the contribuons of satellite laser ranging to satellite almetry · 2016. 10. 19. · 1 the...
TRANSCRIPT
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TheContribu-onsofSatelliteLaserRangingtoSatelliteAl-metry
FrankG.LemoineNASAGoddardSpaceFlightCenter
October12,2016
20thInterna+onalWorkshoponLaserRangingPotsdam,Germany
WithcontribuBonsfromN.Zelensky(SGT@NASAGSFC),A.Couhert(CNES,Toulouse)
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•Introduc+on•ThescienceofSatelliteAl+metry.•Role&Contribu+onofSLR.(1)POD.(2)ITRF.(3)Geocenter.(4)Time-VariableGravity.(5)OrbitValida+on..•Somecurrentchallenges.
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POD-Schema-c
Inordertodeterminetheheightoftheseasurface,wemustknowthesatelliteposi-on(meaningitsorbitalephemerides)toaprecisioncommensuratetoorbeFerthantheaccuracyoftheal-meter
ThisexampleisforTOPEX,butthesameprincipleappliesforallal-metersatellites.
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Example Ground Track Coverage for TOPEX (& Jason-1, Jason-2, Jason-3)
ImagefromAVISO(Toulouse,France) Al-tude1336km.Inclin.=66.039°;Groundtrackrepeat:9.9156days.Cross-tracksepara-on(equator):315km
TOPEX/Poseidon 1992-2006
Jason-3 2016 –
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Example: Ground Track Coverage for TOPEX vs. ERS/Envisat
Al-tude~785km.Inclin.98.543°;(sun-synchronous)Groundtrackrepeat:35days.Cross-tracksepara-on(equator):80km
TOPEX/Jason-1,2,3 ERS&Envisat&SARAL
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•Introduc+on•ThescienceofSatelliteAl+metry.•Role&Contribu+onofSLR.(1)POD.(2)ITRF.(3)Geocenter.(4)Time-VariableGravity.(5)OrbitValida+on.•Somecurrentchallenges.
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ScienceofAl-metry-IMeanSeaSurface
Meandisplacementoftheseasurfacefromareferenceellipsoid;FollowsthegeoidoftheEarthandincludesthedynamicoceantopography.MSSareconstructedfrommanyyearsofsatelliteal-metryanddatafromdifferentsatellites:E.g.TOPEX/Poseidon,Jason,ERS-2,ENVISAT
DNSC08MSS&DTU10(DTUSpace)(Andersen&Knudsen,JGR,2009,doi:10.1029/2008JC005179)
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ScienceofAl-metry-IIDynamicOceanTopography
Withindependentinforma-ononthegravityfieldoftheEarth(e.g.GOCE)itispossibletoseparateouttheDOTcontribu-ontoaMeanSeaSurfaceandimagethemeanshapeoftheoceanscausedbytheoceancurrents...andalsocomputethemeangeostropicveloci-es.(a) GOCEDOTfilteredwitha140kmGaussianfilter(b) SurfacegeostrophiccurrentspeedscomputedfromthefilteredGOCEDOT.(Knudsen,P.,etal.,“Aglobalmeandynamictopographyandoceancircula-ones-ma-onusingapreliminaryGOCEgravitymodel”,J.Geodesy,2011)
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(GeodynamicsandEarthOceanSatellite:GEOS-3)Launched:Apr.9,1975OperatedthroughJuly1979.
B.Douglasetal.,JGR,1983,hFp://dx.doi.org/10.1029/JC088iC14p09595
ScienceofAl-metry-IIIGulfStreamMeanVeloci+es:Al+metry+gravityfromGOCE
Sanchez-Reales,etal.,2012,MarineGeodesy.
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ThepreciseorbitsforTOPEX/Poseidon,Jason-1,Jason-2,allcomputedinaconsistentreferenceframe(ITRF2008,andinfutureITRF2014)areusedtocomputetheglobalchangeinmeansealevelfromsatelliteoceanradaral-meterdata.
hcp://podaac.jpl.nasa.gov/Integrated_Mul+-Mission_Ocean_Al+meterData
ScienceofAl-metry-IV
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ScienceofAl-metry-V
Regionalmeansealevelvaria+onsfromTOPEX,Jason-1,andJason-2withrespectto1993-2002mean;hcp://podaac.jpl.nasa.gov/Integrated_Mul+-Mission_Ocean_Al+meterData
MeasurementofRegionalandGlobalMeanSeaLevelChange
TOPEX/Poseidon 1992-2002 (-2006)
Jason-1, 2001-2009 (-2013) Jason-2, 2008- Jason-3, 2016-
1993-2016
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ScienceofAl-metry-VIElNino:1997(TOPEX/Poseidon)vs.2015(Jason-2)
Seeupdatesevery~10daysathcp://sealevel.jpl.nasa.gov/science/elninopdo/latestdata/archive/
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ScienceofAl-metry-VIIHurricaneIntensifica+onfromPassageoverWarmCoreEddies
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32˚N 32˚N
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CU CCAR Sea Surface Height (cm) 08/27Max winds in miles/hr
hFp://oceanmo-on.org/html/impact/natural-hazards.htmhFp://www.nasa.gov/centers/jpl/news/ostm-20080701.html
MappingofGulfofMexicoSeaSurfaceHeightVaria-onsbyDr.RobertR.Leben,UniversityofColorado,Boulder.
SeaSurfaceHeightvaria-onsshowtheloca-onofwarmwatereddies–whichappearhigherinabsoluteheight.Theirlatentheightcancontributetohurricaneintensifica-on.
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Oceanographic&GeophysicalSignalSummary
Phenomenon Amplitude
MeanSeaSurface ±~100m Geoid+D.O.T.
GlobalDynamicOceanTopography
±~1.5m Onlyresolvablewithindependentsatellitegravityinforma-on
SeaLevelChange ~3mm/yr(globalaverage)
Regionalvaria-ons
WarmCoreEddies ~50cm e.g.HurricaneKatrina
ElNino ±~30cm
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Oceanographic&GeophysicalSignalSummary
Phenomenon Amplitude
MeanSeaSurface ±~100m Geoid+D.O.T.
GlobalDynamicOceanTopography
±~1.5m Onlyresolvablewithindependentsatellitegravityinforma-on
SeaLevelChange ~3mm/yr(globalaverage)
Regionalvaria-ons
WarmCoreEddies ~50cm e.g.HurricaneKatrina
ElNino/LaNina ±~30cm aperiodic(inter-annual)phenomenon.
Requirementsfororbitaccuracy:TOPEX/Poseidon•ini-alorbiterrorbudget:~13cm(Tapleyetal.,1994,JGR-Oceans).•Achieved2.5cmby1994(tunedgravitymodel,JGM-2,JGM-3)•PostprocessingITRF2005&ITRF2008;GRACEgravitymodels):1.5-2.0cmorbits.Jason-1->Jason-3•Goalis1cmradialorbiterroraccuracy!!***REQUIRESVERIFICATION****•Wemustalsohaveanorbitthatisstableenoughtoaccuratelymeasureglobalandregionalchangesinmeansealevel
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OrbitStabilityrequirement(global®ionalmeansealevel)
AblainM.etal.,“Improvedsealevelrecordoverthesatelliteal-metryera(1993–2010)fromtheClimateChangeIni-a-veproject”OceanSci.,11,67–82,2015
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•Introduc+on•ThescienceofSatelliteAl+metry.•Role&Contribu+onofSLR.(1)POD.(2)ITRF.(3)Geocenter.(4)Time-VariableGravity.(5)OrbitValida+on.(6)(ModelValida+on).•Somecurrentchallenges.
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FirstLaserRanging,Oct.31,1964,NASAGSFC
GEOS-3
SEASAT, 1978
ERS-1 ERS-2
Envisat
TOPEX,Jason1,2,3
Representa+veSLRprecisionvs.+me
AdaptedfromJ.Degnan.“ImpactofSLRTechnologyInnova-onsonModernScience”,18thILRSWorkshop,Fujiyoshida,Japan,Nov.11,2013.hFp://cddis.gsfc.nasa.gov/lw18/docs/presenta-ons/Session0/13-0001-Degnan_2.pdf
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Onaverageweobtain20-30passes/dayfromthedifferentsta-onsoftheglobalILRSnetwork.
Onaverage20-30sta-onshavetrackedTP,J1,J2&J3perday
SLR–TP,J1,J2,J3trackingsummary
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TrackingDataforAl-meterPOD
SLR
DORIS
TOPEX,Jason-1,Jason-2,Jason-3(en-re-mespan:1993-2016)
TOPEX,Jason-1,Jason-2,Jason-3(NoDORISonTOPEX:2004-2006)
GPS TOPEX(1993-1994only.Demo.)Jason-1(2001-2006)Jason-2,(July2008-present)Jason-3:(Jan.2016-present)
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SLR–TP,J1,J2RMSResiduals
TOPEXLRA.(Schwartz,AppliedOp-cs,1990)
LRAforJason-1,Jason-2,Jason-3(courtesyoftheILRS)
SLRRMSResidualstoNASAGSFCstd1504orbitsforTOPEX/Poseidon,Jason-1,Jason-2.
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SLR–J2&J3RMSResiduals
LRAforJason-1,Jason-2,Jason-3(courtesyoftheILRS)
SLRRMSResidualstoNASAGSFCstd1504orbitsforJason-2andJason-3duringtandemcalibra+onperiod(February–September2016)(fromN.Zelensky,SGT@NASAGSFC)
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SLR–J1&J2OrbitAccuracyAchievedJason-1andJason-2RadialRMSOrbitDifferencesby10-daycycle(2002-2014)
(DifferencesbyOrbitTypeandbyAnalysisCenters)
Couhert,A.,etal.,“Towardsthe1mm/ystabilityoftheradialorbiterroratregionalscales”,Adv.SpaceRes.,2015,doi:10.1016/j.asr.2014.06.041.
NASAGSFCvs.JPLvs.CNESvs.ESOCSLR/DORIS(NASAGSFC)vsGPS-only(JPL)vs.GPS+DORIS+SLR(ESOC)vs.GPS+DORIS+SLR(CNES-GDR-D)
JASON-1
JASON-2
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SLR–Valida-onofJason-2GPS&DORISorbits
Thefactthattheseorbitsfromdifferenttrackingsystemsagreeat~1cmradialRMS,isareasonwhywecanhavesuchhighconfidenceinthedetermina+onofMeanSeaLevelchangefromsatelliteal+metry.
InthesetestswithDORIS&GPSdata,SatelliteLaserRangingMeasurementsofJason-2areindependentanddirectlymeasureorbitaccuracy.
SLRRMSoffit(Coresta+ons,Alleleva+ons)forCNESGDR-Eorbits(basedonDORIS+GNSS,reduced-dynamicorbits)(fromAlexandreCouhert,CNES)
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SLR–Evalua-onofDORIS-onlyorbits(Saral)
(Zelenskyetal.,2016,“Towardsthe1-cmSARALorbit”,Adv.SpaceRes,doi:10.1016/j.asr.2015.12.011)
Athigheleva-onsSLRmeasuresdirectlytheradialorbiterror;Sointhisexample,wecansaytheDORIS-onlyorbitsonSARALhaveanorbitalaccuracyof10-15mm.
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SLR–Contribu-ontoITRF
FiguresfromZuheirAltamimi,IGN/France
Areferenceframerealiza-onconsistsofposi+onsandveloci+esofthereferencepoints.ForITRF2014,post-seismicrelaxa-onisalsomodeledforthefirst-me.
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SLR–Contribu-ontoITRF
FiguresfromZuheirAltamimi,IGN/FranceSeealsoAltamimietal.(2016)
SLRcontributestotheoriginandscaleoftheterrestrialreferenceframeaswellasposi-on/velocityofkeyreferencepoints(coreSLRsta-ons).
ILRS/SLRorigincomponentswrt.ITRF2014
VLBISLR
SLR/VLBIscaleswrt.ITRF2014
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TP,J1,J2,J3.PrimedataforMeasureofchangeinglobalMeanSeaLevel.(Keyclimateindicator).•Mustbedeterminedinastable&consistentreferenceframe•ITRF2008atpresent.(ITRF2014resultsbyOSTSTInLaRochelleNov.2016)•OnlySLR&DORISspanen+re+meseries!!(GPSonTOPEX:1993-1994only;GPSonJason-1:2001-2006;GPSonJason-2:2008-present).
ITRF&MeanSeaLevel
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Regional TOPEX (1993-2002) Sea Surface Height Trend differences from direct impact of the ITRF2005 (GGM02C) minus CSR95 (JGM3) orbit differences. (from Beckley et al., Geophys. Res. Lett., 2007). Errors in the Z component of the TRF can produce large regional errors in MSL rate determination.
MeanSeaLevel:ImpactofTRFerror
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SLR–Geocenter&Al-metryPOD(I)
InthesolidEarthcenterofmassframe,geocentermo-onoftheTotalEarth’smassreferencedtoCF:
rc(t) = rcm(t)–rcf(t)
rcm(t): displacementofthecenterofmass(CM)largelyduetoredistribu+onofcon+nentalwater,atmosphericandoceanicmassattheEarth’ssurface.
rcf(t): displacementofthecenteroffigure(CF)dueinlargeparttoelas+cdeforma+onoftheEarth’ssurfacecausedbyloading. Note.TheSLRcenterofnetwork(CN)becomesthe
centeroffigure(CF)originintheSLRgeocenteres+mate.
L1/L2GeocenterSolu+onfromRies(2013)
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SLR–Geocenter&Al-metryPOD(II)
CSRCMmodellargelyremovesannualZdifferencesignaturebetweenSLR/DORIS&JPL13a/GPSReduced-dynamicorbits
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SLR–Time-VariableGravity(1)
•SLRcontributestodetermina-onofthe-me-variablegravityvaria-onsoftheEarth.•Pre-GRACE–itistheprimarysourceofinforma-onforlowdegreeterms.•IneraofGRACE---determina-onofzonalterms(C20,C40)–towhichGRACEdataarerela-velyinsensi-veorstronglyaliasedwithS2-likesignal.
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SLR–Time-VariableGravity(1)
1990 1995 2000 2005 2010 2015−2
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2 x 10−10 c22
9c5CSR SLR
NASAGSFCSLR+DORIS-derivedTVG+meseriesvs.CSR/SLR/RL05series.
C22
4x4&5x5-meseriesdeveloped@NASAGSFCforal-metrysatellitePOD,andforDORISreprocessingassociatedwithITRF2014.
IMPROVEMENTSEENBYSLR(TP,J1,J2)
(Lemoineetal.,2014,OSTST)
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SARAL, 2013-
CRYOSAT-2, 2010- Jason-2, 2008- Jason-3, 2016-
ISRO (India)
Haiyang (HY)-2A, 2011
(CNSA) Sentinel-3A
2016
CurrentOcean-radarmappingal+metersatellites(Oct.2016)
SLR+DORIS+GNSSSLR+DORIS
SLR+DORIS
(SLR)+DORIS+GNSS
SLR+DORIS+...(GNSS*)
Thesesatellitesforma“virtual”constella+onthatmonitorstheoceansurfacetopography.GoldenAgeofSatelliteAl+metry!!
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Summary:Whydoweneedmul+pletrackingsystems?
15Space Geodesy Applications, June 7, 2012
Whydoweneedmul-pletrackingsystems?
We need multiple tracking systems (a) to ensure and establish orbit accuracy; This is especially important for the demanding application of measurement of the change in global mean sea level & to demonstrate orbit accuracy. (b) to ensure redundancy; in the event one tracking system has “problems”, or even fails. (I) GFO. Failure of GPS. SLR + altimeter crossovers only reliable tracking system. (II) Jason-1. DORIS Oscillator not hardened before launch – perturbed by passage through S. Atlantic anomaly, Apply a “correction” model.
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SLR–ModelImprovement&Valida-onforAl-meterSatellites(Examples)
1. ImprovementsinTime-variablegravitymodeling,andintheITRF.
CouhertAetal.(2015)“Towardsthe1mm/ystabilityoftheradialorbiterroratregionalscales”,Adv.SpaceRes.,doi:10.1016/j.asr.2014.06.041.2.ImprovementinNon-conserva+veforcemodelling.Zelenskyetal.,(2010).“DORIS/SLRPODmodelingimprovementsforJason-1andJason-2”,Adv.SpaceRes.,doi:10.1016/j.asr.2010.05.0083. TuningofphasemapsforGPS-satellitereceivers:LuthckeS.etal.(2003),MarineGeodesy,“The1-cmOrbit:...”HainesBr.etal.(2004),MarineGeodesy,“OnecmPODforJason-1...”MercierFl.etal.(2009),OSTSTmee+ng,SeaFleWashingtonJune2009.4. MonitoringPerformanceofDORIS/USOonJason-2
usingT2L2instrument.BelliA.etal.,inpress(2016).“Temperature,radia+onandaginganalysisoftheDORISUltraStableOscillatorbymeansoftheTimeTransferbyLaserLinkexperimentonJason-2”,Adv.SpaceRes.,doi:10.1016/j.asr.2015.11.025.
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•Introduc+on•ThescienceofSatelliteAl+metry.•Role&Contribu+onofSLR.(1)POD.(2)ITRF.(3)Geocenter.(4)Time-VariableGravity.(5)OrbitValida+on.(6)ModelValida+on.•Somecurrentchallenges.
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SLR–CurrentChallenges:SLRbiases
Challenge:WeuseSLRdatatovalidatetheperformanceofDORIS-onlyandGPS-onlyorGPS+DORISorbits(e.g.CNESGDR-E).WealsowishtousetheSLRdatatomonitorlong-termdrixsintheorbits.SLRbiasesinterferewithandcomplicatethisdirectorbitaccuracyvalida-on.Thisisconfoundedby(possible)referenceframeissues(GPSvs.SLR)andpossiblevelocityerrorsofsta-ons.
Couhert,A.,etal.,“Towardsthe1mm/ystabilityoftheradialorbiterroratregionalscales”,Adv.SpaceRes.,2015,doi:10.1016/j.asr.2014.06.041.
Graz
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SLR–CurrentChallenges:TargetSignature
Jason-1:SLRResidualstoGPSorbitvs.boresightangle
Cerrietal.,2010,MarineGeodesy(Figure5)
Zelenskyetal.,2016,Adv.SpaceRes.(Figure3.2)
SARAL:ArnoldLRAmodelvs.meancorrec-on&datadistribu-onvs
eleva-on
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Summary•TOPEX,Jason-1,Jason-2,Jason-3formaseriesofsatellitesthatprovideessen-alkey“climatedatarecords”tomeasureglobal®ionalsealevelchange.•Thesesatellitesarepartofavirtualconstella-onofal-metersatellitestomonitortheglobaloceantopography.•Alltheal-metersatellitesuseSLRdirectlyforPOD,indirectlyforvalida-on,ortoestablishimprovementinunderlyingmodels.•Challenges:(1) MaintainingstabilityandaccuracyofSLRdata–aswellasminimizingbiases–
orbitRMSradialaccuracygoalis1cmradialRMS.(2) Targetsignaturesonal+metersatellites.(3) Con+nuingtoImprovingmodelsforGeocenter,Non-conserva+veforce
modellingandcoherencebetweenthedifferenttechniquesasmanifestedintheorbitscomputedwiththedifferentgeode+cdatatypesforanygivenal+metersatellite.