Introduction
Includingstrategiccommunicationsatellitesandtacticalcommunicationsatellites.Theformerprovidesglobalstrategiccommunications,andthelatterprovidesregionaltacticalcommunications,aswellasmobilecommunicationsformilitaryaircraft,ships,vehicles,andevensingle-personterminals.Sincethe1980s,thedistinctionbetweenstrategiccommunicationsatellitesandtacticalcommunicationsatelliteshasnotbeenobvious.Militarycommunicationsrequireswift,accurate,confidentialanduninterruptedcommunications.Comparedwithciviliancommunicationsatellites,modernmilitarycommunicationsatelliteshaveoutstandingcharacteristicssuchasgoodanti-interference,greatermobility,highreliability,andstrongsurvivability.Thesefeaturesarebasedonchoosingdifferentcommunicationsystems,adjustingthetransmissionpowerandreceivingsensitivity,changingtheantennabeamwidthanddirection,signalprocessing(includingfrequencyhopping,demodulation,etc.)andcross-combinedconnectionsontherealplanet,strengtheningtheremotecontrolcommandsystemandadoptingnuclearpowerWaitfortechnologytoachieve.Theconfidentialityofcommunicationismainlyensuredbyspecialprocessingofinformationbygroundcommunicationterminalequipment.
Specificexamples
SovietUnion
ThecommunicationsatellitesusedbytheSovietUnionformilitaryuseincludecommunicationsatellitesinthelowerorbitsofthe"Cosmos"satelliteseries.Thecommunicationssatellites"Lightning"inellipticalorbits,andcommunicationssatellitessuchas"Rainbow","FluorescentScreen"and"Horizon"ingeostationaryorbit.TheUnitedKingdomandtheNorthAtlanticTreatyOrganizationownthe"Skynet"and"Nato"militarycommunicationssatellitesrespectively.
TheUnitedStates
OnOctober29,1982,theUnitedStatesusedthe"Hercules"34Dcarrierrocketandtheinertialfinalstagetosimultaneouslylaunchthe"NationalDefenseCommunicationSatellite"IIIandanother"NationalDefenseCommunicationsSatellite"Ⅱ."The"NationalDefenseCommunicationSatellite"IIIseriessatellitesareadvancedmilitarycommunicationsatellitesthatuseageostationaryorbit.Fourworkingsatellitesandtwosparesatelliteswillbedeployedovertheequatorat54°and175°eastlongitudeand12°and135°westlongituderespectively.Eachsatelliteisequippedwith7transpondersand10differenttypesofantennas,withatotalbandwidthof375MHz.Itcanworkwithmultiplecommunicationsystemssuchasfrequencydivisionmultipleaccess,codedivisionmultipleaccess,andsinglechannelsinglecarrier.Thecommunicationisflexibleandmaneuverable.Andstronganti-interference.Thedual-axisgimbaldiskantennacancontrolthepointbeampointingtomakethecoverageareamoveasneeded;thehornantennaguaranteesglobalcoverage;1setof61feedarrayreceivingantennasand2setsof19feedarraytransmittingantennascanbebasedonThesizeandshapeofthecoverageareaneedtobechanged,andthepowercanbeoptimallyallocated,soithasthedualfunctionsofglobalstrategiccommunicationsandlocaltacticalcommunications.Thegaincontrolrangeofthecommunicationtranspondercanreach39decibels.Thechannelswitchontheapplicationsatellitecanbecross-connectedwithvarioustransceiverantennacombinationsthroughgroundremotecontrolcommands,whichimprovesthereliabilityandflexibilityofcommunication.TheSandX-banddualremotecontrolcommandsystemstrengthensthesurvivabilityofthesatellite.Thesatellite'spubliccabindesign(seespacecraftdesign)notonlysimplifiestesting,butalsofacilitatestroubleshooting,andcanalsoshortenthesatellitedevelopmentcycle.Itcanbelaunchedbythe"Hercules"carrierrocketorspaceshuttle,anditalsohasastructuralinterfaceforlaunchingtwosatellitesatthesametime.
Thefirstcommunicationssatellite
Theworld’sfirstcommunicationssatellitewasthe"Skol"satellitelaunchedbytheUnitedStatesonDecember18,1958.Thisisanexperimentalsatellite,andthesatellitesuccessfullysentbacktoEarththeChristmasmessageofthenUSPresidentEisenhower.Theworld'searliestgeosynchronousorbitcommunicationsatelliteistheUS"Xinkang"satellite.OnFebruary14,1963,thelaunchof"Xinkang"1wasonlyapartialsuccess.The"Xinkang"2launchedonJuly26,1963wasacompletesuccess.Atthattime,itwasmainlyusedforcombatcommunicationsbetweentheinvadingUSforcesandthePentagon.Sincethen,satellitecommunicationssatelliteshavetheadvantageofalargecommunicationsrange.Threesatellitesaredeployedatequaldistancesovertheequatortoachieveglobalcommunicationsexceptforthenorthandsouthpoles.Chinalaunchedexperimentalandpracticalgeostationarysatellitesin1984and1986.
Frequencybandsused
Militarycommunicationsatellitesaremovingtowardshigherfrequencybands(upperandlowerlines44/20GHz)inthefuture.Choosingahigherfrequencycannarrowthetransmitandreceivebeams,achievealargefrequencyhoppingrange,reducethepossibilityofeavesdroppingandinterference,andcanalsominiaturizegroundantennasandotherequipment,sothatthecommunicationterminalhasbettermobility.Theshape,sizeanddirectionofthebeamcanbecontrolledbyelectronic,mechanicaloracombinationofthetwo,whichcanfurtherimprovetheflexibilityandanti-interferenceabilityofcommunication,especiallythephasedarrayantennawithcontrollablezeropointcanbecutofffromthecoveragearea.Interferingsignalsatanypointwithin.Thesatelliteadoptsprotectivemeasuresagainstelectromagneticpulseandnuclearradiation,whichcanimprovethesurvivabilityofthesatelliteinthecaseofdirectattackandnuclearexplosion.
Developmenttrend
Frombroadcastingsportsgamestotelemedicine,theapplicationofsatellitecommunicationhasgreatlyreducedthedistancesaroundtheworldandprovidedlight-speedcommunicationacrosscontinents.Now,satellitesarehelpingmilitaryvehicleskeepintouchwiththeoutsideworldfarbeyondthehorizon.
Generally,militaryvehiclesmainlyusethreeradiocommunicationmethodstokeepintouchwithsoldiers,commanders,andvehiclesofothertroops.Thesethreecommunicationmethodsinclude:highfrequency(referredtoasHF,electromagneticspectrumrangefrom3MHzto30MHz)radiocommunication,veryhighfrequency(referredtoasVHF,electromagneticspectrumrangefrom30MHzto300MHz)radiocommunication,andultra-highfrequency(ReferredtoasUHF,theelectromagneticspectrumrangesfrom300MHzto3000MHz)radiocommunication.Amongthethreeradiocommunicationmethods,onlyhigh-frequencycommunicationprovidesBLOSradiocoverage.Thisisbecausehigh-frequencytransmissionrequirestheuseoftheionosphere.Theionosphereisapartiallyionizedatmosphericregionlocatedatanaltitudeof85kilometersto660kilometers.Itislikeatrampoline,throughwhichhigh-frequencysignalscanbecontinuouslyreflectedtoreachthedestination.However,althoughhigh-frequencyradiocommunicationcanprovideaverylargecommunicationdistance,thedata,imageandvoicetraffictheycanhandleisextremelylimited.Onthecontrary,VHFandUHFradiocommunicationmethodscanhandlealargeamountofvoice,dataandimages,buttheyonlyhaveasmallcommunicationdistancebecausetheycanonlyprovideline-of-sightcommunication.Inshort,high-frequencyradiocommunicationmethodsprovidepeoplewithlong-distancecommunication,buttheirbandwidthislimited;VHFandUHFradiocommunicationmethodsprovidepeoplewithhighbandwidth,buttheircommunicationdistancesarelimited.
Suchbasicprinciplesofphysicshaveannoyedthearmiesofallcountriesintheworld.Infact,itisunlikelythathigh-frequency,VHFandUHFcommunicationperformancewillchangesoon,unlessthelawsofphysicshaveundergonemajorchanges,butfornow,thisisclearlyunlikely.However,thearmedforcesofallcountriesintheworldneedtoprocessmoreandmorelargeamountsofinformation.Atpresent,theymainlyuseelectronicbattlemanagementsystems(BMSforshort)withcommandandcontrolcapabilities,aswellaslargeamountsofdatacollectedbyunmannedaerialvehicles(UAV)andsoldierphotoelectricsystems..
Oneofthewaystosolvethisradiocommunicationproblemissatellitecommunication(SATCOMforshort).Theuseofsatellitecommunicationscantransmitalargeamountofvoice,dataandimagesaroundtheworld,becausethesesignalscanbetransmittedtothesky,bouncedbysatellites,andreachtheirdestinations.Soldiersnowadaysareequippedwithsatellitecommunicationterminals.Theycancarrythemwheretheyneedthemandsetthemupproperlytoprovidethemselveswithbeyond-the-horizoncommunication.SoldiersarealsoincreasinglybenefitingfrompersonalsatellitecommunicationterminalsbecauseofcommandTheMinistrycanusefixedantennastomeettheirsatellitecommunicationneeds.Theseareallgood,butwhataboutmilitaryvehicles?Theyalsoincreasinglyneedtousesatellitecommunicationstoenjoyhigh-bandwidthcommunications.Forthisreason,somemajorcompaniesaroundtheworldareprovidingmobilesatellitecommunicationsterminalsforstationaryormovingwheeledortrackedmilitaryvehicles.
AdevelopmenttrendofmobilesatellitecommunicationsinthefutureistouseKa-bandmoreandmore.Asmentionedabove,manyusersofmobilesatellitecommunicationsystemsareequippedwithmobilesatellitecommunicationterminalsthatoperateintheX-bandandKu-band.TheproblemwithusingX-bandformilitarycommunicationsisthatthereisonlyabout500MHzofspectrumallocation,whichmeansthatitisfarfrommeetingthehighdemandforsatellitecommunicationsservices.AdoptingKu-bandprovidesapotentialsolution,butitisalsodifficulttomeetthegrowingneedsofmilitaryandcommercialsatellitecommunicationsusers.Therefore,seekingnew,underutilizedradiofrequencyspectrumwillbecomemoreandmoreurgent.Inthenextfewyears,theKa-bandcanprovidemuch-neededspaceforsomemilitarysatellitecommunicationsusersinthisregard,whetheritismobileorothermeans.