHF.

The Navy added an extremely high frequency communications package beginning with the fourth spacecraft. This addition includes 11 EHF channels distributed between an earth coverage beam and a steerable 5 spot beam and is compatible with Milstar ground terminals. The EHF subsystem provides enhanced antijam telemetry, command, broadcast, and fleet interconnectivity communications, using advanced signal processing techniques. The EHF Fleet Broadcast capability supersedes the need for the SHF fleet uplink. Beginning with UFO F-7, the EHF package was enhanced to provide 20 channels through the use of advanced digital integrated circuit technology.

F-11 will be most similar to F-7, providing UHF and enhanced EHF communications. The UHF payload incorporates a new UHF digital receiver, providing two additional UHF channels and greater flexibility in configuring communication services.

The first seven satellites and F-11 measure more than 60 feet long from the tip of one three-panel solar array wing to the tip of the other. These arrays generate a combined 2,500 Watts of electrical power on the first three satellites, 2,800 Watts for F-4 through F-7 and F-11, and 3,800 Watts for F-8 through F-10 with GBS.

The arrays are folded against the spacecraft bus for launch, forming a cube roughly 11 feet per side. The satellites weigh an average of 2,600 pounds with the UHF payload, 3,000 pounds with the additional EHF payload, and 3,400 pounds with the GBS payload.

The Atlas rocket series was chosen to provide the launches from Cape Canaveral, Fla. An Atlas-3B-SEC launched UFO F-11.

Nation: USA
Type / Application: Communication
Operator: US Navy
Contractors: Boeing
Equipment: UHF, EHF transponders
Configuration: BSS-601
Propulsion: ?
Power: 2 deployable solar arrays, batteries
Lifetime: 15 years
Mass: 3041 kg
Orbit: GEO
Satellite COSPAR Date LS Launch Vehicle Remarks
UFO 11 (UHF-FO 11, USA 174) 2003-057A 18.12.2003 CC SLC-36B Atlas-3B-SEC


  • Boeing: UHF Follow-On
  • Donald H. Martin: Communication Satellites, Aerospace Press, 1991, p 118-120

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