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Design_0Design

    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

    ;ThentheEarthcenterangleis:

    ;=…s

    ;(]一?

    ;Withthesurfaceareacalculationformula,wecan ;extrapolatesurfaceareaS)coveringtheball: ;()

    ;2

    ;=

    ;2nR

    ;(1

    ;(R

;

    ;-

    ;c.

    ;R

    ;s

    ;co

    ;)

    ;s)(2)

    ;2(1cos)

    ;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.

    ;Table10rbitParametersofmanmadesatellite ;OrbitparametersFunction ;Semimaj.: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 ;usesanellipticalorbitwithlargeeccentricity8.

    ;Toselectthealtitudeoftheperigee.ontheone ;hand.aloweraltitudeisneeded.sothattheSVLBI ;antennaandgroundVLBIantennacanformulatethe ;baselinewiththelargerchangesinlength,whichis ;conducivetothefullcoverageoftheuvplaneofthe

    ;radiosource;ontheotherhand,iftheperigeealtitude ;istoolow,theorbitwillbeaffectedbytheionosphere, ;whichistheoutermostpartoftheearth’satmosphere

;withanaltitudeof601000km.Abovethis.the

    ;electronicdensityisquitelowI.Therefore.thealti

    ;tudechoiceoftheperigeecanbel000km. ;Thehighertheapogeealtitude,thehigheristhe ;resolutionoftheradiosource.However,forthesatel

    ;liteorbitdeterminationbyPPPoftheGNSSsystem. ;theGNSStrackingtimeeciencyshouldalsobe

    ;considered.WithGPSandGalileosatellites,wehave ;summarizedthepositioningPDOPoftheHALCA ;satelliteinoneorbitcycle,fromUTC07h35m ;46.104stol3h53ml2.352sof2003Jan.1.which ;isbeforethetimethatHALCAstoppedsendingdata. ;TheorbitparametersofHALCAcanbefoundin ;References[5,10].Thestatisticsofthepositioning ;PDOPoftheHALCAsatellitebyGPSandGalileoin ;oneorbitcycleisshowninFig.4.fromwhichthe ;conclusionsaredrawrlandshowninTlable2andTa

    ;ble3enthenumberofetrackingGalileoorGPS ;satellitesislessthan4.thenPDOPis0. ;}l

    ;7l

    ;l

    ;

    ;,l

    ;i

    ;{l

    ;.1Il

    ;0246810121416182022

    ;AltitudeOfHALCA/10km

    ;?——

    ;GPSPDOP——GalileoPDOP

    ;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,itisbettertochoosethenonreturnOfcv

    ;clicalrepetitionorbittrack.

    ;5.3Parameters,andM

    ;1)Argumentofperigee:fo.Theargumentofperi- ;geedeterminestheorientationoftheorbitalplaneand ;theperigeeposition,whichischangingorbeselected ;intheO.-360..AnimportanttasktodesignSVLBI ;satellitesistoincreasetheobservationcoverageof ;theradiosourcebytheSouthemHemisphereground ;VLBI.

    ;Fromthenorthsouthdirectionoftheorbit,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.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.basedonorbitdeterminationeciency

    ;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

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