UHF Follow-on (UFO)

The US Navy sponsored UHF Follow-on (UFO) replaced FLTSATCOM and LEASAT, providing almost twice as many channels and some 10% more power per channel, and was compatible with the terminals in service. The first UFO failed on launch on 25 March 1993; UFO-2 (38 UHF channels) was successfully launched on 3 September 1993 to begin a planned nine-satellite constellation with satellites arranged in pairs providing global coverage. UFO-3 was launched in January 1994 and was operational until Jun 1995. UFO-4 and UFO-6 (38 UHF channels plus an EHF payload) were launched in 1994-5, UFO-7 (34 UHF channels and enhanced EHF) in 1996, UFO-9 in October 1998 and UFO-10 (both with 38 UHF channels, enhanced EHF, and Ka-band GBS payload) in December 1999. The final satellite, UFO-11 (59 UHF channels enhanced EHF), was launched on 18 December 2003. UFO-4 and UFO-9 failed in 2007.

UFO provided global communications to maritime forces replacing the 5-kHz and 500-kHz FLTSATCOM channels with 1×25-kHz Fleet Broadcast channel, 21×5-kHz and 17×25-kHz relay channels on 11 FDMA solid state transponders with a total of 530 kHz bandwidth. UFO coverage areas were similar to those of WGS.

Each satellite provided a total of approximately 590 kbps DAMA (uplink 292–317 MHz and downlink 243–270 MHz). The solar panels produce 2.5 kW at end of life (14 years). Each transponder was originally intended for use by a single user or network (most other satellites use wide-band transponders shared by many networks).

The satellites are nuclear-hardened (EMP protected), and each satellite has one jam-resistant SHF/EHF uplink and 25-kHz UHF downlink for fleet broadcast.

UFO-1 through to UFO-2 carried UHF and SHF payloads. From UFO-4, an EHF payload was added, providing 11 EHF channels distributed over an Earth-coverage beam and a 5° spot beam compatible with Milstar terminals. From UFO-7, enhancements to the EHF payload effectively doubled throughput.

The SHF payload on UFO-1 to UFO-7 provided command and ranging capabilities as well as a secure uplink for Fleet Broadcast, which is downlinked at UHF. From UFO-8 to UFO-11, the SHF payload was replaced by the Global Broadcast package that operates in Ka-band.

The UFO system was replaced by the Mobile User Objective System (MUOS).