第三章卫星信号及位置计算

吉长东(qq群:4042615,email:[e-mail])辽宁工程技术大学测绘工程系GPS技术及应用•GPS的组成•卫星运动及其轨道•GPS信号及导航电文•GPS卫星在轨位置的计算第三章GPS系统及其信号吉长东(qq群:4042615,email:[e-mail])辽宁工程技术大学测绘工程系GPS技术及应用GPS的组成•由三部分组成–空间部分–地面部分–用户部分GPS的系统组成GLONASS:卫星星座、地面监测控制站和用户设备Galileo:空间段、地面段和用户吉长东(qq群:4042615,email:[e-mail])辽宁工程技术大学测绘工程系GPS技术及应用GPSsegmentsGPSconsistsofthreesegments:thespacesegmentthecontrolsegmentandtheusersegment中国北斗两颗地球同步卫星（GEO）、地面中心站、用户终端吉长东(qq群:4042615,email:[e-mail])辽宁工程技术大学测绘工程系GPS技术及应用ThespacesegmentConsistsofthe24-satelliteconstellationintroducedintheprevioussection.EachGPSsatellitetransmitsasignal,whichhasanumberofcomponents:twosinewaves(alsoknownascarrierfrequencies),twodigitalcodes,andanavigationmessage.Thecodesandthenavigationmessageareaddedtothecarriersasbinarybi-phasemodulations双向调制.Thecarriersandthecodesareusedmainlytodeterminethedistancefromtheuser‘sreceivertotheGPSsatellites.Thenavigationmessagecontains,alongwithotherinformation,thecoordinates(thelocation)ofthesatellitesasafunctionoftime.Thetransmittedsignalsarecontrolledbyhighlyaccurateatomicclocksonboardthesatellites.吉长东(qq群:4042615,email:[e-mail])辽宁工程技术大学测绘工程系GPS技术及应用Thecontrolsegment•oftheGPSsystemconsistsofaworldwidenetworkoftrackingstations,withamastercontrolstation(MCS)locatedintheUnitedStatesatColoradoSprings,Colorado.TheprimarytaskoftheoperationalcontrolsegmentistrackingtheGPSsatellitesinordertodetermineandpredictsatellitelocations,systemintegrity,behaviorofthesatelliteatomicclocks,atmosphericdata,thesatellitealmanac,andotherconsiderations.ThisinformationisthenpackedanduploadedintotheGPSsatellitesthroughtheS-bandlink.吉长东(qq群:4042615,email:[e-mail])辽宁工程技术大学测绘工程系GPS技术及应用Theusersegmentincludesallmilitaryandcivilianusers.WithaGPSreceiverconnectedtoaGPSantenna,ausercanreceivetheGPSsignals,whichcanbeusedtodeterminehisorherpositionanywhereintheworld.GPSiscurrentlyavailabletoallusersworldwideatnodirectcharge.吉长东(qq群:4042615,email:[e-mail])辽宁工程技术大学测绘工程系GPS技术及应用GPSsatellitegenerationsGPSsatelliteconstellationbuild-upstartedwithaseriesof11satellitesknownasBlockIsatellites(Figure1).Thefirstsatelliteinthisseries(andintheGPSsystem)waslaunchedonFebruary22,1978;thelastwaslaunchedonOctober9,1985.BlockIsatelliteswerebuiltmainlyforexperimentalpurposes.Theinclinationangleoftheorbitalplanesofthesesatellites,withrespecttotheequator,was63°,whichwasmodifiedinthefollowingsatellitegenerations.Figure1吉长东(qq群:4042615,email:[e-mail])辽宁工程技术大学测绘工程系GPS技术及应用AlthoughthedesignlifetimeofBlockIsatelliteswas4.5years,someremainedinserviceformorethan10years.ThelastBlockIsatellitewastakenoutofserviceonNovember18,1995.ThesecondgenerationoftheGPSsatellitesisknownasBlockII/IIAsatellites(Figure1).BlockIIAisanadvancedversionofBlockII,withanincreaseinthenavigationmessagedatastoragecapabilityfrom14daysforBlockIIto180daysforBlockIIA.ThismeansthatBlockIIandBlockIIAsatellitescanfunctioncontinuously,withoutgroundsupport,forperiodsof14and180days,respectively.Atotalof28BlockII/IIAsatelliteswerelaunchedduringtheperiodfromFebruary1989toNovember1997.Ofthese,23arecurrentlyinservice.UnlikeBlockI,theorbitalplaneofBlockII/IIAsatellitesareinclinedby55°withrespecttotheequator.吉长东(qq群:4042615,email:[e-mail])辽宁工程技术大学测绘工程系GPS技术及应用ThedesignlifetimeofaBlockII/IIAsatelliteis7.5years,whichwasexceededbymostBlockII/IIAsatellites.Toensurenationalsecurity,somesecurityfeatures,knownasselectiveavailability(SA)andanti-spoofing（A-S）,wereaddedtoBlockII/IIAsatellites.AnewgenerationofGPSsatellites,knownasBlockIIR,iscurrentlybeinglaunched(Figure1).Thesereplenishment(替补)satelliteswillbebackwardcompatible（适合）withBlockII/IIA,whichmeansthatthechangesaretransparenttotheusers.BlockIIRconsistsof21satelliteswithadesignlifeof10years.Inadditiontotheexpectedhigheraccuracy,BlockIIRsatelliteshavethecapabilityofoperatingautonomouslyforatleast180dayswithoutgroundcorrectionsoraccuracydegradation（降低）.Theautonomousnavigationcapabilityofthissatellitegenerationisachievedinpartthroughmutual（相互）satelliterangingcapabilities.吉长东(qq群:4042615,email:[e-mail])辽宁工程技术大学测绘工程系GPS技术及应用Inaddition,predictedephemerisandclockdataforaperiodof210daysareuploadedbythegroundcontrolsegmenttosupporttheautonomousnavigation.Morefeatureswillbeaddedtothelast12BlockIIRsatellitesundertheGPSmodernizationprogram,whichwillbelaunchedatthebeginningof2003（施加？）.AsofJuly2001,sixBlockIIRsatelliteshavebeensuccessfullylaunched.BlockIIRwillbefollowedbyanothersystem,calledBlockIIF(for“follow-on”),consistingof33satellites.Thesatellitelifespanwillbe15years.BlockIIFsatelliteswillhavenewcapabilitiesundertheGPSmodernizationprogramthatwilldramatically（引人注目）improvetheautonomousGPSpositioningaccuracy.ThefirstBlockIIFsatelliteisscheduledtobelaunchedin2005（发射没？？）.吉长东(qq群:4042615,email:[e-mail])辽宁工程技术大学测绘工程系GPS技术及应用GPS的系统组成空间部分•GPS卫星星座–设计星座：21+3•21颗正式的工作卫星+3颗活动的备用卫星•6个轨道面，平均轨道高度20200km，轨道倾角55，周期11h58min（顾及地球自转，地球-卫星的几何关系•每天提前4min重复一次）•保证在24小时，在高度角15以上，能够同时观测到4至8颗卫星–当前星座：28颗？？空间部分•卫星轨道高度和周期：Glonass•19100km，•11h15minGalileo•23616km,•14h4min北斗导航（CNSS）36000km12