Design
Geo-spatialInformationScience11(1):6-12
;DOI10.1007/sl1806.007.0160.7
;Volume11,Issue1
;March2008
;ArticleID:1009?-5020(2008)01??006?-07Documentcode:A
;DesignofGeodeticSVLBISatellite
;OrbitandItsTrackingNetwork
;WEIErhuLIUJingnanKULKARNIM.N.FREYS6ndor
;AbstractSVLBI(spaceverylongbaselineinterferometry)hassomeimportantpotentialapplicationsingeodesyandgeodynam—
;ics.forwhichoneofthemostdifficulttasksistopreciselydeterminetheorbitofanSVLBIsatellite.Thisworkstudiesseveral
;technologiesthatwillpossiblybeabletodeterminetheorbitofaspaceVLBIsatellite.Then,accordingtothetypesandchara~
;teristicsofthesatelliteandtherequirementsforgeodeticstudyandthegeometryoftheGNSS(GPS,GALILEO)satellitetotrack
;thespaceVLBIsatellite,thesixKeplerianelementsoftheSVLBIsatellite(TEST-SVLBI)aredetermined.Aprogramisdesignedto
;analyzethecoverageareaofspaceofdifferentaltitudesbythestationsofthenetwork,withwhichthetrackingnetworkof
;TEsT_svLBIisdesigned.TheefficiencyoftrackingTESSVLBIbythenetworkisstudied.andtheresultsarepresented.
;KeywordsSVLBI;preciseorbitdetermination;orbitdesign;trackingnetwork ;CICnumberP228.6
;Introduction
;Theuniqueradioastronomicaltechniqueof
;SVLBIisanextensionoftheground.basedVLBI
;intospace.Ithassomeimportantpotentialapplica-
;tionsingeodesyandgeodynamics,includingthe
;definition.practicalrealization.andtheinterconnec.
;tionofdifferentreferenceframes,determiningthe
;geocentricpositionsofVLBIstations,estimationof
;thegravityfieldoftheEarth,andsatelliteorbitde.
;terminationusingthedelayanddelayrateobserv.
;ables.WiththelaunchingofthefirstSVLBIsatellite
;oftheVLBISpaceObservatoryProgram(VS0P)of
;JapaninFebruaryl997.thistechniquehasbecomea
;reality.Aninternationalteamofscientists.working
;undertheauspicesoftheFOMISatelliteGeodesy
;ObservatoryinHungary,hasdesignedtheGEDEX【.
;forthepurposeofexploringthefeasibilityofthe ;geodeticapplicationsofSV.LBI.However,several ;majorproblemsalsoexist.Itisnotsuitableforgeo- ;deticandgeodynamicstudy,whichrequiresprecise ;trackingcapabilitiesresultingincmorbitaccuracy. ;However,theorbitdeterminationofHALCAisac-
2] ;curateto2-5m【
;,
;anditisquitedifficulttobeac.
;curatetol0cm.
;Atpresent,thereisnodedicatedresearchonthe ;designoftheorbitofgeodeticandgeodynamic ;SVLBIsatellite,hencethisworkstudiesseveraltech- ;nologiesthatwillpossiblybeabletodeterminethe ;orbitofthespaceVLBIsatellite.Then,accordingto ;thetypesandcharacteristicsofthesatelliteandthe ;requirementsofpreciseorbitdeterminationforthe ;SVLBIsatellite(TEST-SVLBI),thesixKeplerian ;elementsaredetermined.Also,thetrackingnetwork ;oftheTEST-S:VLBIisdesigned.
;ReceivedonNovember12,2007.,
;FundedbytheNational973ProgramofChina(No.2OO6CB7O13O1),theNationalNatura
lScienceFoundationofChina(No.40774007),andthePro- ;jectofUniversityEducationandResearchofHubeiProvince(No.20053039).
;WEIErhu,SchoolofGeodesyandGeomatics,WuhanUniversity,129LuoyuRoad.Wuhan
43oo79.China;theKeyLaboratoryofGeospaceEnviron—
;mentandGeodesy,MinistryofEducation,WuhanUniversity,129Lu0yuRoad,Wuhan43
OO79,China.
;E-mail:ehwei@s?gg.whu.edu.cn
;
;Orbitdeterminationaccuracy
;andtechniquesofSVLBIsat—
;ellite
;InthereportpreparedbytheRAD10ASTR0N
;Navigation,AstrometryandGeodesy(NAG)Work_ ;ingGroupabouttheprecisenavigationoftheSVLBI ;satellitethefollowingorbitdeterminationaccuracy ;requirementshavebeenspecified.
;11Standardorbit:requiredaccuracybetterthan ;1000m.forsatellitecontrol,orbitprediction,track—
;inganddatacommunication.
;2,Preciseorbit:requiredaccuracybetterthan50m, ;forprocessingground-to-spaceVLBIdata,andmost
;astrometricapplications.
;3)Highlypreciseorbit:requiredaccuracybetter ;than1m,forgeodeticandsomeastrometricapplica—
;tions;requiredaccuracybetterthan0.1m,forgeo—
;dynamicapplications.
;Severalsimulationstudieshavebeenreportedfor ;preciseorbitdeterminationforthedifferentorbitcon—
;figurationspossiblefortheSVLBIsatellites.from ;whichthefollowingtrackingtechniquesanddatatypes ;haveevolvedassomeofthepossiblechoicesforpre—
;ciseorbitdeterminationoftheSVLBIsatellites ;Datalinkbetweenthesatelliteandthetelemetry ;and/orobservinggroundstations:rangeandrangerate; ;VLBIobservations:timedelayanddelayrate;micro—
;wavetrackingsystems:preciserangeandrange.rate ;equipment(PRARE);differenceofrange(DOR) ;tracking:rangedifferenceanddifferencerate;differ—
;enceBI:angulardistancebetweenaradiosource ;andthesatellite,anditschangerate;Laserranging: ;twoway,rangesandonewayranges;on-boardmicro ;accelerometer:non-gravitationalperturbingforceson ;thesatellite;globalpositioningsystem(GPS)tracking. ;ForbothSVLBImissions.VSOPandRAD10AS—
;TR0N.aglobalnetworkoftrackingstationswithin—
;ternationalcollaborationisbeingestablished. ;2Onpreciseorbittechnologies
;ofSVLBlsatellite
;Inthefollowing,accordingtotherequirementof ;lessadditionalestablishmentstodeterminetheorbit ;WEIErhu,eta1./DesignofGeodeticSVLBISatellite…7
;ofanSVLBIsatellitewithhighprecision,several ;technologiesarestudied.
;2.1GPS
;EversincetheintroductionofGPStechnology,a ;revolutionaryeffecttothetraditionalsurveyand ;navigationhasbeenbroughtforward,andithasalso ;becomeanimportantmeanstopreciselydetermine ;theorbitoflow.orbitsatellites.However,atpresent,a ;satellitewithanonboardGPSreceivergenerallyuses ;therelativepositioningmethod(basedonanOTF ;method)todealwiththedoubledifferentialambiguity. ;Therefore,itneedstoarrangeanetworkwithacer- ;taindensityofGPSbasestations,whichwillgreatly ;increasethehuman.materialandfinancialinput,and
;theintensedifficultyinlayingtheglobalterrestrial ;basestations.Inaddition,theSVLBIbaselinelength ;maybe1000-10000km,andtheOTFmaynolonger ;workwell,hencetheprecisionoftheSVLBIsatellite ;orbitsdeterminedbyGPSpositioningwillsharply ;decline.
;In1997,Zumbegerintroducedthesinglepointpre. ;cisepositioningtechnology(PPP).Reference[4]has ;discussedthegeometricPPPorbitdeterminationof ;theCHAMPsatellitefromonboardGPSdata.The ;resulthasshownthattheaccuracyonradialis30.40 ;cm.andontangentornormalisbOm10-20cm.Also, ;thepaperhasanalyzedthedynamicorbitsmoothing ;basedonthePPP.andhaspresentedasemi-parameter ;orbitsmoothingmethodthatusesanon-parameteritem ;tOabsorbdynamicerror.Theresulthasshownthatthe ;accuracyonradia1.ontangentandnormaldirections ;arerespectivelylessthan18cm.8cmand12cm.To ;useaGPSsystemforpreciseorbitdeterminationofan ;SVLBIsatellite.wedownloadedthebroadcasting ;ephemerisdocumentsofaGPSsatelliteat0:00a.m.on ;July21,20051:58(GPStime)fromtheNASAwebsite, ;inRINEXformat.fromwhichtheKeplerianorbital ;parametersofGPSsatellitesareextracted. ;2.2Galileo
;Thelackofredundantsatellitesisoneoftheobsta. ;clesforsatelliteorbitdeterminationwithanon.board ;GPSsystem.Thecharacteristicsofhigherorbitposi- ;tions(24000km)andalargenumberofsatellites(27) ;oftheGalileosystemwillbeveryhelpfulfororbit ;
;8Geo-spatialInformationScience11(1):6-12 ;determinationofSVLBIsatelliteswithon.board ;Galileoreceivers.ontheonehand.inthesameorbit ;altitudetoreceivemorenavigationsatellitesignals ;forimprovingtheaccuracyoforbits;andontheother ;hand,toreceiveadequatenavigationsatellitesignals ;atahigherorbit.TousetheGalileosystemforprecise ;orbitdeterminationofSVLBIsatellites.wehaveex. ;tractedtherelevantsatelliteKeplerianorbitalparame. ;ters(orbitalmoment:2004.01.01TOO:OO:OOUTCG1 ;fromhttp://www.gssf.info/.
;3Coverageoftrackingnetwork
;andsoftware
;3.1Coverageoftrackingnetwork
;Thescopeofatrackingnetworkisaspacecover- ;agescopetrackedbythenetwork,whichisanimpor—
;tantindicatortomeasurethequalityofthedesigned ;network.
;Theworkregionofthetrackingnetworkisthe ;spacetrackingregionthatthestationsofthenetwork ;canprovidetrackingandcommunicationsserviceto ;thesatellites.Theworkregioncoverageofthenet—
;workistheprojectionofthespacetrackingregionon ;thesurfaceoftheEarth.TheEarthisnotabodyin ;mathematicalrules,towhosesurfacethedirectpro—
;jectioncannotbeprocessed.However,thesurfaceof ;theEarthisclosetoaspheroidorellipsoidball,to ;whichtheworkregionofthenetworkcanbepro—
;jectedandsimplycalculated.
;Thesatelliteistrackedatanelevationangle:the ;smallertheis,thelongertrailstheatmospheric ;wavesacross,butthegreaterthewavesdecay,and ;thereforetheusefulsignalsreceivedbythetracking ;stationsareweakened.Toensurethecommunications ;andtrackingefficiencyofthetrackingstationstothe ;satellite,alowerlimitisoftengiven,whichisgen—
;erally8=5*-10..When?.thecommunicationof
;thestationsareconsideredinvalid.Thenthecorre. ;spondingspacetrackingregionbytrackingstationsis ;showninFig.1.Theprojectedsphericalcoverageis ;thecircleonthespheroidsurfacewhosecenterisa ;trackingstationwithasphericalradiustoS1or’S2
;ontheballsurface.Atanaltitude?ofthesatellite.
;thegroundcoverisshowninFig.2.
;Fig.1Spacetrackingregionbyastation
;Fig.2Thegroundcoveredbyasatellite
;ThentheEarthcenterangle舀is:
;=…s
;(]一?
;Withthesurfaceareacalculationformula,wecan ;extrapolatesurfaceareaS)coveringtheball: ;()
;2
;=
;2nR
;(1
;(R
;一
;-
;c.
;R
;s
;co
;)
;s)(2)
;2(1一cos)一
;WeusetheMercator’sprojectiontoconvert
;sphericalmapstoaplane. ;WehaveeditedtheNE’ICovPlotsoftwaretocal-
;culateandmapthegroundcoverageoftheworkarea
;oftrackingnetwork,tofacilitatethevisualizationde— ;signofthetrackingnetworkforspacevehiclesin
;differentheights.Thesoftware’sdiagramisshownin
;Fig.3.
;4Parametersandtypesofsatel- ;Iiteorbit
;4.1Satelliteorbitparameters ;Intheartificialsatelliteorbittheory,thesixKeple—
;
;Begin
;Enterthemeanaltitudeand ;minimumelevationan~le ;Enterthematerialsof
;thetrackingstation
;Computethegroundcoverage, ;Mercatorproj’ection
;Showthestationandcoverage ;9ntheworldmap
;End
;Fig.3Softwarediagram ;rianparametersareoftenusedtodescribetheshape,
;thesizeandtheorientationinspaceoftheelliptical
;orbittodeterminethelocationofthesatellite,which
;arelistedinTlable1.
;Table10rbitParametersofman—madesatellite ;OrbitparametersFunction ;Semi—maj.:a
;Eccentricity:e
;Inclination:f
;RAofnode:Q
;Arg.ofperigee:?
;Meananomaly:M
;Describetheshapeandsizeof
;theorbit
;Describethepositionoftheorbit
;plane
;Describetheorientationinspace
;oftheellipticalorbitintheorbit
;plane
;Describethepositionofthesat.
;elliteintheorbit
;4.2Thetypesofsatelliteorbit
;WiththelinkingofthesatelliteandtheEarthcen—
;ter,theintersectionpointofthelinkinglineand ;groundsurfaceiscalledasubsatellitepoint.When ;thesubsatellitepointsarelinked,theywillforma ;trackontheground,whichiscalledsubsatellitepoint ;trajectory,Bythesatellite’sorbitalelementsandthe
;characteristicsofsubsatellitepointtrajectory,and ;withintheearthgravitationalcondition,thesatellite ;orbitcanbedividedintothecategories[】:
;1)sortingbyeccentricityoftheorbit;
;2)sortingbyinclinationoftheorbit;
;3)sortingbyheightoftheorbit;
;4)sortingbythemovingangularvelocityofthe ;orbitplane;
;5)sortingbytherepetitionofthesubsatellitepoint ;trajectory;
;6)sortingbytherelationshipbetweenearthrota—
;tionandsatelliteorbitalcycle.
;WEIErhu,eta1./DesignofGeodeticSVLBISatellite…9
;5DesignofSVLBIsatelliteorbit
;5.1Shapeandsize
;TheSVLBIsatelliteisrequiredtomeettheneeds ;ofgeodesyandastrometry,soitisclassifiedasanex—
;plorationsatelliteofspatialscience,whichgenerally ;usesanellipticalorbitwithlargeeccentricity【8】.
;Toselectthealtitudeoftheperigee.ontheone ;hand.aloweraltitudeisneeded.sothattheSVLBI ;antennaandgroundVLBIantennacanformulatethe ;baselinewiththelargerchangesinlength,whichis ;conducivetothefullcoverageoftheu—vplaneofthe
;radiosource;ontheotherhand,iftheperigeealtitude ;istoolow,theorbitwillbeaffectedbytheionosphere, ;whichistheoutermostpartoftheearth’satmosphere
;withanaltitudeof60—1000km.Abovethis.the
;electronicdensityisquitelowI.Therefore.thealti—
;tudechoiceoftheperigeecanbel000km. ;Thehighertheapogeealtitude,thehigheristhe ;resolutionoftheradiosource.However,forthesatel—
;liteorbitdeterminationbyPPPoftheGNSSsystem. ;theGNSStrackingtimee所ciencyshouldalsobe
;considered.WithGPSandGalileosatellites,wehave ;summarizedthepositioningPDOPoftheHALCA ;satelliteinoneorbitcycle,fromUTC07h35m ;46.104stol3h53ml2.352sof2003Jan.1.which ;isbeforethetimethatHALCAstoppedsendingdata. ;TheorbitparametersofHALCAcanbefoundin ;References[5,10].Thestatisticsofthepositioning ;PDOPoftheHALCAsatellitebyGPSandGalileoin ;oneorbitcycleisshowninFig.4.fromwhichthe ;conclusionsaredrawrlandshowninTlable2andTa—
;ble3讳enthenumberofetrackingGalileoorGPS ;satellitesislessthan4.thenPDOPis0. ;}l
;7l
;l
;一
;,l
;i
;{l
;.1Il
;0246810121416182022
;AltitudeOfHALCA/10km
;?——
;GPS—PDOP——Galileo—PDOP
;Fig.4PositioningPDOPofHALCAbyGPSandGalileo ;086420
;00
;
;10Geo-spatialInformationScience11(1):6-12 ;Table2StatisticsofpositioningbyGPS ;Table3StatisticsofpositioningbyGalileo ;Toaccuratelydesigntheapogeeheight,itwould ;involveseveralotherorbitalparameters.Therefore, ;thesatellite’sapogeeheightwillbedeterminedafter
;thedeterminationofotherparameters. ;5.2Choiceoftherepetitionofthesatellite ;trajectory
;OneofthedevelopingdirectionsOfICRFistoex—
;pandthenumberandspatialdistributionoftheradio ;sourceandthetaskofSBIrequiresobservations ;anddefinitionofthepossibleradiosourcescovering ;thespaceinalldirectionstoincreasethemeasuring ;quantityandtoimprovethegeometricprecision.In ;thisway,itisbettertochoosethenon—returnOfcv—
;clicalrepetitionorbittrack.
;5.3Parameters,andM
;1)Argumentofperigee:fo.Theargumentofperi- ;geedeterminestheorientationoftheorbitalplaneand ;theperigeeposition,whichischangingorbeselected ;intheO.-360..AnimportanttasktodesignSVLBI ;satellitesistoincreasetheobservationcoverageof ;theradiosourcebytheSouthemHemisphereground ;VLBI.
;Fromthenorth—southdirectionoftheorbit,the
;apogeeshouldbeselectedinthemostsouthempart ;oftheorbit,sotheperigeeistothemostnorthemend. ;Inthisway,inoneorbitcycleofthesatellite,mostof ;thetimeistakenfortheskyobservationinthesouth—
;emhemisphere.Therefore,itisarguedthattheperi—
;geeshouldbe90..
;2)RAofnode(Q)andmeananomaly(.The
;rightascensionofnode(Q)determinestheorbitloca—
;tionintheorbitalplane.Themeananomaly(de- ;terminesthelocationofsatellitesintheorbitatany ;moment.BothofthesechangeinO.一360..sowecan
;onlychoosetheinitialvalueforthem.
;Basedontheaboveanalysis,o9,QandMare
;changing,whichcanonlybedesignedataparticular ;moment.Forexample,themomentoforbitparame—
;tersisselectedtobe(1Jan.2006,00h00m00.00s, ;UTC),whenQis193.24822o,?is90.,andMis
;lOO..
;5.4Altitudedesignoftheapogee
;TheorbitalaltitudeofGalileosatellitesishigher ;thanthatofGPS.andwefocusontheuseofthe ;GalileosystemtopreciselydetermineSVLBIorbit ;anddeterminationoftheaDogeealtitude.Sowewill ;selecttheapogeeheightbetween15000kmand ;20000km.basedonorbitdeterminatione衔ciency
;withtheGalileosystem,andtheotherparameters ;remainunchanged.TheconclusionsarelistedinTa—
;ble4.So,theapogeealtitudeshouldbel5000km. ;Table4Orbitdeterminationefficiency ;Apogee
;altitude
;Orbitdeterminingtechnologyandeffi- ;ciency(oneorbitcycle)/%
;GalileoGPS
;6Orbitdirectionandinclination
;Thechoiceofthedirectorbitishelpfultoreduce ;energyrequirementsofvehicleswithEarthrotation ;speed【『J.Also.thisdirectorbitcanextendtheobser- ;vationtimeofSVLBIandgroundVLBIstationan—
;tennabyusingtheEarth’srotation,andsothequan—
;tityofobservationsisincrea