第一章航天器通信概述

DevelopmentandApplicationofSpacecraftCommunication（航天器通信的發(fā)展和應(yīng)用）LLIUXLiuXinReferenceBooks2王建萍，劉濤，鄧忠禮，鄭雪峰

著

周賢偉

編叢書(shū)名：現(xiàn)代通信高技術(shù)叢書(shū)----深空通信國(guó)防工業(yè)出版社Overview（緒論）3SpacecraftsandCommunications4Whenthespacecraftroams(漫游)intheexpansive(浩瀚)space,thestaffonthegroundwillneedtogetintouchwiththespacecrafttimelyandeffectively,inthiscase,thespacecraft‘scommunicationsystemwillplayahugerole(發(fā)揮巨大作用).Byspacecraftcommunicationsystem,peoplecanlearntheintuitive(直觀)flightconditions,andformannedspacecraft,agoodcommunicationsystemcandisplaythedetailedstatusoftheastronauts（宇航員）inthespacetothegroundstaff.5ClockonthespacecraftAfterthespacecraftgoesintoorbit（軌道）,thegroundmonitoringstations(地面監(jiān)測(cè)站)willalwaysobservethespacecraft'sactivities.Forthesatellitesandthemannedspacecraft,theaccuracyofthetimeisparticularlyimportant,whichrelateswiththereturnofthespacecraft,andevenaffectsthelivesoftheastronauts（宇航員）.Therefore,itisveryimportantthattheclocksonthegroundandthespacecraftbecomesextremelyaccurateandconsistent（一致）.6AccordingtotheEinstein’srelativitytheory（愛(ài)因斯坦相對(duì)論）,theclockinaweakgravitationalfield(弱重力場(chǎng))goesfasterthanthatinthestronggravitationalfield;inthevicinity（附近）oftheEarth'ssurface,theclockfrequencywillincreasesomebyincreasingonemeter,however,thiseffectisnotobvious.Thefrequencyoftheclockontheearthwilldecreasesomebytheaffectionoftheearth’sorbitmovementaroundthesunandthesun‘sgravity（引力）;iftheclockisveryfarfromtheground,theacceleration（加速）effectofthetimeismoreobvious.Thus,itisinevitable（不可避免）thattheclockonthespacecraftmovinginthespaceorbitrunsfasterrelatively.7Clockonthespacecraft8

WorldTimeTheworldtimingmethodwasproposedbefore1960.DuetotheEarth’srotation（旋轉(zhuǎn)）,thesunwillgooveraplaceoftheearthperiodically,andtheaveragetimeintervalthatthesunpassesthroughthemeridian（子午線）twiceiscalledameansolarday（平均太陽(yáng)日）.thetimereferencingthemeansolardayiscalledthemeansolartime;themeansolartimestartingfromtheBritainGreenwichMeridian（格林威治子午線）iscalledtheworldtime.9Atomictime（原子時(shí)）StartfromZeroo’clockoftheworldtimein1thJanuary1958.Asthefrequencyoftheelectromagneticwave（電磁波）emitted（發(fā)射）andabsorbedbythechangedatomisextremelystable（穩(wěn)定）,theatomictimingismoreuniformthanthetimingsystembasedontheEarthrotation,thereforetheatomicclockiswidelyusedinthespacecraftcommunications.10Inordertomaketherunningvelocities（速度）oftheclocksonthespacecraftandtheterrene（陸地）tobeconsistent,thescientistsslowtherunningvelocityoftheclockonthespacecraft,inthiscase,thetimedisplayedbytheclockonthespacecraftisthesameasthatdisplayedbytheclockontheterrene,whichgivesaverybighelptothesatellitecommunicationandpositioning.Receptionandtransmissionoftimecommandbythespacecraft11SpacecraftCommunicationsSpacecraftcommunicationsystemreferstoacquireandtransmitthevisual,dataandaudio（視頻音頻）informationbetweenthespacecraftandtheterreneincludingtheenvironmentalimagesinsideandoutsidethemannedspacecraftcabin（載人飛船倉(cāng)）thelivingimagesoftheastronautsthevoicebetweentheastronautsandthestaffschargingthegroundstationthedatainformationordatacommandbetweenthespacecraftandtheterrene.Voicecommunicationisabasicrequirementofthemannedspacecraft.Voicecommunicationsestablishthemutual（相互）contactbetweentheterrestrial-communicationstaffsandtheastronauts,andsometimesitcanbeconverted（轉(zhuǎn)接）directlytotheflightcontrolcenter.Byvoicecommunications,thecontrolcentercanreceivetheastronauts’currentsituationstimely,andsendthemactiveinstructions（活動(dòng)指令）tocompletethespaceflightmissions.1213Informationreceptionandtransmissionontheterrene14Theearlyspacecraftssuchasthe“Oriental”（東方號(hào)）spacecraftoftheformerSovietUnion（前蘇聯(lián)）andtheAmerica‘s“Gemini（雙子座）”spaceship,transfertheimagesusingtheanalogsignals(模擬信號(hào)).Althoughthetransfertechniqueoftheanalogimageisverysimple,thetransferqualityoftheimageisnotgood.Withthedevelopmentofthespacetechnology,theimage’squalityrequirementsareincreasing,andcurrentlymostofthemannedspacecraftstransmitthedigitalimage(數(shù)字圖像),whichhashigherqualityandcanbetransmittedbysharingthechannelwithotherspacecraftcommunications.15Throughtransmittingthetelevisionimagesfromthespacecrafttotheground,theastronauts’statecanbedirectlymonitoredbythegroundstations.Whentherendezvous（交匯）anddocking（對(duì)接）isimplemented,theTVimagescanmaketheastronautsandthegroundstationstointuitively（直觀）understandtherelativemotionbetweenthespacecraftandthetarget,inordertocontrolthespacecrafteffectively.TVcanalsobeusedforpublicity（宣傳）,unexpectedeventmonitoringandflightliteraturecompilation（飛行文獻(xiàn)的編集）etc.16InformationTransmissionandreceptionofthespacecraft17SpacecraftPowerTomakethespacecraftexplore(探索)thespace,thegreatpowerisneeded,thereforethescientistsattach（綁縛）avarietyofpowerequipmentsonthespacecraftforitsnormalwork.Therocketengine（火箭發(fā)動(dòng)機(jī)）isthesolepowersourcetosendthespacecraftintothespace,andafterenteringthespace,thespacecraftwilluseitsowncarryingfuel（攜帶燃料）topushitselftothetarget.Somespacecraftsalsohavesmallrocketenginesonthem,andmaycarrysomefuel.However,therocketengineonthesatellitehavetobeusedrepeatedly,sothatthesatellitecanchangesitsorbitslowly.18Theenergyclassificationusedbythespacecraftpropulsion（推進(jìn)）includeschemicalpower,airpower,electricpower,solarsailpower（太陽(yáng)帆動(dòng)力）,nuclearpower（核動(dòng)力）andlaserpower（激光動(dòng)力）.Thepropulsionsusedinthemannedspacecraftarebasicallythechemicalrocketengines,mostofwhichareliquid（液態(tài)）rocketengines.Thesolid（固態(tài)）engineisonlyusedinthesituationforstartingonce,forexample,theescapinglife-saving（逃逸求生）engineandthebrake（制動(dòng)）engine.19Liquidhydrogen-fueledrocketengine液氫燃料發(fā)動(dòng)機(jī)Ionengine離子發(fā)動(dòng)機(jī)20Thepropulsionsystemofthe“Union（聯(lián)盟）”TMspacecrafthasatotalof35rocketengines,including1brakeengine,14bigattitudecontrol(大姿態(tài)控制)engines,12smallattitudecontrolengines,and8returning-capsule(返回艙)attitudecontrolengine.The“Apollo（阿婆羅）”spacecraftisequippedwith50engines,andsevenpropulsionsubsystemsincludingthelaunchescape(發(fā)射救生)system,theservicepropulsion(服務(wù)推進(jìn))system,thedecliningpropulsion(傾斜推進(jìn))system,therisingpropulsion（上升推進(jìn)）system,theserving-capsulereactedcontrol（服務(wù)艙反作用控制系統(tǒng)）system,thelunar-capsulereactedcontrolsystems（登月艙反作用控制系統(tǒng)）andcommanding-capsulereactedcontrolsystem（指揮艙反作用控制系統(tǒng)）21"Viking"5Crocketengine22Thespacecraftdoesn’tonlysendthepayload（載荷）ontotheEarthorbitorbacktotheEarth,butalsostaysontheorbit,takingadvantageofavarietyoftestinginstrumentsandequipmentstocarryoutvariousexperimentsandstudies.Toaccomplishthesetasks,thespacecraftdoestheentering-orbitflight（入軌飛行）,andperformsorbitalmaneuvers(軌道機(jī)動(dòng)),aswellaschangesandmaintainsacertainflightattitudewiththepropulsionsystem.Thus,thespacecraftrequiresthreekindsofpropulsiondevices,thatisthemainengine,themaneuvering(機(jī)動(dòng))engineandtheattitudecontrolengine.23Enginesonthespacecraft24ReturntotheEarthSomespacecraftsdon’tonlybeartheburdenofexploringthemysterious（神秘）space,butalsoreturntotheearthaftercompletingthespacemissions.Sincethespeedofthespacecraftisveryhigh,howtoensurethesafereturningandlandingofthespacecraftisveryimportant.25Stepone:orbitalchange（軌道改變）BeforereturningtotheEarth,thespacecraftautomaticallyadjusts（調(diào)整）thespaceorbitattitudetothereturningattitudeaccurately,andaftertheadjustment,thespacecraftmaintainsastablerunninginthisattitude.Thenbystartingthebrakerocketengineandgeneratingareversepushforce(反相推力),therunningspeedofthespacecraftisreduced,andthespacecraftisforcedtobeawayfromtheoriginalorbitandenterthepresetreturningorbit(預(yù)先返回軌道).26Steptwo:throughtheblackarea黑障區(qū)Whenthespacecraftgoesdowntotheheightofabout40kilometersawayfromtheground,thegas（氣體）andthespacecraft’ssurfacematerialintheseveral-thousand-degreehigh-temperatureareaformedaroundthespacecraft’ssurface,aredecomposed（分解）andionized（電離）intoalargenumberofmolecules（分子）.Thesemoleculesformaplasmasheath（等離子鞘）outsidethespacecraft.Theplasmasheathcanabsorbandreflecttheelectromagneticwaves,andmaketheradiocommunicationsbetweenthespacecraftandtheoutsideworldinterrupted（中斷）.Thisphenomenonbecomestheblackbarrier,andtheareayieldingtheblackbarrieriscalledtheblackbarrierarea.27Step3:SoftlandingThespacecraft’ssoftlandingisthatthespacecraftlandedsafelybythedeceleration（減速）meanssuchasbrakerocketandparachute(降落傘).Toensurethespacecraft’ssafereturntotheground,itisnecessarytodevelopareliableparachutesystemthatallowsthespacecrafttolandatlowspeedbyparachutedecelerationinlowaltitudeclosetotheground,sothatthespacecraftcanbeensuredtoreturntothegroundintactly(完好).28PositioningandSearchingIftheabovekeytechnologiesaresuccessfullyresolved,thespacecraftwillbeabletoreturnsafelytotheground.Butonthevast（遼闊）andcomplexland,wheretofindthespacecraftbackfromthespace?Thisrequiresthatthepositionofthelandingspacecraftcanbeforecasted（預(yù)測(cè)）andmeasuredtimelyandaccurately,andthestaffintherecoveryarea（回收區(qū)）canfindthelandingspacecraftassoonaspossible.29303132ImportanceofpositioningandcommunicationwhenlandingWhentheRussia“Union”TMAlmannedspacecraftreturntothelandonMay4,2003,itdeviates（偏離）460kmfromapredeterminedlandingsite,andoncelosesthecontactwiththegroundcontrolcenterinMoscowforuptotwohours.Fortunately,thethreeastronautsonthespacecraftaresafe.Thisisthefirstmannedspacecraftreturningfromthespace,sincethewreck（失事）oftheUnitedStates“Columbia（哥倫比亞）”spaceshuttle（航天飛機(jī)）inFebruary2003.

33LandingfieldselectionAtfirstglance,thelandingfieldhasnodifferencefromthegeneralgrassland（草原）andsea,whichseemstobechosenveryrandomly.Infact,itisnotthecase,andtheseplacesareselectedbyconsideringvariousfactorscomprehensively,whichmustbethesafeandeasylandingplaces.Theprincipleofthelandingsiteselectionistofacilitatetheintegrateduseofthecountry‘sspacetracking（航天跟蹤）andcommunicationsnetwork.Thelandingfieldmustbelargeenoughtoaccommodatealargerlandingdeviation（落點(diǎn)偏差）.Theclimaticconditionsofthelandingfieldmustbeverygood,whichcannothavestrongwindsorthunderstorms（雷暴）.Accordingtothecountry’sgeographical（地理）characteristicsandconditions,thelandingfashionsuchaslandlandingorsealanding,shouldbechosen.34Thelandingfieldsofthemannedspacecraftgenerallyhavetwokinds:mainlandingfieldanddeputylandingfield（副著陸）.Inthecaseofthebadweatherconditionsinthemainlandingsite,thedeputylandingfieldcanplayarole.Inaddition,thereareemergencylandingfields（緊急著陸）foremergencyuse,andtheseemergencylandingfieldsshouldchoosesomeregionsaroundtheworld.Thelandingfieldsshouldhavenotonlythefunctionsofthesatellitelandingfields,butalsothefunctionofcommunicatingwiththeastronautsinsidethespacecraft,aswellasthefunctionofrescuingandfetching（救援和接回）theastronauts.35Groundradarvehicleissearchingforspacecraft36"Discovery"spaceshuttleislanding通信技術(shù)

信息的具體形式：聲音、圖像、文字、數(shù)據(jù)等。消息（NEWS，MESSAGE）：——關(guān)于人或事物情況的報(bào)道?！ㄐ胚^(guò)程中傳輸?shù)木唧w對(duì)象：文字，語(yǔ)音，圖象，數(shù)據(jù)等。信息（INFORMATION）：——有用的消息信號(hào)（SIGNAL）：——信息的具體存載體。信息技術(shù)的處理對(duì)象：信息經(jīng)過(guò)傳感器轉(zhuǎn)換為電信號(hào)，就成為信息技術(shù)要處理的對(duì)象。信息技術(shù)概括起來(lái)主要包括兩類技術(shù)，即信息處理和信息傳輸。通信系統(tǒng)

自古以來(lái)，信息就如同物質(zhì)和能量一樣，是人類賴以生存和發(fā)展的基礎(chǔ)資源之一。人類通信的歷史可以追溯到遠(yuǎn)古時(shí)代，文字、信標(biāo)、烽火及驛站等作為主要的通信方式，曾經(jīng)延續(xù)了幾千年。

烽火導(dǎo)航通信（communication）：一切將信息從發(fā)送者傳送到接收者的過(guò)程都是通信過(guò)程。通信系統(tǒng)的主要任務(wù)是傳遞信息。通信系統(tǒng)實(shí)現(xiàn)信息傳送過(guò)程的系統(tǒng)。無(wú)線通信系統(tǒng)

通信也叫信息傳遞，它的主要任務(wù)是傳遞信息，即將經(jīng)過(guò)處理的信息從一個(gè)地方傳遞到另一個(gè)地方。對(duì)信息傳遞的要求主要是提高其可靠性和有效性。信息處理的目的是為了更可靠、更有效地傳遞信息。電通信的發(fā)展歷史從1837年美國(guó)人莫爾斯發(fā)明人工電報(bào)裝置開(kāi)始，至今不過(guò)170年。翻開(kāi)厚厚的電信史冊(cè)，沿著歷史的腳步一路走來(lái)，在技術(shù)和市場(chǎng)需求的雙重驅(qū)動(dòng)下，僅有一百多年歷史的電通信發(fā)生了翻天覆地的巨變，取得了令人驚嘆的輝煌成就。模擬通信系統(tǒng)模型和數(shù)字通信系統(tǒng)模型模擬信號(hào)和數(shù)字信號(hào)模擬信號(hào)：代表消息的信號(hào)參量取值連續(xù)，例如麥克風(fēng)輸出電壓：(a)話音信號(hào)(b)抽樣信號(hào)模擬信號(hào)數(shù)字信號(hào)：代表消息的信號(hào)參量取值為有限個(gè)，例如電報(bào)信號(hào)、計(jì)算機(jī)輸入輸出信號(hào)：通常，按照信道中傳輸?shù)氖悄M信號(hào)還是數(shù)字信號(hào)，相應(yīng)地把通信系統(tǒng)分為模擬通信系統(tǒng)和數(shù)字通信系統(tǒng)。(a)二進(jìn)制信號(hào)(b)2PSK信號(hào)

數(shù)字信號(hào)

數(shù)字通信的特點(diǎn)優(yōu)點(diǎn)抗干擾能力強(qiáng)，且噪聲不積累傳輸差錯(cuò)可控便于處理、變換、存儲(chǔ)便于將來(lái)自不同信源的信號(hào)綜合到一起傳輸易于集成，使通信設(shè)備微型化，重量輕易于加密處理，且保密性好缺點(diǎn)：需要較大的傳輸帶寬對(duì)同步要求高

通信系統(tǒng)主要性能指標(biāo)通信系統(tǒng)的主要性能指標(biāo)：有效性和可靠性有效性：指?jìng)鬏斠欢ㄐ畔⒘繒r(shí)所占用的信道資源（頻帶寬度和時(shí)間間隔），或者說(shuō)是傳輸?shù)摹八俣取眴?wèn)題。可靠性：指接收信息的準(zhǔn)確程度，也就是傳輸?shù)摹百|(zhì)量”問(wèn)題。模擬通信系統(tǒng)：有效性：可用有效傳輸頻帶來(lái)度量。可靠性：可用接收端最終輸出信噪比來(lái)度量。數(shù)字通信系統(tǒng)有效性：用傳輸速率和頻帶利用率來(lái)衡量。碼元傳輸速率RB：定義為單位時(shí)間（每秒）傳送碼元的數(shù)目，單位為波特（Baud），簡(jiǎn)記為B。 式中T－碼元的持續(xù)時(shí)間（秒）信息傳輸速率Rb：定義為單位時(shí)間內(nèi)傳遞的平均信息量或比特?cái)?shù)，單位為比特/秒，簡(jiǎn)記為b/s

，或bps碼元速率和信息速率的關(guān)系 或

對(duì)于二進(jìn)制數(shù)字信號(hào)：M=2，碼元速率和信息速率在數(shù)量上相等。對(duì)于多進(jìn)制，例如在八進(jìn)制（M=8）中，若碼元速率為1200B，則信息速率為3600b/s。頻帶利用率：定義為單位帶寬（1赫茲）內(nèi)的傳輸速率，即 或可靠性：常用誤碼率和誤信率表示。誤碼率誤信率，又稱誤比特率 在二進(jìn)制中有

噪聲是通信領(lǐng)域中出現(xiàn)頻率很高的一個(gè)詞，但通信領(lǐng)域中所謂的噪聲不同于我們所熟悉的以音響形式反映出來(lái)的各種噪聲（如風(fēng)聲、雨聲、人們的吵鬧聲、機(jī)器轟鳴聲等等）。

噪聲其實(shí)是一種不攜帶有用信息的電信號(hào)，是對(duì)有用信號(hào)以外的一切信號(hào)的統(tǒng)稱。概括地講，不攜帶有用信息的信號(hào)就是噪聲。顯然，噪聲是相對(duì)于有用信號(hào)而言的，一種信號(hào)在某種場(chǎng)合是有用信號(hào)，而在另一種場(chǎng)合就有可能是噪聲。

數(shù)據(jù)通信是隨著計(jì)算機(jī)和計(jì)算機(jī)網(wǎng)絡(luò)的發(fā)展而出現(xiàn)的一種新的通信方式，它是指信源、信宿處理的都是數(shù)字信號(hào)，而傳輸信道既可以是數(shù)字信道也可以是模擬信道的通信過(guò)程或方式。

通信系統(tǒng)示意圖51單工通信：指消息只能單方向傳輸?shù)墓ぷ鞣绞?，如廣播、遙控等；半雙工通信：指通信雙方都能收發(fā)消息，但不能同時(shí)進(jìn)行收發(fā)，只能分時(shí)工作，如使用同一載頻工作的無(wú)線電對(duì)講機(jī)；全雙工通信：指通信雙方可同時(shí)進(jìn)行收發(fā)消息的工作方式，如普通電話。

點(diǎn)對(duì)點(diǎn)之間的通信又可分為：5253串序傳輸：是將數(shù)字信號(hào)碼元序列按時(shí)間順序一個(gè)一個(gè)地在信道中傳輸；串序傳輸與并序傳輸并序傳輸：是將數(shù)字信號(hào)碼元序列分割成兩路或兩路以上的數(shù)字信號(hào)碼元序列同時(shí)在信道中傳輸。World'stoptenscientificandtechnologicalprogressin2004“Spirit(勇氣)”and“Opportunity(機(jī)遇)”rover（漫游器）landedonMars(火星)andfoundthattherewasevidenceofwater“Cassini(卡西尼)”spacecraftsuccessfullyenteredorbitaroundSaturn(土星)54

DeepSpaceCommunicationsOverviewTheactivitiestoexploretheuniversewillcontinuetogreatlypromotethedevelopmentofthefollowinghumanspaceflightsystems(載人飛行系統(tǒng))sensordesign(傳感器設(shè)計(jì))long-distancetransmissionofinformation(遠(yuǎn)距離信息傳輸)security(安全保障)somanyotheraspectsofengineeringandtechnology.ThefunctionsofSpacecraftcommunicationsSpacecraftcommunicationistomaintainalinkbetweenHumanandthespacecraftSpacecraftcommunicationisanessential(基本)partofSpaceexploration（空間探索）activitiesGuidanceandcontrolSpacecraftSenddetectedscientific（科學(xué)）databacktoEarth55Outerspace(外層空間):thescopeoftheuniverseoutsidetheEarth‘sdenseatmosphere（致密大氣層）,referredtoouterspaceorSpace.Geospace（地球空間）:thespatialextentoftheEarth‘sgravitationalpull（地球引力）,whichbelongstotheplanets（行星）space.(Near-Earthspaceandfar-earthspace)IntheITUWorldRadioAdministrativeConference,todevelopa“RadioRegulations（規(guī)章）",theaveragedistanceoftheEarthtotheMoon(3.844×105km)isdefinedastheboundaryofthenearanddeepspaces.5657Thelate1980s,theboundaryofthenearanddeepspacesisdefinedas2×106kmbyITU.InChina'saerospacesector,thedeepspaceisgenerallydefinedastheouterspacebeyondthemoonincludingthemoon.WhatisDeepSpaceDeepSpaceNoclearuniformdefinitionandclassificationITU's"RadioRegulations“(1988)Thespace,whosedistancefromEarthisgreaterthanorequalto2×106kmChinaEncyclopedia-Aerospacevolume（中國(guó)百科航天篇）Thespace,whosedistancefromEarthisgreaterthanorequaltotheaveragedistanceoftheEarth-Moon(about3.84×105km)ChinaAerospaceWhitePaper（中國(guó)航天白皮書(shū)）Amajorpre-researchobjectofspaceexplorationismoonexploration58

SolarSystem(太陽(yáng)系）：

thesunandalltheplanetsthatgoroundit

GalacticSystem（銀河系）:Verylarge,made

up

of

many

fixed

stars.59WhatisDeepSpaceCommunicationMoontoearthDistance:0.36~0.41×106kmCommunicationDelay:1.21~1.35sSpark(火星)toearthDistance:59.6~401.3×106kmCommunicationDelay:3.3~22.3sPluto(冥王星)toearthDistance:4297.9~7535.1×106kmCommunicationDelay:3.98~6.98h60Distanceandtimedelaybetweenearthandplanets61Spaceradiocommunication:radiocommunicationsbetweenthespacecraftsbeyondtheEarth'satmosphere,betweenthespacecraftandtheearth,orbetweentheearthstationsviathespacecraftrelays.Nearspacecommunication（近空通信）:radio

communicationbe