Post on 24-Aug-2020
FromTimeTransferbyLaserrangingtoSpaceGeodeticProducts
ILRS-Riga-Latvia-2017-TechnicalWorkshop:AlexandreBellietal.« From TimeTransferbyLaserRanging tospace Geodetic products » 1
AlexandreBelli,PierreExertier,Erricos C.Pavlis andFrankG.LemoineGéoazur,France;BaltimoreUniversity,NasaGSFC;USA
belli@geoazur.unice.fr
Goalsofthepresentation
ILRS-Riga-Latvia-2017-TechnicalWorkshop:AlexandreBellietal.« From TimeTransferbyLaserRanging tospace Geodetic products » 2
WededicatedawholenewmethodinordertodetermineTimeBiasesinLaserRangingstations
WeusedtheTimeTransferbyLaserLink(T2L2)experimentfor8yearsMaingoals:
• Synchronizethewholenetworkat+/- 100nsfromtheUTC(ILRSrecommendations)
Pearlman, M., et al. 2002. The international laser ranging service. Advances in Space Research
• Haveanetworkaccurateat1mmandstableat0.1mm/yrPlag, H.-P. and Pearlman, M. 2009. Global geodetic observing system Meeting the requirements of a global society on a changing planet in 2020. Springer Science & Business Media.
TheeffectofTimeBiasongeodeticproducts(orbit,coordinates)?
TheTimeTransferbyLaserLink(T2L2)experiment
ILRS-Riga-Latvia-2017-TechnicalWorkshop:AlexandreBellietal.« From TimeTransferbyLaserRanging tospace Geodetic products » 33
T2L2+LRATimeTransferbyLaserLink
Jason-2,oceanographicsatellite:• Launchedthe06/20/2008• Atanaltitudeof1336km• Orbitof66°• Orbitalperiod~110min
Passengers :• LPT• CARMEN-2Bezerra,Fetal.2011.Carmen2/mex :Anin-flightlaboratoryfortheobservationofradiationeffectsonelectronicdevices.InRadiationandItsEffectsonComponentsandSystems(RADECS).
• T2L2Samain,E.,etal.2008. Timetransferbylaserlink–thet2l2experimentonjason-2andfurtherexperiments.InternationalJournalofModernPhysicsD.
T2L2offeredatimecolocationon-boardandwiththegroundnetwork(SLRstations).
CommonViewandNoncommonviewTimeTransfer
ILRS-Riga-Latvia-2017-TechnicalWorkshop:AlexandreBellietal.« FromTimeTransferbyLaserRangingtospaceGeodeticproducts » 4
CommonViewTimeTransfer Non-CommonViewTimeTransfer
Basedontheintegrationofanon-boardmodelfortheoscillator(whenT2L2isnotobserved)Accuracy+/- 15nsto5ns(usingGrasseasmasterstation)ComparedtoGPSat0.2nsSamain E.,etal.,2017,(submitted),TimeTransferbyLaserLink(T2L2)innoncommonviewbetweenEuropeandChina.
Accuracyat150psExertier,P.,etal.2014.Timetransfer bylaserlink:dataanalysis andvalidationtotheps level.Advances inSpace Research,54(11),2371-2385.
Stabilityat~ps @75sExertier,P.,etal.2010.Status ofthet2l2/jason2experiment.Advances inSpace Research.DORIS:Precise Orbit Determination andApplicationstoEarth Sciences.
Theon-boardoscillatorstabilityshouldbetakeintoaccountTheon-boardoscillatorstabilitycouldbeneglected
GroundtechnologiesandTimeBiases
ILRS-Riga-Latvia-2017-TechnicalWorkshop:AlexandreBellietal.« From TimeTransferbyLaserRanging tospace Geodetic products » 5
𝐸 𝑡 # = 𝑈𝑇𝐶 𝑡 + 𝑇𝐵#
GPSreceiver
Crossaxis
Lasercalibration
SLRstation
T&Flabo.
clockCables
T&Freferencepoint
Grasse masterstationà TBmonitored+/- 5nsUTC
Weneedareference(AstationlinkedtoUTC/TAI)Samain,E.,etal.2015.Timetransferbylaserlink:acompleteanalysisoftheuncertaintybudget.Metrologia.
Laas-Bourez,etal.2013.Timeandfrequencydistributionimprovementincalern/geoazur laboratoryfort2l2campaigns.InEuropeanFrequencyandTimeForumInternationalFrequencyControlSymposium(EFTF/IFC).
TimeBiasincluded:• Stabilityoftheclock• Calibration(antenna,cables…)• Eventtimer(ns,ps resolution)• Manualoperation,changes…
Method,resultsfor2013andimpactongeodeticproducts(P.O.D,stationcoordinates)
ILRS-Riga-Latvia-2017-TechnicalWorkshop:AlexandreBellietal.« From TimeTransferbyLaserRanging tospace Geodetic products » 6
TimeBiases:Overviewandremarks
ILRS-Riga-Latvia-2017-TechnicalWorkshop:AlexandreBellietal.« From TimeTransferbyLaserRanging tospace Geodetic products » 7
Involved Stationsid:Toperform T2L2calculation,weneedfullratedata!
1888 7124 7821 7941 1884
1889 7403 7822 8834
1890 7406 7824 1886 2016-2017
1891 7501 7825 1824 2008-2017
7407 7237 7848 1831 2009-2017
7080 7308 7832 1873 2012-2017
7090 7358 7838 1873 2008-2011
7105 7394 7840 1893 2011(5mths)
7110 7810 7841 1868 2010-2011(5mths)
7119 7811 7845 1874 2010-2017
Grasse(Masterstation)
ILRS-Riga-Latvia-2017-TechnicalWorkshop:AlexandreBellietal.« From TimeTransferbyLaserRanging tospace Geodetic products » 8
FreeH-maserrunning
Cables change
ILRSrecomm.
Herstmonceux
ILRS-Riga-Latvia-2017-TechnicalWorkshop:AlexandreBellietal.« From TimeTransferbyLaserRanging tospace Geodetic products » 9
Cables change
ILRSrecomm.
Greenbelt
ILRS-Riga-Latvia-2017-TechnicalWorkshop:AlexandreBellietal.« From TimeTransferbyLaserRanging tospace Geodetic products » 10
ILRSrecomm.
Yarragadee
ILRS-Riga-Latvia-2017-TechnicalWorkshop:AlexandreBellietal.« From TimeTransferbyLaserRanging tospace Geodetic products » 11
ILRSrecomm.
Manualoperation??
Freerunningoscillator ??
Changchun
ILRS-Riga-Latvia-2017-TechnicalWorkshop:AlexandreBellietal.« From TimeTransferbyLaserRanging tospace Geodetic products » 12
ILRSrecomm.
Hartebeesthoek
ILRS-Riga-Latvia-2017-TechnicalWorkshop:AlexandreBellietal.« From TimeTransferbyLaserRanging tospace Geodetic products » 13
ILRSrecomm.
+6microseconds
Wettzell
ILRS-Riga-Latvia-2017-TechnicalWorkshop:AlexandreBellietal.« FromeTimeTransferbyLaserRanging tospace Geodetic products » 14
ILRSrecomm.
On-linewebsite !
ILRS-Riga-Latvia-2017-TechnicalWorkshop:AlexandreBellietal.« From TimeTransferbyLaserRanging tospace Geodetic products » 15
http://www.geoazur.fr/t2l2/en/data/v4/
HowtodealwithTimeBiases ?
ILRS-Riga-Latvia-2017-TechnicalWorkshop:AlexandreBellietal.« From TimeTransferbyLaserRanging tospace Geodetic products » 16
• Stationsneedtodoacompletecalibration,whichincludecables,timedistribution,antenna(GPSDO)…
• Controlthestabilityoftheclock,avoidfreerunningoscillators• Haveaneventtimerwithagoodresolution• TimeBiasesneedtobefollowcontinuously• Everychangesonthetechnologyshouldbenoticed,anychangewillleadtoaninevitableTimeBias
Effectsongeodeticproducts
ILRS-Riga-Latvia-2017-TechnicalWorkshop:AlexandreBellietal.« From TimeTransferbyLaserRanging tospace Geodetic products » 17
Workinprogress.
EffectofTimeBiasesontheJason-2POD.
Effectsongeodeticproducts
ILRS-Riga-Latvia-2017-TechnicalWorkshop:AlexandreBellietal.« From TimeTransferbyLaserRanging tospace Geodetic products » 18
P.O.D (along-trackcomponent)ForJason-2(1336km)
Est-West componentforlaserstation(uni-satellitesolution)
DORISTimeBiasimprovement(accuracy)
Severalmm 2-3micros=6mm 1microseconds
Severalstudiesinprogress,seeOSTST2017andAGUFallmeeting2017
Keepinmind:
MicrosecondsTimeBiasleadtommeffectsongeodeticproducts
Conclusions
ILRS-Riga-Latvia-2017-TechnicalWorkshop:AlexandreBellietal.« From TimeTransferbyLaserRanging tospace Geodetic products » 19
• WedevelopacompletenewmethodthanksT2L2todeterminetimebias• Thismethodisdirectandindependentoftheorbit calculation• Firstdemonstrationofopticaltimetransferinnoncommonview(intercontinental)atthelevelof5ns
• For~30laserstations,8yearsofdataavailable,willbeincludedinDataHandlingFiles
• Accuracyat+/- 15ns• ComparedtoGPSatalevelof0.2ns (2016Campaign)• Nonnegligibleeffectsonorbitcomponentsandonthestationcoordinates
Thank you foryour attention!belli@geoazur.unice.fr
http://www.geoazur.fr/t2l2/en/data/v4/