Communications satellite

Introduction

Communicationssatellite:Anartificialearthsatelliteusedasaradiocommunicationrelaystation.Thespacepartofasatellitecommunicationsystem.Communicationsatellitestransmitradiosignalstorealizecommunicationbetweensatellitecommunicationearthstations(includingmobilephoneterminals)orbetweenearthstationsandspacecraft.Communicationsatellitesaredividedintogeostationaryorbitcommunicationsatellites,largeellipticalorbitcommunicationsatellites,mediumorbitcommunicationsatellitesandloworbitcommunicationsatellitesaccordingtodifferentorbits;accordingtodifferentserviceareas,theyaredividedintointernationalcommunicationsatellites,regionalcommunicationsatellitesanddomesticcommunicationsatellites;accordingtotheirpurposeItisnotdividedintomilitarycommunicationsatellites,civiliancommunicationsatellitesandcommercialcommunicationsatellites;accordingtothedifferenttypesofcommunicationservices,itisdividedintofixedcommunicationsatellites,mobilecommunicationsatellites,TVbroadcastingsatellites,maritimecommunicationsatellites,trackinganddatarelaysatellites;accordingtothenumberofusesThedifferenceisdividedintodedicatedcommunicationsatellitesandmulti-purposecommunicationsatellites.Ageostationaryorbitcommunicationsatellitecancoverabout40%oftheearth'ssurface,enablinganyground,sea,oraircommunicationstationsinthecoverageareatocommunicatewitheachotheratthesametime.Threegeostationaryorbitcommunicationsatellitesdistributedatequalintervalsovertheequatorcanrealizeglobalcommunicationsexceptforpartsofthepoles.Communicationsatellitesareoneoftheearliestandmostwidelyusedsatellitesintheworld.ManycountriessuchastheUnitedStates,theformerSovietUnion/RussiaandChinahavealllaunchedcommunicationsatellites.

Asaradiocommunicationrelaystation.Acommunicationssatelliteislikeaninternationalmessenger,collectingallkindsof"letters"fromtheground,andthen"delivering"themtousersinanotherplace.Sinceitisa"station"atanaltitudeof36,000kilometers,its"delivery"coverageisparticularlylarge,andasinglesatellitecanberesponsibleforcommunicationon1/3oftheearth'ssurface.Ifthreecommunicationsatellitesareevenlyplacedonthegeostationaryorbit,globalcommunicationscanbeachievedinadditiontothenorthandsouthpoles.Whenasatellitereceivesaweakradiosignalfromagroundstation,itwillautomaticallyturnitintoahigh-powersignal,andthensendittoanothergroundstation,ortoanothercommunicationsatellite,andthensendittotheearth.Ononesideofthegroundstation,inthisway,wereceivedsignalssentfromfaraway.

Communicationsatellitesgenerallyuseageostationaryorbit,whichislocated35,786kilometersabovetheearth'sequator.Onthisorbit,thesatelliterevolvesaroundtheearthfromwesttoeastataspeedof3,075meterspersecond,andthetimetoorbittheearthis23hours,56minutesand4seconds,whichisexactlythesameasthetimefortheearthtorotateonce.Therefore,fromtheground,thesatelliteimagehangsintheskyanddoesnotmove,whichmakestheworkofthegroundreceivingstationmuchmoreconvenient.Theantennaofthereceivingstationcanbefixedlyalignedwiththesatellite,anditcancommunicatedayandnightwithoutinterruption.Thereisnoneedto"shake"aroundliketrackingthosemovingsatellites,sothatthecommunicationtimeisintermittent.Communicationsatelliteshaveundertakenallintercontinentalcommunicationservicesandtelevisiontransmissions.

Definition

Communicationsatellite:anartificialearthsatelliteasaradiocommunicationrelaystation.Communicationsatellitesrealizeradiocommunicationbetweensatellitecommunicationearthstationsorbetweenearthstationsandspacecraftbyretransmittingradiosignals.Communicationsatellitescantransmitinformationsuchastelephone,telegraph,fax,dataandtelevision.Fortheentiresatellitecommunicationsystem,wecallthecommunicationsatelliteanditsmeasurementandcontrolstationthespacesegmentofthecommunicationsystem.

Thisdefinitioniseasyforeveryonetounderstand.Thereisanewterm-relaystation.Toexplaintoeveryone,arelaystationisa"radiostation"thatisresponsibleforreceivingandretransmittingradiosignals.Youcanthinkoftherelaystationasa"long-distancebusstation"forradiosignals.Radiosignalscanbe"refueledortransferredtoothertrains"attherelaystation,sothattheycan"run"farther.ThecommunicationsatelliteisshowninFigure1.

Chinesename:CommunicationSatellite

Foreignname:CommunicationSatellite

Alternativename:None

Applicationdisciplines:informationcommunication,satellitecommunication

Features:radiocommunications,relaystations,artificialearthsatellites

Developmenthistory

Artificialearthsatellitesusedasradiocommunicationrelaystationsinearthorbitarecalled"communicationsatellites"".Communicationsatellitesreflectorforwardradiosignalstorealizecommunicationbetweensatellitecommunicationearthstationsorbetweenearthstationsandspacecraft.Communicationsatellitesarethespacepartofvarioussatellitecommunicationsystemsorsatellitebroadcastingsystems.Ageostationaryorbitcommunicationsatellite(referredtoasa"stationarycommunicationsatellite")cancoverabout40%oftheearth'ssurface,enablinganyground,sea,oraircommunicationstationsinthecoverageareatocommunicatewitheachotheratthesametime.Threegeostationarycommunicationsatellitesdistributedatequalintervalsovertheequatorcanrealizeglobalcommunicationexceptforpartsofthetwopoles.InDecember1958,theUnitedStateslaunchedtheworld'sfirstexperimentalcommunicationssatellite.In1963,theUnitedStatesandJapancarriedoutthefirsttelevisiontransmissionacrossthePacificthroughthe"Relay1"satellite.OnAugust19,1964,theUnitedStatessentthe"Xinkang3"satellitedirectlyovertheequatorneartheinternationaldateline,makingitthefirsttruegeostationarycommunicationssatellite,andsuccessfullybroadcastTokyousingthissatelliteTherealityoftheOlympics.OnApril6,1965,theUnitedStatessuccessfullylaunchedtheworld'sfirstpracticalgeostationaryorbitcommunicationsatellite:Int'lCommunicationSatellite1.Communicationsatellitesareoneoftheearliestandmostwidelyusedsatellitesintheworld.Manycountrieshavelaunchedcommunicationsatellites.Communicationsatellitesgenerallyconsistofasatellitestructure,powersupplysystem,temperaturecontrolsystem,attitudecontrolsystem,antennasystem,transpondersystem,etc.Accordingtotheorbit,itcanbedividedintogeostationarycommunicationsatellitesandnon-stationarycommunicationsatellites;accordingtothedifferentserviceareas,itcanbedividedintointernationalcommunicationsatellites,regionalcommunicationsatellitesanddomesticcommunicationsatellites;accordingtothepurpose,itcanbedividedintodedicatedcommunicationsatellitesandmulti-purposecommunicationsatellites.Communicationsatellitesbringgreatsocialandeconomicbenefits,andsatelliteTVisoneofthemainfunctionsofcommunicationsatellites.Amongthevarioussatellitesstillinorbitandinuse,thenumberofcommunicationsatellitesisthelargest,reachingabout200.Inadditiontothecommunicationsatellitesoperatedbyvariouscountries,someinternationalorganizationsalsooperatemanycommunicationsatellitesforcommercialoperations,themostfamousofwhichistheInternationalCommunicationSatelliteOrganization.Theinternationalcommunicationsatellitesdeveloped,launchedandoperatedbytheInternationalTelecommunicationsSatelliteOrganizationhavedevelopedtotheeighthgeneration,andeachgenerationhasimprovedinsize,weight,technology,communicationcapabilities,andsatellitelife.Communicationsatellitesarearevolutionaryinformationdisseminationtool,whichhasrevolutionizedhumansociety,economy,cultureandpeople'slifestyles.Thedevelopmentofsatellitecommunicationscanpromotethedevelopmentoftheoverallsocialcommunicationsindustry.Theuseofcommunicationsatellitestoestablishacommunicationsystemhasashortconstructionperiod,lessinvestment,andisnotorlessrestrictedbygeographicalconditions,anditssuperiorityisunmatchedbyanyothercommunicationmeans.

Classification

Accordingtodifferentstandards,communicationsatellitescanbedividedintodifferenttypes.

2.1Whetheracommunicationtransponderisincluded

Accordingtowhetheracommunicationtransponderisincluded,communicationsatellitesaredividedinto:

1)Passivecommunicationsatellites:onlyforreflectionSatellitesforradiosignals.Passivecommunicationsatellitesarenolongerindevelopmentandresearchbecauseoftheirveryweakreflectedsignalsandpoorcommunicationquality.

2)Activecommunicationsatellite:Atransponderwithamplificationandfrequencyconversionfunctions,whichtransmitsradiosignalsthroughthetransponder.InDecember1958,theUnitedStateslaunchedtheworld'sfirstlow-orbitexperimentalcommunicationssatellite"Scor".Itisanactivecommunicationsatellite.

2.2Differentorbitsofoperation

Accordingtothedifferentorbitsofcommunicationsatellites,communicationsatellitescanalsobedividedinto:

1)Low-orbitcommunicationsatellites(LEO);

2)MediumOrbitCommunicationSatellite(MEO);

3)HighOrbitSynchronousCommunicationSatellite(GEO).

2.3Attitudestabilizationmethods

Accordingtotheattitudestabilizationmethodsofcommunicationsatellites,communicationsatellitesaredividedinto:

1)Spin-stabilizedsatellites:satellitespassalongfixedThewayofaxisspinkeepsthesatellite'sspatialpositioning.

2)Three-axisstabilizedsatellite:ThethreeaxesX,Y,andZareperpendiculartoeachothertomaintainthesatellite'sspatialpositioning.

2.4Servicefrequencybandsused

Accordingtotheservicefrequencybandsusedbycommunicationsatellites,communicationsatellitescanbedividedinto:

1)Single-bandsatellites:CommunicationsatellitesuseUHF,L,S,C,X,Ku,Kaandotherfixedfrequencybands.

2)Multi-bandintegratedsatellite:acommunicationsatellitethatusestwofrequencybandsormorethantwofrequencybands.

2.5Serviceareasofsatellites

Accordingtotheserviceareasofcommunicationsatellites,communicationsatellitesaredividedinto:

1)Internationalcommunicationsatellites

2)Regionalcommunicationsatellites

3)Domesticcommunicationsatellites

2.6Serviceobjectsofsatellites

Accordingtotheserviceobjectsofcommunicationsatellites,communicationsatellitesaredividedinto:

1)Commercialcommunicationssatellites

2)Militarycommunicationssatellites

3)Scientificexperimentalcommunicationssatellites

2.7Professionalusesofsatellitesh3>

Accordingtotheprofessionaluseofcommunicationsatellites,communicationsatellitesaredividedinto:

1)Directbroadcastsatellites:broadcastTVandradioprogramsdirectlytothepublic.

2)Maritimecommunicationssatellite:usedformaritime,airandlandcommunications,takingintoaccountrescueandnavigationtasks.

3)TrackingandDataRelaySatellite(TDRSS):usedformeasurementandcontrolandrelaytransmissionofdatainformationbetweenspacecraftandearthstations;capableofmeasurementandcontrolofspacecraftinhigh,mediumandloworbits.

4)Navigationandpositioningsatellites

5)Remotesensingsatellites.

Trend

Developmenttrend:Afteryearsofdevelopment,varioustechnologiesofcommunicationsatelliteshavebeenrelativelymature,andGPSnavigationandsatelliteTVhaveenteredthousandsofhouseholds.Satellitesinsynchronousorbitarealreadyvery"crowded."Thedevelopmentresearchofcommunicationsatellitesismainlyinthefollowingaspects:

1.Howtoexpandnewfrequencybandswhencommunicationsatellitesare"crowded"andpronetointerference;

2Howtousethelimitedsatellitespacetodeveloptheinformationtechnologyonthesatellite;

3.Howtoextendthetimeofthesatelliteinspaceandhowtoextendtheworkinglifeofthesatellite;

4.HowtoimprovethecommunicationTheaccuracyofthesatelliteantennapointing.