SATELLITESIn 1976, three satellites were placed into orbit overthe Atlantic, Pacific, and Indian Oceans. Thesesatellites, called MARISATs, were procured by andare managed by the COMSAT General Corporation.Each satellite has three uhf channels for military use(one wideband 500-kHz channel and two narrowband25-kHz channels). The uhf section of each satellite isleased to the Navy for communications. To distinguishthe special management and control functions forcommunications on these uhf channels, the Navy hasgiven the leased MARISAT satellite assets the nameGAPFILLER.Current planning calls for no Navy use ofGAPFILLER satellites after the mid-1990’s. Satellitecoverage will then be provided by a combination ofF L T S A T and L E A S A T until the new U H FFOLLOW-ON (UFO) satellites are placed intoservice. The Navy plans to have two operationalsatellites in each of four satellite coverage areas. Eachsatellite coverage area can be terminated in at least twoNCTAMS, allowing around-the-world connectivity.You can see this connectivity in figure 3-16.FLTSATCOM SATELLITEThe FLTSATCOM satellite consists of two majorparts: a payload module that includes the antennas anda space craft module with a solar array. The payloadmodule contains the uhf, shf, and S-band (tracking,telemetry, and command) communications equipmentantennas. The communications equipment is mountedinternally on side panels that cover this section of thesatellite.The space craft module contains nearly all othersubsystem equipment, including sensors, attitude andvelocity control, telemetry, tracking and command,and electrical power distribution. The spacecraft isstabilized on three axes, and the body-fixed antennasare kept pointing at the sun by a clock drive. AFLTSATCOM satellite is shown in figure 3-17.E a c h F L T S A T C O M s a t e l l i t e c a n r e l aycommunications on 23 separate uhf channels. Of the23 channels, 10 are 25-kHz channels, 12 are 5-kHzchannels, and one is a 500-kHz channel. The ten 25-kHz channels are dedicated for Navy use. Each 25-kHzuhf down-link channel has a separate transmitter.Channel one, used in primary mode for Fleet Broadcasttransmissions, incorporates signal processing withinthe satellite (the shf up-link signal is translated to uhfFigure 3-17.—FLTSATCOM satellite.for down-link transmission). In addition, two of theFLTSATCOM satellites have ehf packages attached.FLTSAT Extremely-High-Frequency Package(FEP)The Fleet Satellite (FLTSAT) Extremely-High-Frequency (EHF) Package (FEP) provides ehfcommunications capability for Army, Navy, and AirForce ground, airborne, and ocean-going terminals.Two FEPs are currently in orbit, carried aboard twomodified uhf FLTSATs, numbers seven and eight.FEP operates at ehf frequencies of approximately20-GHz on the down-link and 44-GHz on the up-link.It has two antenna beams: (1) a dual-frequency spotbeam steerable by ground command, and (2) an earthcoverage beam that uses separate horn antennas fortransmit and receive.LEASAT SATELLITEThe LEASAT satellite has seven 25-kHz uhfdown-link channels, one 500-kHz wide-band channel,and five 5-kHz channels. One of the seven 25-kHzdown-link channels is used for Fleet Broadcast.The broadcast up-link is shf, with translation touhf taking place in the satellite. The remaining3-21
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