from time transfer by laser ranging to space geodetic products · ilrs recomm. herstmonceux ......

FromTimeTransferbyLaserrangingtoSpaceGeodeticProducts

ILRS-Riga-Latvia-2017-TechnicalWorkshop:AlexandreBellietal.« From TimeTransferbyLaserRanging tospace Geodetic products » 1

AlexandreBelli,PierreExertier,Erricos C.Pavlis andFrankG.LemoineGéoazur,France;BaltimoreUniversity,NasaGSFC;USA

[email protected]

Goalsofthepresentation


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


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


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)


TimeBiases:Overviewandremarks


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)


FreeH-maserrunning

Cables change

ILRSrecomm.

Herstmonceux


Cables change

ILRSrecomm.

Greenbelt


ILRSrecomm.

Yarragadee


ILRSrecomm.

Manualoperation??

Freerunningoscillator ??

Changchun


ILRSrecomm.

Hartebeesthoek


ILRSrecomm.

+6microseconds

Wettzell

ILRS-Riga-Latvia-2017-TechnicalWorkshop:AlexandreBellietal.« FromeTimeTransferbyLaserRanging tospace Geodetic products » 14

ILRSrecomm.

On-linewebsite !


http://www.geoazur.fr/t2l2/en/data/v4/

HowtodealwithTimeBiases ?


• Stationsneedtodoacompletecalibration,whichincludecables,timedistribution,antenna(GPSDO)…

• Controlthestabilityoftheclock,avoidfreerunningoscillators• Haveaneventtimerwithagoodresolution• TimeBiasesneedtobefollowcontinuously• Everychangesonthetechnologyshouldbenoticed,anychangewillleadtoaninevitableTimeBias

Effectsongeodeticproducts


Workinprogress.

EffectofTimeBiasesontheJason-2POD.

Effectsongeodeticproducts


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


• WedevelopacompletenewmethodthanksT2L2todeterminetimebias• Thismethodisdirectandindependentoftheorbit calculation• Firstdemonstrationofopticaltimetransferinnoncommonview(intercontinental)atthelevelof5ns

• For~30laserstations,8yearsofdataavailable,willbeincludedinDataHandlingFiles

• Accuracyat+/- 15ns• ComparedtoGPSatalevelof0.2ns (2016Campaign)• Nonnegligibleeffectsonorbitcomponentsandonthestationcoordinates

Thank you foryour [email protected]

http://www.geoazur.fr/t2l2/en/data/v4/

from time transfer by laser ranging to space geodetic products · ilrs recomm. herstmonceux ......

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