Artificial earth satellite

Basicintroduction

Simplyput,theman-madeearthsatelliteissentintospacebyagiantmulti-stagerocketwithhugepropulsionpower.Theworkingprincipleofmulti-stagerocketsisnotcomplicated.Itistoconnectseveralsingle-linerocketsinseriesorparalleltoformalargerocketsystem.Eachofthesestagesisarocketthatcanworkindependently,andtheycompletetheirmissionsinstages.First,thefirststagerocketisignited.Atthistime,theentirerocketrisesintotheair.Whenthepropulsionofthefirststageisexhausted,itsbulkyshellisimmediatelythrownaway,andthenthesecondstagestartstowork.Partoftheweightofthestructureisuseless,sothattheentirerocketislightlyloaded,andthenthesecond-stageshellisthrownaway,andthethird-stageisignited...Thisway,onestepaftertheother,likearelayrace,thelighterthemoreitruns,Runfasterandfaster.Untiltheendofthefinalstageofrocketwork,thesatellitemountedonthefrontendofthefinalstageofrocketwillenterearthorbit.Theearthhasagravitationaleffectonthesurroundingobjects,sothethrownobjectshavetofallbacktotheground.However,thegreatertheinitialvelocityofthethrow,thefarthertheobjectwillfly.WhenNewtonwasthinkingaboutthelawofuniversalgravitation,hehadimaginedthatwhenobjectswerethrownfromamountainatdifferenthorizontalspeeds,thespeedwasgreaterthanthatofeachtime,andthelandingplacewasalsofartherawayfromthefootofthemountain.Ifthereisnoairresistance,whenthespeedishighenough,theobjectwillneverfalltotheground.Itwillrevolvearoundtheearthandbecomeanartificialearthsatelliteorbitingtheearth,referredtoasartificialsatellite.Artificialsatellitesarethespacecraftwiththelargestnumberoflaunches,themostversatile,andthefastestgrowing.OnOctober4,1957,theSovietUnionlaunchedtheworld'sfirstartificialsatellite.Themainequipmentinthissatelliteisachemicalenergybatteryradiotransmitter.Sincethen,theUnitedStates,France,andJapanhavesuccessivelylaunchedartificialsatellites.ChinalaunchedtheDongfanghong1satelliteonApril24,1970.Bytheendof1992,Chinahadsuccessfullylaunched33differenttypesofsatellites.

Artificialsatellitesgenerallyconsistofadedicatedsystemandasecuritysystem.Thededicatedsystemreferstothesystemdirectlyrelatedtothemissionperformedbythesatellite,alsoknownasthepayload.Thededicatedsystemsusingsatellitesincludecommunicationtransponders,remotesensors,navigationequipment,etc.accordingtothevarioususesofsatellites.Thededicatedsystemsofscientificsatellitesarevariousspacephysicalexploration,astronomicalexplorationandotherinstruments.Thededicatedsystemofthetechnicaltestsatelliteisthetestequipmentofvariousnewprinciples,newtechnologies,newschemes,newinstrumentsandnewmaterials.Theguaranteesystemreferstothesystemthatguaranteesthenormaloperationofsatellitesandspecialsystemsinspace,alsoknownastheservicesystem.Therearemainlystructuralsystems,powersupplysystems,thermalcontrolsystems,attitudecontrolandorbitcontrolsystems,andradiomeasurementandcontrolsystems.Forreturningsatellites,thereisalsoareturninglandingsystem.

Theorbitoftheartificialsatellitedependsonthemissionrequirementsofthesatellite.Itisdividedintoloworbit,medium-highorbit,geosynchronousorbit,geostationaryorbit,sun-synchronousorbit,largeellipticalorbitandpolarorbit.Artificialsatellitesorbittheearthatafastspeed.Low-orbitandmedium-highorbitsatellitescanorbittheearthseveraltimestomorethantentimesaday,withoutbeingrestrictedbyterritorial,airspaceandgeographicalconditions,andhaveabroadfieldofvision.Itcanquicklyexchangeinformationwiththeground,includingtheforwardingofgroundinformation,andcanalsoobtainalargeamountofremotesensinginformationoftheearth.Theremotesensingareaof​​asatelliteimageofearthresourcescanreachtensofthousandsofsquarekilometers.

Whenthesatellite'sorbitalaltitudereaches35,800kilometersanditfliesinthesamedirectionastheearth'srotationovertheearth'sequator,thesatellite'srotationperiodaroundtheearthisexactlythesameastheearth'srotationperiod,andtherelativepositionremainsunchanged.Thissatelliteiscalledgeostationaryorbitsatellite,orgeostationarysatelliteforshort.Thissatellitecanrealizetheuninterruptedinformationexchangebetweenthesatelliteandthegroundstation,andgreatlysimplifytheequipmentofthegroundstation..Thevastmajorityoftelevisionrelayandrelaycommunicationsviasatellitesareimplementedbystationarycommunicationssatellites.

Classification

Artificialearthsatellitescanbedividedintothreecategoriesaccordingtotheirpurpose:scientificsatellites,technicaltestsatellites,andapplicationsatellites.

(1)Scientificsatellites

Sciencesatellitesaresatellitesusedforscientificexplorationandresearch,mainlyincludingspacephysicalexplorationsatellitesandastronomicalsatellites,whichareusedtostudytheupperatmosphereandtheearth'sradiationbelt,Earth’smagnetosphere,cosmicrays,solarradiation,etc.,andcanobserveotherstars.

(2)Technicaltestsatellites

Technicaltestsatellitesaresatellitesthatconductnewtechnologytestsortestapplicationsforsatellites.Therearemanynewprinciples,newmaterials,andnewinstrumentsinaerospacetechnology.Whethertheycanbeusedornotmustbetestedinthesky.Theperformanceofanewsatellitecanonlybe“exercised”bylaunchingitintothesky.Application;animalexperimentsmustbecarriedoutbeforehumansgotothesky...Thesearethemissionsoftechnologyexperimentsatellites.

(3)Applicationsatellites

Applicationsatellitesaresatellitesthatdirectlyservehumans.Theyhavethemosttypesandthelargestnumber,including:communicationsatellites,weathersatellites,reconnaissancesatellites,andnavigationSatellites,geodesicsatellites,earthresourcesatellites,interceptionsatellites,etc.

Functionalclassification

Classifiedbythefunctionofspacecraftinorbit,asfarasartificialearthsatellitesareconcerned,theycanbedividedintofourcategories:observationstation,relaystation,referencestationandorbitalweapon.Eachcategoryincludesavarietyofspacecraftfordifferentpurposes.

Observationstation

Thesatelliteisinorbit.Fortheearth,itstandstallandseesfar(largefieldofview).Itisveryadvantageoustouseittoobservetheearth.Inaddition,becausesatellitesarenotaffectedbyvariousinterferencesandinfluencesfromtheatmosphereoutsidetheearth’satmosphere,itismoreadvantageoustousethemforastronomicalobservationsthanground-basedastronomicalobservatories.Satellitesbelongingtothisfunctionhavethefollowingtypicaluses.

Reconnaissancesatellites

Reconnaissancesatelliteswerelaunchedfirstamongvariousapplicationsatellites(launchedin1959),andthenumberoflauncheswasalsothelargest.Therearetwotypesofreconnaissancesatellites:photographicreconnaissanceandelectronicreconnaissancesatellites.

Photoreconnaissancesatellitesaresatellitesthatuseopticalequipmenttotakepicturesofgroundtargets.Sincethe1920s,aboutone-thirdofthemilitarysatelliteslaunchedbytheformerSovietUnionandtheUnitedStateseachyearhavebeenusedforvariousformsofphotographicreconnaissance.Theyhaveconductedgeneralsurveysanddetailedsurveysinlow-Earthorbit.

Electronicreconnaissancesatellitesuseon-boardelectronicequipmenttointerceptelectromagneticwavespropagatinginspaceandforwardthemtothegroundtoobtainenemyintelligencethroughanalysisanddeciphering.Thepurposeofelectronicreconnaissanceistodeterminethelocationandcharacteristicparametersofothersystemssuchasairplanesandradars,andtoeavesdroponotherparties'radioandmicrowavecommunications.Electronicreconnaissancesatellitesaccomplishthesemissionswithradiodetectionandrecordingequipment.

Inshort,whetherformilitarystrategicreconnaissanceormilitarytacticalreconnaissance,theintelligenceinformationprovidedbyreconnaissancesatellitesplaysanimportantroleintheformulationandmilitaryoperationsoftheUnitedStatesandtheformerSovietUnion.inaccordancewith.Accordingtoreports,nearly70%ofthemilitaryintelligenceoftheUnitedStatesandtheformerSovietUnioncomesfromreconnaissancesatellites.

Meteorologicalsatellites

Meteorologicalsatellitesusevariousmeteorologicalremotesensorscarriedtoreceiveandmeasurevisiblelightradiationandinfraredradiationfromtheearth,oceanandatmosphereAndmicrowaveradiationinformation,andthenconvertthemintoelectricalsignalsandsendthemtothegroundreceivingstation.Basedonthecollectedinformation,meteorologistsprocessthedatatoobtainglobalatmospherictemperature,humidity,windandothermeteorologicalelements.Globalweatherdatacanbeobtainedwithinafewhourstomakelong-termweatherforecasts,determinethelocationandchangesoftyphooncenters,andforecasttyphoonsandotherstorms.Meteorologicalsatellitesplayagreatroleinensuringthesafetyofnavigationandaviation,andensuringtheproductionofagriculture,fisheriesandanimalhusbandry.

Meteorologicalsatelliteshavedevelopedfromsimplemeteorologicalexperimentstocomprehensiveapplicationsinmultipledisciplinesandfields;fromlow-orbitsystemstohigh-orbitsystems,formingaglobalmeteorologicalsatelliteobservationnetwork.Theapplicationofmeteorologicalsatellitesinmilitaryactivitiesisalsoincreasing.Somecountrieshaveestablishedaglobalmilitarymeteorologicaldatacollectionsystemtoprovidemilitaryunitswithreal-timeornon-real-timemeteorologicaldata.

Withthefurtherdevelopmentofaerospacetechnology,meteorologicalremotesensorswilldevelopinadiversifiedandhigh-precisiondirection,greatlyenrichingthecontentofweatherforecastingandimprovingforecastingaccuracy.Atthesametime,thecloudimagesprovidedbymeteorologicalsatelliteswillalsodevelopfromstaticcloudimagestodynamiccloudimages,whichwillcauseamajorbreakthroughinthedevelopmentofmeteorologicalsatellites.

EarthResourceSatellites

Resourcesatellitesaredevelopedonthebasisofreconnaissancesatellitesandmeteorologicalsatellites.Themulti-spectralremotesensormountedonthesatelliteisusedtoobtaintheelectromagneticwavesofvariousbandsradiatedandreflectedbythegroundtarget,andthentransmittedtotheground,andthenprocessedintousefuldataabouttheearth'sresources.Theyincludegroundandunderground,landandsea,andsoon.

Earthresourcesatellitescanbewidelyused:undergroundmineraldeposits,marineresourcesandgroundwatersourcesurveys;landresourcesurveys,landuse,regionalplanning;surveysofagriculture,forestry,animalhusbandry,andwaterresourcesforreasonableplanningandmanagement;forecastingGrowingandharvestingofcrops;studyingthegenerationandlandformofnaturalplants;examiningandmonitoringvariousnaturaldisasterssuchaspestsanddiseases,forestfires,floods,etc.;environmentalpollution,marinepollution;measuringwaterandsnowsources;railway,highwayrouting,portconstruction,Coastalutilizationandmanagement,urbanplanning.Earthresourcessatelliteshavegreateconomicvalueandpotentialmilitaryapplications.

Marinesatellites

Theoceanisthecradleoflifeandthehometownofwindandrain.Thecloserelationshipbetweentheoceanandhumansisgraduallybeingrecognized.Theoceancontrolsthecirculationofwaterinnatureandthemovementoftheatmosphere,regulatestheclimateofthecontinent,andprovidescheaptransportationconditionsandhigh-qualityaquaticfood.Therearehugeenergyandmineralresourcesintheocean.

Forthesurvey,research,utilizationanddevelopmentoftheoceanandcoastline,althoughsomedataanddatacanbeobtainedbymeteorologicalsatellitesandearthresourcesatellites,itdoesnotsolvethefundamentalproblems.Forexample,thebandofremotesensorsforresourcesatellitesismainlyinvisiblelight.Andthenear-infraredband,whiletheoceanremotesensorbandismainlyintheinfraredandmicrowavebands.Chinaisnotonlyacontinentalcountry(9,600,000km2ofland),butalsoamaritimecountry(18,000kmofcoastline,4,700,000kmofseaarea,andmorethan4,000,000km2ofeconomicdevelopmentzones).Thedevelopmentofmarinesatellitesisanecessityforthenationaleconomyandmilitary..

Themissionofmarinesatellitesismarineenvironmentalforecasting,includingthebestrouteselectionforocean-goingships,marinefisheryanalysis,offshoreandcoastalmarineresourcesurveys,coastalandoffshoremarineenvironmentalmonitoringandmonitoring,anddisasterforecastingAndearlywarning,marineenvironmentalprotectionandlawenforcementmanagement,marinescientificresearch,aswellasmarinebuoys,stations,shipdatatransmission,maritimemilitaryactivities,etc.Ofcourse,therearefarmoresatellitesasobservingstations.Earlywarningsatellites,nuclearexplosiondetectionsatellites,andastronomicalpredictionsatellites(suchastheUSHubbleSpaceTelescope)allfallintothiscategory.Althoughtheirfunctionshavedifferentfocuses,thebasicobservationprinciplesaresimilar.

Relaystation

Relaystationisakindofsatellitethatamplifiesandrelaysinformationinorbit.Specifically,itisdividedintotwocategories:oneisusedtotransmittelephones,telegraphs,televisionsanddatabetweenlocationsonthegroundfarapart;theotherisusedtotransmittelevisionanddatabetweensatellitesandtheground.Therearethefollowingtypesofsuchsatellites:

Communicationsatellites

Comparedwithordinarygroundcommunicationusingsatellites,ithasthefollowingadvantages:largecommunicationcapacity;Widecoveragearea;longcommunicationdistance;highreliability;goodflexibility;lowcost.Communicationsatellitesgenerallyadoptageostationaryorbit,whichisequivalenttobeingstationaryinthesky.Iftherearethreegeostationaryorbitsatellitesseparatedby120degreesfromeachother,globalcommunicationscanbeachievedexceptforpartsoftheearth’spoles.

Communicationsatelliteshavebeenusedininternational,domesticandmilitarycommunicationsservices,andregionalcommunicationsandsatellite-to-satellitecommunicationshavebeencarriedoutatthesametime.Satellitecommunicationtechnologyhasbeengivenastrongmilitarycolor,anditoccupiesanabsoluteadvantageinstrategicandtacticalcommunications.Theexistinginternationalanddomesticsatellitecommunicationsystemsofvariouscountriesareundertakingmilitarycommunicationtasks.

Communicationsatelliteshaveenteredafairlymaturestageofpracticalapplications,especiallywiththedevelopmentofgeostationaryorbitsatellitecommunicationtechnology,itsapplicationsarebecomingmoreandmoreextensive.Itcanbeusedtotransmittelephones,telegraphs,televisions,newspapers,faxes,voicebroadcasts,timestamps,data,videoconferences,etc.

Broadcastsatellite

Broadcastsatelliteisacommunicationsatellitemainlyusedfortelevisionbroadcasting.ThiskindofbroadcastsatellitecanbroadcastortransmitTVbroadcastprogramstothegroundwithoutanytransitfordirectreceptionbypublicgroupsorindividuals,soitisalsocalledadirectbroadcastsatellite.OrdinaryhomeTVsetswithasmalldiameterantennaandset-topboxcandirectlyreceivelivesatelliteTVbroadcastprograms.

Trackinganddatarelaysatellite

Trackinganddatarelaysatelliteisamajordevelopmentofcommunicationsatellitetechnology.Itusessatellitestotrackandmeasurethepositionofanothersatellite.Thebasicideaistomovethemeasurementandcontrolstationontheearthtoageosynchronousorbittoformasatellite-to-groundmeasurementandcontrolsystemnetwork.Inthisway,itcangreatlyincreasethetrackingandmeasurementarcsoflow-Earthorbitsatellites,suchasmeteorologicalsatellites,reconnaissancesatellites,resourcesatellites,marinesatellites,communicationsatellites,etc.,improveorbitmeasurementaccuracy,andreducethenumberofgroundstations.Inotherwords,trackinganddatarelaysatellitesusegeosynchronousorbitsatellitestorealizethetrackinganddatarelayoflow-orbitsatellitesbythegroundmeasurementandcontrolcenter.

Thedevelopmentoftrackinganddatarelaysatelliteswillchangetheexcessivedependenceofspaceactivitiesongroundmeasurementandcontrol,anditcanalsoovercomethedifficultyofbeingunabletosetupgroundstationsabroad,soithasreceivedgeneralattentionfromtheworld'smajorspacepowers.Chinaisalsoactivelydevelopingthissatellitetechnology.

Inadditiontotheabove-mentionedrelaystationsatellitesystems,countrieshavealsodevelopedandlaunchedothertypesofdedicatedcommunicationsatellitesandradioamateursatellites,suchasmaritimesatellites,satellitecommercialsystems,searchandrescuesystems...

Referencestation

Thiskindofsatelliteisameasurementreferencepointinorbit,soitisrequiredtomeasureitsorbitveryaccurately.Satellitesthatbelongtothisfunctionare:

NavigationSatellite

Thiskindofsatelliteemitsapairofverystableradiowaves,marinevessels,underwaterSubmarinesandmovingbodiesonlandcandeterminetheirpositionbyreceivingradiosignalsemittedbysatellites.Theuseofnavigationsatellitesfornavigationisamajortechnologicalbreakthroughinthehistoryofspaceflight.Satellitescancovertheworldforall-weathernavigationwithhighnavigationaccuracy.

Therearethreetypesofsatellitenavigationandpositioning:Dual-frequencyDopplervelocitymeasurementandpositioningsystem,suchasthe"Midridian"navigationsatellitesystemintheUnitedStates.Thistypeofsatelliteisatwo-dimensionalnavigationandpositioningsystem,whichcanonlybeusedforshipsinthewater,withapositioningaccuracyof30-50m.Thedevelopmentofthe"Meridian"satellitebeganin1958andwasputintousein1964.Itwasoriginallyusedforpositioningofunderwaternuclearsubmarinesandhasbeendiscontinued;thenavigationsatelliteGlobalPositioningSystem(GPS).Usingpseudo-randomcoderanging,thesystemcanperformall-weather,all-weather,real-timethree-dimensionalnavigationandpositioning,withapositioningaccuracyoflessthan10,andisusedforships,aircraft,andland-basedmovingtargets.Thesystemrequires18to24satellitesfornetworking.Russiaalsohasatwo-generationnavigationsatellitesystemsimilartotheUnitedStates;aregionalnavigationandpositioningsystem.3stars(stationaryorbit)provideathree-dimensionalposition.Ifyoulaunchtwostars,youcanonlyprovideatwo-dimensionalposition.Ifyoucanprovideyourownaltitude,youcancalculateathree-dimensionalposition.Thesystemischaracterizedbybeingabletoservemillionsofusersatthesametime,withoutinterferingwitheachother,andhavinggoodconfidentiality.

Geodesicsatellite

Theprincipleofsatellitegeodesyissimilartothatofsatellitenavigation.Sincethemeasurementstationonthegroundisfixed,themeasurementaccuracyishigherthanthatofshipnavigationandpositioning.Theaccuracyachievedbysatellitegeodesyisdozensoftimeshigherthanthatofconventionalgeodeticsurveys.

Geodesicsatellitescancompletegeodeticsurveying,topographicdetermination,mapsurveyingandmapping,earthshapesurveying,aswellasgravityandgeomagneticfielddetermination.

Satellitegeodesyisvaluedinmilitary,scientificresearchandcivilianuse.Manycountrieshavedevelopedandlaunchedgeodesicsatellitesystems.Theuseofsatellitesforgeodesyprovidesmodernmeansforsurveyingandmappingwork,withshortworkcyclesandhighmeasurementaccuracy,whichgreatlysavesmanpower,materialresourcesandfinancialresources.Especiallytoestablishanaccurateglobalgeographiccoordinatesystemorthree-dimensionalmap,theuseofsatellitegeodesyistheonlyfeasiblemeasurementmethod.Withthecontinuousimprovementofscienceandtechnology,theapplicationofgeodeticsatelliteshasbecomemoreandmoreextensive.Forexample,peopleusegeodeticsatellitestomeasurecrustalmovementtomonitorandpredictearthquakes.

Thereareactiveandpassivegeodeticsatellites,whichcanusetriangulation,laserranging,Dopplersystemandothermethodstoachievethepurposeofgeodesy.

Orbitalweapons

Thisisanaggressivelyoffensivespacecraft,whichhasthefunctionsofspacedefenseandspaceattack.Itmainlyincludes:

Interceptingsatellites

Satellitesapproachasaweaponinorbittoidentifyanddestroyenemyspacesystems.ThiskindofsatelliteiscalledItisananti-satellitesatellite.Therearemanywaystointerceptanti-satellitesatellites.Themainonesare:makingtheinterceptingsatellitemeetthetargetsatelliteinspace,andthenexplodetodestroythetarget;launchinganti-satelliteweaponsfromtheinterceptingsatellite,suchaslasers,particles,andmicrowavesandotherdirectedhigh-energybeams.Weapon;theinterceptingsatelliteusesitsownsmallrocketboostertoaccelerateandcollidewiththetargetsatellite;trytomakethetargetsatelliteincapableofworking,suchasusingnuclearradiationtodestroythecircuitandstructureofthetargetsatellite,andspraymaterialonthecameralensofthetargetsatellite,andmanymore.

Asearlyasthelate1950s,theUnitedStatesandtheformerSovietUnionbegantostudyinterceptingsatellites.Russiahasmasteredthetechnologytointerceptsatellitesbelow1,000km,andtheUnitedStatesalsosuccessfullyconductedon-orbitanti-satellitetestsinthe1990s.

Orbitalbombingsystem

Theorbitalbombingsystemisaspace-to-groundoffensiveweapon.Itsmissionistodeploytheweaponintheearth'sorbit.Whenitorbitstheearthtoadesignatedposition,itusesareversethrustretrorockettoslowitdown,loweritsorbit,andfireittowardthetargetaccordingtogroundinstructions.

Orbit

Thereareusuallythreetypesoforbits(exceptlowearthorbits)ofartificialsatellites:geosynchronousorbits,sun-synchronousorbits,andpolarorbits.①Ageosynchronousorbitisaprogradeorbitwhoseoperationperiodisthesameastherotationperiodoftheearth.Butthereisaveryspecialorbit,calledthegeostationaryorbit.Theinclinationofthisorbitiszero,35,786kilometersabovetheearth'sequator.Fromtheeyesofpeopleontheground,thesatellitesinthisorbitarestationary.Generalcommunicationsatellites,broadcastingsatellites,andweathersatellitesusethiskindoforbittobemoreadvantageous.Therearecountlessgeosynchronousorbits,whilethereisonlyonegeostationaryorbit.

②Thesun-synchronousorbitisanorbitwheretheorbitalplanerotatesaroundtheearth’srotationaxis,thedirectionisthesameastheearth’srevolution,andtherotationalangularvelocityisequaltotheaverageangularvelocityoftheearth’srevolution(360degrees/year),anditsheightfromtheearthNomorethan6000kilometers.Thelocaltimewhenthesatellitesorbitingonthisorbitpassthesamelatitudeinthesamedirectionisthesame.Meteorologicalsatellitesandearthresourcesatellitesgenerallyusethisorbit.

③Thepolarorbitisanorbitwithaninclinationangleof90degrees.Thesatellitesinthisorbitmustpassovertheearth’spolesineachcircleandcanoverlooktheentireearth’ssurface.Meteorologicalsatellites,earthresourcesatellites,andreconnaissancesatellitesoftenusethisorbit.

Progradeorbit

Thecharacteristicofprogradeorbitisthattheorbitalinclinationangleislessthan90degreesbetweentheorbitalplaneandtheearth'sequatorialplane.Mostofthesatellitesoperatinginthisorbitareclosetotheground,withaheightofonlyafewhundredkilometers,sotheyarealsocalledlow-Earthorbits.Chinaislocatedinthenorthernhemisphere.Tosendsatellitesintothisorbit,thecarrierrocketmustbelaunchedinthesoutheastdirection,sothatpartofthespeedoftheearth'srotationfromwesttoeastcanbeused,therebysavingtheenergyoftherocket.Therotationspeedoftheearthcanbecalculatedfromtherotationspeedoftheequator,thelaunchazimuthandthegeographiclatitudeofthelaunchpoint.Itisnotdifficulttoimaginethatlaunchingasatelliteontheequatorinthedirectionofdueeasthasthegreatestspeedavailable,andthehigherthelatitude,thelowerthespeedavailable.

The8scientificandtechnologicaltestsatelliteslaunchedbyChinawiththeLongMarch-1andStorm-1carrierrockets,andthe17satelliteslaunchedwiththeLongMarch-2,No.2CandNo.2DcarrierrocketsreturnedTheremotesensingsatellitesandtheShenzhoutestspacecraftlaunchedbytheLongMarch2Fcarrierrocketalluseprogradeorbit.TheyalltookofffromtheJiuquanLaunchCenterandweresentintolow-Earthorbit.OneBeidounavigationtestsatellitelaunchedbytheLongMarch3Acarrierrocketalsoadoptsaprogradeorbit.

Retrogradeorbit

Thecharacteristicofretrogradeorbitisthattheorbitalinclinationisgreaterthan90degrees.Toputthesatelliteintothisorbit,thelaunchvehicleneedstobelaunchedtowardthesouthwest.Notonlycannotusepartofthespeedoftheearth'srotation,butalsopayextraenergytoovercometheearth'srotation.Therefore,exceptforsun-synchronousorbits,suchorbitsaregenerallynotused.

Becausetheearth'ssurfaceisnotanidealsphericalshape,itsgravitydistributionisalsouneven,whichmakesthesatelliteorbitplaneconstantlychangingintheinertialspace.Specifically,theequatorialpartoftheearthisalittlebulging,whichcreatesadditionalattractiontothesatellite,andaddsamomenttotheorbitalplanetomaketheorbitalplaneslowlyprecess,andtheprecessiondirectionisrelatedtotheorbitalinclination.Whentheorbitalinclinationangleisgreaterthan90degrees,themomentiscounterclockwise,andtheorbitalplaneprecessesfromwesttoeast.Appropriateadjustmentofthesatellite'sorbitalheight,inclinationandshapecanmakethesatellite'sorbitalplane'sprecessionangularvelocitymoveeastwardby0.9856degreeseveryday,whichisexactlyequaltothedailyaverageangularvelocityoftheearthorbitingthesun.Thisisacircularsun-synchronousorbitwithgreatapplicationvalue.Satellitesoperatinginsun-synchronousorbitscanobservesatellitecloudsandgroundtargetsunderthesametimeandilluminationconditions.Applicationsatellitessuchasmeteorology,resources,andreconnaissancemostlyusethistypeoforbit.TwoFengyun-1meteorologicalsatellitesandtwoearthsatellitestomeasureatmosphericdensitylaunchedbyChinawiththeLongMarch-4rocket,oneFengyun-1meteorologicalsatellitelaunchedwiththeLongMarch-4rocket,andoneresourcejointlyproducedbyChinaandBrazilTheNo.1satellite,1ChinaResourcesNo.2satellite,and1PracticeNo.5scientificexperimentsatelliteallusethisorbit.TheyallliftedofffromtheTaiyuanlaunchcenter.WhentheChangsiBrocketlaunchedtheZiyuan-1satellite,italsosentasmallBrazilianscientificapplicationsatelliteintothesun-synchronousorbitbymeansofadouble-arrowsatellite.

Equatorialorbit

Thecharacteristicoftheequatorialorbitisthattheinclinationoftheorbitis0degrees,andthesatellitemovesovertheequator.Therearecountlesssuchorbits,butoneofthegeostationaryorbitshasaspecialimportantposition.Sincethespeedofasatellitevarieswiththeheightfromtheground,thehighertheorbit,thelowerthespeed,andthelongertheorbitingperiod.Therefore,calculationsshowthatwhenittravelsfromwesttoeastonacircularorbitof35,786kilometersabovetheequator,ittravelsfor1week.Thetime,whichhappenstobe23hours,56minutesand4seconds,isthesameasthetimeoftheearth'sonerevolution.Thisorbitiscalledthegeostationaryorbit.Becausethesatellite'sorbitingperiodisequaltotheearth'srotationperiod,andthetwodirectionsarethesame,theyremainrelativelystationarywitheachother.

Fromtheground,thesatelliteseemstobefixedatacertainpointabovetheequator.Thescientificideathatthreecommunicationsatellitescanbedistributedevenlyonthegeostationaryorbittocarryoutglobalcommunicationhasalreadybecomeareality.Theworld'smajorcommunicationsatellitesarealldistributedonthisorbit.Someweathersatellitesandearlywarningsatelliteshavealsobeensentintogeostationaryorbit.Chinahassuccessivelylaunched1testsatellite,5Dongfanghong-2seriescommunicationsatellites,2Fengyun-2meteorologicalsatelliteswiththeLongMarch3rocket,and1PracticalNo.4explorationsatellitewiththeLongMarch3Arocket.TherearetwoDongfanghong-3communicationssatellitesandoneZhongxing22communicationssatellites.Tenofthesesatelliteshaveenteredapredeterminedpositioninthegeostationaryorbit.Tolaunchthistypeofsatellite,theapogeeenginemustbecarriedonthesatellite.Afterthelaunchvehicleputsthesatelliteintoalargeellipticalsynchronoustransferorbit,thegroundwillissueacommandtoignitetheapogeeengineonthesatelliteandmovethesatelliteintoastationaryorbit.

Polarorbit

Asfarasthesatelliteorbittypeisconcerned,thereisalsoapolarorbitwithanorbitalinclinationof90degrees.Itisnamedaftertheorbitalplanepassesthroughthenorthandsouthpolesoftheearth.Satellitesoperatinginthisorbitcanflyoveranyareaontheearth.AlthoughChinahasnotdevelopedsatellitesoperatinginsuchorbits,ithaslaunchedsatellitesinsuchorbits.TheLongMarchIICmodifiedrockettookofffromTaiyuansixtimesintheformofonearrowandtwostars,andsent12U.S.Iridiumstarsintospace,whichbelongedtothislaunchmethod.

Sun-synchronousorbit

Duetotheoblatenessoftheearth(theearthisnotasphericalshape,butisraisedattheequator),thesatelliteorbitplanerotatesaroundtheearth'srotationaxis.Iftherotationdirectionandangularvelocityofthesatelliteorbitplanearoundtheearth'srotationaxisarethesameasthedirectionandaverageangularvelocityoftheearth'srevolutionaroundthesun,thenthiskindofsatelliteorbitiscalledasun-synchronousorbit.Meteorologicalsatellites,resourcesatellitesandotherearthobservationsatellitesusethisorbit.Theadvantageisthatitnotonlyallowsthesatellitetooverlooktheentiresurfaceoftheearth,includingthepolesoftheearth,butalsohasbasiclightingconditionseverytimethesatellitepassesthroughaspecificarea.Nochange,whichisconducivetoobtaininghigh-qualityimagesofgroundtargets.

Someartificialearthsatellitesoperateincircularorbits,andsomeoperateinellipticalorbits:theyalsohavehighandlowpoints:theorbits200～2000kmabovethegroundarecalledloworbits,andtheorbits2000～20000kmabovethegroundarecalledloworbits.Mediumorbit,orbitsabove20000kmfromthegroundarecalledhighorbits.Inordertocompletethescheduledtasks,differentsatelliteshaveobviousdifferencesinorbitshapes,heights,andsoon.

Forexample,theuseofacircularorbithastheadvantageofkeepingthesamedistancefromthesurfaceoftheearth,sosatellitesusedforobservingtheearth,communicationsandbroadcasting,navigationandpositioning,andgeodeticsurveysoftenusethistypeoforbit;however,somesatellitesalsousethistypeoforbit.Ellipticalorbits.Forexample,Russia’s"Lightning"communicationssatellitesoperateinlargeellipticalorbits.ThisisbecauseRussiahasarelativelyhighlatitude.Ifgeostationaryorbitsatellitesareused,theycannotcoverhighlatitudes.Theapogeeheightofthe"Lightning"communicationssatelliteorbitis40000km,theperigeeis470km,theinclinationangleis63°,thatis,theapogeeisoverthenorthernhemisphere.Inthisway,thesatellitecanslowlypassthroughtheterritoryofRussia,andthetimetolosecontactwiththegroundcontrolstationisveryshort.However,inordertoensureuninterruptedcommunicationwithinRussia,multiple"Lightning"satellitesarerequiredtocooperate.Inaddition,ifitisforscientificresearch(tostudytheintensityofthemagneticfieldatdifferentheightsoftheearth,atmosphericpressure,temperature,density,andtheintensitydistributionofcosmicspaceradiation),tomakethedetectionrangelarger,youcanchooseaflatorbit.ThePractice-1scientificsatellitelaunchedbymycountryonMarch3,1971hasanorbitalperigeeof266kmandapogeeofl826km.

Useclassification

Orbittype

GeostationaryOrbit(GEO:GeostationaryOrbit)

High-orbitsatellite,about36,000kilometersfromthesurfaceHighaltitude,andorbitingtheearthontheequator,alsoknownasasynchronousorbitsatellite

PolarOrbitSynchronousnearRecurrentOrbit

Orbitheight

h3>

High-orbitsatellites(alsoknownasgeostationaryorbitsatellites):GeostationaryOrbit(Geo:GeostationaryOrbit)

High-orbitsatellitesareabout36,000kilometersabovetheearth’ssurfaceandorbittheearthontheequator.Alsoknownasgeostationaryorbitsatellitesorgeostationarysatellites

Medium-EarthOrbit(MEO:Medium-EarthOrbit)

Low-orbitsatellites(alsoknownascircumpolarsatellites):Low-EarthOrbit(LEO:Low-EarthOrbit)

Satelliteweight

Largesatellite(greaterthan3000kg)>3tons

Mediumsatellite(lessthan3000kg)<3tons

Smallsatellites(lessthan1000kg)<1ton

Minisatellites(150kg)

Microsatellites(50kg)

Satellitefunction

Commercialcommunicationsatellite

Scientificsatellite

Militarysatellite

Satelliteclassification

PressUsageclassification:

Canbedividedintobroadcastingsatellites,communicationsatellites,meteorologicalsatellites,earthobservationsatellites,navigationsatellites,astronomysatellites,reconnaissancesatellites,spacesatellites,tow-freesatellites,scienceandtechnologysatellites,earlywarningsatellites,Satellitesatelliteandsoon.

Broadcastsatellites:artificialsatellitesspeciallydesignedandmanufacturedforsatelliteTV.

Communicationsatellites:Communicationsatellitesarecurrentlythemostcloselyrelatedartificialsatellitestoeveryone’slives.Forexample,televisionbroadcasts,personalmobilephones,andhigh-speednetworksandcommunications-relatedservicesareinseparablefromcommunicationssatellites.

Meteorologicalsatellites:Inancienttimes,peoplecouldonlyguessatthechangeableclimatebasedonexperience.Theemergenceofmeteorologicalsatelliteshasenabledpeopletograspclimatechangewithinafewdays.Meteorologicalsatellitesobservetheearthfromdistantspace,notonlycanobservethechangesofweatherinlargeareas,butalsoobservethechangesofweatherinsmallareasisalsohisroutinetask.Generally,whenwearewatchingtheweatherforecastofnews,thesatellitecloudpicturebehindtheanchoristheobservationresultoftheweathersatellite.Thetyphoonforecastisevenmorefamiliartoeveryone.Inadditiontoobservingtheearth’sweatherandclimate,meteorologicalsatellitescanalsomonitortheso-calledspaceweather.Stormsonthesurfaceofthesunareofthistype.Suchincidentsoftencausedamagetomanyelectricalobjectsontheearth.Meteorologicalsatellitesalsohaveotherfunctions.Itcanprovidemonitoringinformationfornaturaldisasterssuchasfloodsandforestfires,anditcanalsoprovidecertaininformationonresourcessuchasfishinggroundsorlandresources.Inthisway,thedevelopmentofvariousnaturalresourcesandthereliefofnaturaldisasterscanachievetwicetheresultwithhalftheeffort.

Earthobservationsatellites:ThesesatellitesallowscientiststogathervaluabledataabouttheEarth’secosystem.

Navigationsatellites:Atthebeginning,navigationsatellitesweredesignedformilitaryuse,andthenduetotheardentdemandfromthecivilianpopulation,themilitaryonlyreleasedthistechnology.OneofthemostfamousandwidelyusedistheglobalsatellitepositioningsystemoriginallyusedbytheUSmilitary,whichisreferredtoasGPSforshort.Theuseofglobalsatellitesystemsmakeshumantrafficsaferandmoreefficient.Especiallyforshipssailingintheboundlessseaorairplanesinthevastsky,withtheglobalsatellitepositioningsystem,theywillnotlosetheirway,andcancontrolthechannelonthemostefficientroute.Therefore,inadditiontoincreasingsafety,itcanfurtherreduceshippingcosts.Atthesametime,notonlyseaandairtransportation,butalsorailwaytransportationcanimprovetransportationefficiency.Duetothedevelopmentofelectronictechnology,GPSreceivershavebecomesmallerandsmaller.Someadvancedcarmanufacturershaveinstalledthissetofequipmentonpersonalvehicles.Itsfunctionnotonlycanbeusedonthemap,butalsocanbeguidedtothenearestroutebytheservicestationontheground,andevenavoidthetroubleoftrafficjams.Untiltoday,mostoftheglobalsatellitepositioningsystemsarecomplementarytoothertypesofsatellites,sothattheaforementionedvarioussatelliteshavemoreaccuratepositioningcapabilitiesandgreatlyimprovetheavailabilityofdata.

Classifiedbyheight:

Artificialearthsatellitesplayanirreplaceableroleinallaspectsofhumanproductionandlife.Therearemanytypesofartificialearthsatellites,differentpurposes,anddifferentorbitalheights.Accordingtotheirdifferentorbitalheights,satellitescanbedividedinto:①low-orbitsatellites-orbitalheightslessthan5km;②mediumandhigh-orbitsatellites-orbitalheights5～20km;③High-orbitsatellites-theorbitheightisabove20km.NASA'sphotographsoftheexistingartificialearthsatellitesinspace.Theearthislikeahoneycomb,surroundedbysatellites.Exceptforgeosynchronousorbitingsatellites,mostofthesatellitesareveryclosetotheearth'ssurface.Theheightofthegeosynchronousorbitsatellitefromtheearthisabout36000km,whichisabout5.7earthradius.

Flightmode

Returnablesatellite

Non-returnablesatellite(ortransmissionsatellite)

Famousartificialsatellite(pressLaunchtimearrangement)

SovietSputnik1(October4,1957)

UnitedStatesGeostationaryCommunicationsSatellite1(1963),No.2(1963)and3(1964)

ChinaDongfanghongOne(1970)

CanadianBrother1(1972)

HermesCommunicationSatellite(1976))

KeoSatellite-ASpaceTimeCapsule(2006)

SatelliteService

SatellitePhone

SatelliteInternet

SatelliteTV

EngineeringSystem

Thegeneralsystemhasstructure,temperaturecontrol,attitudecontrol,energy,tracking,telemetry,remotecontrol,communication,orbitcontrol,antennaandothersystems,Thereturnablesatellitealsohasarecoverysystem,inadditiontovariousspecialsystemssetupaccordingtotheneedsofthemission.Theartificialsatellitecansuccessfullyperformthescheduledmission,thesatelliteitselfisnotenough,butacompletesatelliteengineeringsystemisrequired,whichgenerallyconsistsofthefollowingsystems:

1,launchsitesystem

2.Launchvehiclesystem

3.Satellitesystem

4.Measurementandcontrolsystem

5.SatelliteApplicationSystem

6.Recoveryareasystem(limitedtoreturnablesatellites)

Components

Inthesatellitesystem,variousdevicesaredividedintotwoparts:payloadandsatelliteplatformaccordingtotheirfunctions.Thesatelliteplatformisdividedintomultiplesubsystems:payload(differenttypesofsatellitesaredifferent,thecommononesare:)

1.Groundcamera

2.Stellarcamera

3.Carryingpayload

Satelliteplatform(providingenvironmentandtechnicalconditionsfortheoperationofpayload,including:)

1.Servicesystem

2.Thermalcontrolsubsystem

3.Attitudeandorbitcontrolsubsystem

4.Programcontrolsubsystem

5.Telemetrysubsystem

6.Remotecontrolsubsystem

7.Trackingandtestingsubsystem

8.Powersupplyanddistributionsystem

9.Returnsub-system(limitedtoreturnablesatellites)

Gravityissues

Fromtheearthreferencesystem,undernormalcircumstances,thedirectionofgravityonearthsatelliteschangesconstantlyanddoesnotpointtotheground.Whenthesatellitemovesclosetotheground,theinertialcentrifugalforceandCoriolisforceitreceivesaremuchsmallerthanthegravityoftheearth.Thegravityisapproximatelyequaltothegravityoftheearth,andthemovementofthesatelliteissimilartoauniformcircularmotion.Thefartherthesatelliteisfromtheground,thegreaterthedifferencebetweenthegravityandtheearth'sgravity,andthetwocannotbeequal.Onlytheequatorialorbitingsatellitemakesauniformcircularmotionaroundtheearth(buttheorbitingspeedisdifferentfromthatseenontheearth-starsystem),andthecentripetalforceisprovidedbythegravityofacertainmagnitude(butnotequaltothegravityoftheearth)alwayspointingtothecenteroftheearth.Thegravityonageostationarysatelliteiszero,anditisamorespecialcasewhenitisstationaryintheairrelativetotheearth.

Theworld’smost

Thesuccessfullaunchofthefirstman-madeearthsatelliteoftheformerSovietUnionopenedthepreludetothemarchofmankindintospaceandgreatlystimulatedtheenthusiasmofallcountriesintheworldtodevelopandlaunchsatellites.ThemainmissionofthefirstartificialearthsatellitelaunchedbytheformerSovietUnionwasnotscientificinvestigation,butpoliticalpropaganda.Thefirstsatellitetotheskyisthemostdramaticscientificeventinhistory.

Themulti-stagerocketofthefirstartificialearthsatellitelaunchedbytheformerSovietUnionreachedanaltitudeofmorethan900kilometers,andthenflewparalleltotheearthataspeedofabout28,800kilometersperhour.Finally,thesatellitebrokeawayandstoppedburning.Thefirst-stagerocketestablishesitsownorbitabout880kilometersabovetheearth.Theartificialsatelliteorbitstheearthevery96.2minutes.Duetotherotationoftheearth,artificialsatellitescanflyoverallcontinentsandallinhabitedareas.TheUnitedStatessuccessfullylaunchedthefirstsatellite"Explorer"-1onJanuary31,1958.Thestarweighs8.22kg,hasacylindricalconewithaheightof203.2cmandadiameterof15.2cm.Itorbitstheearthinanellipticalorbitof360.4kilometersperigeeand2531kilometersapogee,withanorbitalinclinationof33.34"andanoperatingperiodof114.8minutes.Launch"Explorer"-ThelaunchvehicleofNo.1isthe"Juppet"℃four-stagelaunchvehicle.

Francesuccessfullylaunchedthefirst"testsatellite"-1(Al)artificialsatelliteonNovember26,1965.Satellite.Thesatelliteweighsabout42kilogramsandhasanoperatingperiodof108.61minutes.Ittravelsinanellipticalorbitof526.24kilometersatperigeeand1808.85kilometersatapogee,withanorbitalinclinationof34.24".ThelaunchvehicleforlaunchingtheA1satelliteisthe"Diamond,tAthree-stagerocket,withatotallengthof18.7meters,adiameterof1.4meters,andatake-offweightofabout18tons.

JapansuccessfullylaunchedonFebruary11,1970Thefirstman-madesatellite"Osumi"wasbuilt.Thesatelliteweighsabout9.4kg,hasanorbitalinclinationof31.07",aperigeeof339kilometers,anapogeeof5138kilometers,andanoperatingperiodof144.2minutes.Thecarrierrocketforlaunchingthe"Osumi"satelliteisthe"Landa"-45four-stagesolidrocket.Therockethasatotallengthof16.5meters,adiameterof0.74meters,andatake-offweightof9.4tons.Thefirststageconsistsofthemainengineandtwoboosters,withthrustsof37tonsand26tons,respectively;thesecondstagethrustis11.8tons;thethirdandfourthstagethrustsare6.5tonsand1tonrespectively.

ChinasuccessfullylauncheditsfirstartificialsatelliteonApril24,1970.Onthesameday,theDongfanghong1satellitetookofffromtheJiuquanSatelliteLaunchCentercarriedbytheLongMarch1carrierrocketandenteredthescheduledorbit.ThisachievementmarksthatChinahasbecomethefifthcountryintheworldthatcandevelopandlaunchartificialsatellitesonitsown,aftertheSovietUnion,theUnitedStates,France,andJapan.Thestarisabout1meterindiameterandweighs173kilograms.Itorbitstheearthinanellipticalorbitof439kilometersperigeeand2384kilometersapogee,withanorbitalinclinationof68,5",andanoperatingperiodof114minutes.Thelong-rangerocketforlaunchingthe"Dongfanghong"1satelliteItisthe"LongMarch"No.1three-stagecarrierrocket.Therockethasatotallengthof29,45meters,adiameterof2.25meters,atake-offweightof81.6tons,andalaunchthrustof112tons.

TheBritishsuccessfullysucceededonOctober28,1971.Launchedthefirstartificialsatellite"Prosparo"attheWoomerarocketlaunchsiteinAustralia.ThelaunchvehicleistheBritishBlackArrowlaunchvehicle.Theperigeeis537kilometersandtheapogeeis1593kilometers.ThestarWeighing66kilograms(145pounds),themaintaskistotestvarioustechnologicalinnovations,suchastestinganewtelemetrysystemandsolarbatterypack.ItalsocarriesamicrometeordetectortomeasurethiskindofcosmicdustintheupperatmosphereoftheearthThedensityofhigh-speedparticles.

Inadditiontotheabove-mentionedcountries,Canada,Italy,Australia,Germany,theNetherlands,Spain,IndiaandIndonesiaarealsopreparingtolaunchtheirownsatellitesorhavecommissionedothercountriestolaunchartificialsatellites.

OnOctober4,1957,theSovietUnionlaunchedthefirstartificialearthsatellite.Thiseventwasofepoch-makingsignificance,anditannouncedthatmankindhadenteredthespaceage.Thefirstartificialearthsatellitewassphericalwithadiameterof58cm.Itweighs83.6kilograms.Itfliesinanellipticalorbitandcirclestheearthevery96minutes.Theman-madeearthsatellitecarriesaradiotransmitter,whichkeepssendingout"di-di-di"signalstotheearth.SomepeopleSurroundedbytheradio.Helistenedtothefirstsoundfromspace.Otherslookedupattheskyandtriedtosearchforthebrighttrajectoriesofartificialearthsatellitesatnightwiththeirnakedeyes.However,fewpeopleknewthatartificialearthsatellitesweremannedspacecraft.Foreword,scientistsaresteppinguppreparationsformannedspaceflight.

Onemonthlater,onNovember3,1957,theSovietUnionlaunchedasecondman-madeearthsatellite.Itsweightincreasedbymorethan5times.Itreaches508kilograms.Thissatellitehasaconeshape.Inordertosavespaceonthesatellitetoaddasealedbiologicalcabin,manymeasuringinstrumentshavetobemovedtothelastrocket.Acylindricalcabinliespeacefully.Apuppynamed"Lykayi".Thepuppyisconnectedtomedicalinstrumentsthatmeasurepulse,respiration,andbloodpressure,andreportsthesedatatothegroundatanytimeviaradio.Inordertokeeptheairinthecabinfreshandclean,airregenerationisalsoinstalledDeviceandexcretiondeviceforprocessingfeces.Thecabinmaintainsacertaintemperatureandhumiditytomakethepuppyfeelcomfortable.Inaddition,thereisaself-feedingdevicethatlightsupthesignallightthreetimesadaytonotifyLeicatohaveameal.Regrettably,Duetothelimitationofthetechnicallevelatthattime,thesatellitecouldnotberecovered.Thetestdoglivedinthesatellitebiologicalcabinforaweek.Aftercompletingalltheexperimentaltasks,ithadtotakepoisontocommitsuicideandbecamethefirstvictiminthespaceflight.

Launchcountry

Bytheendofthe20thcentury,onlyafewcountriesintheworldhaveenteredthespaceclub-withindependentsatellitelaunchcapabilities.Thesecountriesandregionsinclude(asofFebruary2007):CIScountries/formerSovietUnion,theUnitedStates,France,Japan,China,theUnitedKingdom,IndiaandIsrael.ThelaunchesbyIraqandNorthKoreawerenotrecognized.Brazilconductedthreelaunchattemptsin1997,1999and2003,butnoneofthemweresuccessful.Tothisday,therearestillafewcountriesstilltryingtoentertheaerospaceclub.Intheearlydays,bothItalyandKazakhstanhadthetechnicalconditionsforrocketandsatelliteresearchanddevelopment,andbothhadrocketlaunchsites(SanMarcoItalianOffshorePlatformandBaikonurLaunchSite,whichweremainlyresponsibleforlaunchingmissionsfortheUnitedStatesandRussia).Ukrainehasrocketmanufacturingcapabilitiesbutdoesnothaveconditionssuchaslaunchsites.CompaniessuchasthemultinationalEuropeanSpaceAgencyESAandprivately-ownedmaritimelaunchcompaniesarealsoconsideredmembersoftheAerospaceClub.

OnOctober4,1957,theworld’sfirstartificialearthsatellitewasmadeandsuccessfullylaunchedbytheSovietUnion.Therocketthattransportsthesatelliteenablesthesatellitetoobtainthenecessaryorbitalspeedofabout8,000meterspersecond.Accordingtocalculations,thissatelliteisoperatingatanaltitudeof900kilometersabovetheground;ittakes1hourand35minutestomakeafullrevolution,andtheinclinationangleformedbetweenitsorbitandtheequatorialplaneis65degrees.

Theartificialsatelliteisasphericalbodywithadiameterof58cmandaweightof83.6kg.Itisequippedwithtworadiotransmittersthatcontinuouslyemitradiosignals.Thefrequenciesare20.005and40.002MHz(wavelengthsareabout15and7.5meters,respectively).Thesignalisintheformofatelegraphsignal,andeachsignallastsforabout0.3seconds.Theresttimeisthesame.

Asearlyastheendofthe19thcentury,Tsiolkovsky,anoutstandingRussianscientist,hadscientificallydemonstratedthepossibilityofusingrocketstoachievespaceflightforthefirsttimeinhiswork.