UHF Follow-On satellite

This article is about the U.S. DoD UHF Follow-On satellite system. For orbiting unidentified objects, see Unidentified flying object.

Ultra High Frequency Follow-On (UFO) satellite system is a United States Department of Defense (DoD) program sponsored and operated by the United States Space Force to provide communications for airborne, ship, submarine and ground forces. The UFO constellation replaced the U.S. DoD Fleet Satellite Communications System (FLTSATCOM) constellation and consisted of eleven satellites. The ground terminal segment consists of equipment and resident personnel at existing satellite communication stations. The satellites are controlled by the 10th Space Operations Squadron (Space Delta 8) located at the Naval Base Ventura County, Point Mugu, California.

Ultra High Frequency Follow-On

Artist's impression of a UHF Follow-On satellite in orbit
Country of origin	United States
Operator	United States Space Force
Applications	Military communications
Specifications
Bus	HS-601
Launch mass	2,844 kg (6,270 lb)
Regime	Geosynchronous orbit
Design life	14 years (planned)
Production
Status	Active
Built	11
Launched	11
Lost	1
Maiden launch	25 March 1993
Last launch	18 December 2003

Satellite description

The Ultra high frequency (UHF) satellites primarily served tactical users. UFO provided almost twice as many channels as FLTSATCOM and has about 10% more power per channel. THe satellites were built by Boeing Integrated Defense Systems (formerly Hughes Space and Communications Company) and were based on the 601 series of communciations satellites.^[1]

The Extremely high frequency (EHF) package on satellites four through eleven have an Earth coverage beam and a steerable five-degree spot beam that enhances its tactical use. The EHF capability also allows the UFO network to connect to the strategic Milstar system. Satellites eight, nine and ten also carry the Global Broadcast Service antennas that operate in the Ka-band. The Atlas was the launch vehicle of choice; however, space shuttle compatibility existed.^[2] The UFO bus and payload weigh 2,844 kg (6,270 lb).^[3] The solar panels spans 18.4 m (60 ft) and produces 2,500 watts at the end of the planned 14-year lifetime. The UHF system supports stationary and mobile users including manportable, ships, submarines, aircraft and other mobile terminals. The UFO Follow-On system is scheduled for replacement by the Mobile User Objective System (MUOS).^[4]

Block Upgrades

Block 1 satellites had UHF and SHF communications. Block 2 satellites, starting with UHF 4, added extremely high frequency package with 11 channels. Block 3 satellites replaced the SFH communications with Ka-band transponders.^[5] Block 4 satellite incorporated a digital UHF receiver and two additional UHF channels.^[6]

Launch

First launch of the UFO took place on 25 March 1993, with constellation completion dependent on replacement needs for the aging FLTSATCOM constellation.^[7]

Table of Satellites

Launch	Designation	COSPAR ID	Launch Vehicle	Launch Date	Block	Status
1	UHF F/O 1	1993-015A	Atlas 1	1993-03-25	1	Placed in unusable orbit[3]
2	UHF F/O 2	1993-056A	Atlas 1	1993-09-03[8]	1
3	UHF F/O 3	1994-035A	Atlas 1[9]	1994-06-24	1
4	UHF F/O 4	1995-003A	Atlas 2[10]	1995-01-29	2
5	UHF F/O 5	1995-027A	Atlas 2	1995-05-31	2
6	UHF F/O 6	1995-057A	Atlas 2	1995-10-22	2
7	UHF F/O 7	1996-042A	Atlas 2	1996-07-25	2
8	UHF F/O 8	1998-016A	Atlas 2[11]	1998-03-16	3
9	UHF F/O 9	1998-058A	Atlas 2A	1998-10-20	3
10	UHF F/O 10	1999-063A	Atlas 2A	1998-11-23	3
11	UHF F/O 11	2003-057A	Atlas 3B-SEC[6]	2003-12-18	4