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DORISUSOBehaviorRevealedbyJason-2/T2L2F.G.Lemoine,P.Exer)er,A.Belli,N.Zelensky

IERSUnifiedAnalysisWorkshopUniversitéParis-Diderot

Paris,FRANCEJuly10-12,2017

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DORISSystemDescripAon

DORISSatelliteAntenna

DORISOven-controlledUSO

DORISSystemConfiguraAon

AuriolandTourain,Adv.SpaceRes.,(2010)

USOCharacterisAcs:•HeartofDORISsystemisUSO.•AccuracyofphasemeasurementsdeterminedbystabilityofUSO.•USOisacrystal-oscillatorthatispre-hardenedtoreducesensiAvitytoradiaAon(e.g.Jason-2,Jason-3).•DORISUSO’shaveasensiAvitytoradiaAonexposurethroughpassageintheSouthAtlanAcAnomaly.Jasonsatellitesmoreaffected@1336km);Discernibleonothersatellites(SPOT-5,@~800km).

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DORIS/USO–PreviousExperiences

SPOT-5FreqDri_from2011,Hz/day

Willisetal,CRGeoscience.(2004)

1.Anomalousfrequency(Δf/f)leadstoanomalousheightesAmaAonforstaAonsinheartofSAA.2.ForstaAonsonborder,behavioriscomplicatedbecauseascendingordescendingpassesaremoreaffected.3.AcorrecAonmodel(JMLemoine&Capdeville,2006)allowsdatatobeusedforPOD.Notsuitableforpos-vel.esAmaAon(SAAstaAons).

DORISTOPEXvs.Jason-1FrequencyAnomalies,Apr.2003

Stepaneketal.Adv.SpaceRes.(2013)

1.SPOT-5SAAeffectundetectedunAlpointedoutbyStepaneketal.(2010).2.SmallerthanJason-1,butsAllnoAceableeffect;Importanta_er2006.3.StaAonsinandnearSAAaremostperturbed;e.g.CADB,ARFB,SANB,KRWB,HEMB,ASEB.4.CorrecAvemodelusedforITRF2014.Capdevilleetal.(2016).

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RadiaAonExposure(fromCNESEngineeringtables)

Jason-2,3:~2500rads/yr

SPOT-4,5,SARAL,ENVISAT:~360rads/yr

ImpactonDORIS/ITRF2014

SAAOn-boardFreqsignalover5-days,Jason-1,SPOT-5,SPOT-4

Capdevilleetal.Adv.SpaceRes.(2016)

1.  ITRF2008staAonposiAons&velociAesfor“SAA”staAonsdirectlyaffectedbyuncorrectedSPOT-5data.

2.  ForITRF2014:AllACsusedcorrecAvemodeland/ordownweighAngeliminaAonofSAAstaAondataforSPOT-5&Jason-1.

SatellitedatausedinITRF2008/ITRF2014

Moreauxetal.Adv.SpaceRes.(2016)

Jason-1:Onlyincludedata11/2004-07/2008

SPOT5:Usecorrecteddata,2006-2015

1.  Jason-1includedsinceitsinclinaAoncomplementstheothersatellites.

2.  Use“correcteddata”+downwt/eliminateSAAstaAons.

3.  NoothersatelliteUSOsreceivespecialtreatmentinITRF2014.

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Jason-2/T2L2

ExerAeretal.Adv.SpaceRes.(2010)

1.  “TimeTransferbyLaserLink”2.  Twophotondetectors+eventAmer

withpsresoluAonlinkedtotheDORISUSO.

T2L2recordsinAmescaleprovidedbyDORISthearrivalAmeoflaserpulsesatJason-2.IncombinaAonwithprecisegroundclocksatSLRstaAons(H2masers),itispossibletodetermineΔf/foverAmeintervalsofT=60secs.PrecisionisdependentonshorttermstabilityofUSO,quanAty&qualityofrangemeasurements.3-5x10-13

Jason-2

LaserRetroreflectorArray

Jaylesetal.Adv.SpaceRes.(2016)

TwoApplicaAons:(1)“Synchronize”TimingofSLRnetwork.(2)StudyindetailbehaviorofUSOinspaceenvironmentandcharacterizedifferenteffects(radiaAon,thermaleffects,aging).

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T2L2Data:Example

Bellietal.Adv.SpaceRes.(2016)

1.  BestdatacomesfromstaAonswithH2masers:Grasse(7845),Herstmonceux(7840).

2.  DatacanreadvariaAonscausedbyradiaAondosage(SAA),temperaturevariaAons,andaging.

3.  Thedatabenefittwotechniques:bothDORIS&SLRgivingusanunderstandingandglobalperspecAve.

Δf/finJan.2013fromfiveSLRstaAons.

SeealsoA.Belli,PhDThesis(2017)

USOEffects&ModelDerivaAon

Bellietal.Adv.SpaceRes.(2016)

SeealsoA.Belli,PhDThesis(2017)

TemperatureEffectsonJason-2USOJan.2013,showingorbit-to-orbiteffects&impactofchangeinJason-2aqtude.

Jason-2CARMEN87MeVintegratedprotonfluxmap(2009–2011average).

Capdevilleetal.Adv.SpaceRes.(2016)

RadiaAonModel

Dri_Model

Jason-2USOModel&Comparisonw.T2L2

Bellietal.Adv.SpaceRes.(2016)

RadiaAonModelover~1.5-daysforJason-2showingeffectsofSAApassage.

Bellietal.Adv.SpaceRes.(2016),Fig4

Jason-2FrequencyvariaAonsfromTemperatureandRadiaAon:ModelvsT2L2data.

USOEffects&ModelRefinementforJason-2&Jason-3

TemperatureEffects •Sufficienttocalculateonlyrateterm:

α1[T(t)–To]•CoefficientsforJ2(2008),J3(2016)similarmagnitudebutoppositesign.

RadiaAonEffect@60-days

•A60-daysignalwasobservedintheT2L2datawhenthes/cisinfixedyaw.Increaseovertendays,thenrelaxaAonover45-50days.•Bellietal.(2017)proposethisisduetoalignmentofYaxisofs/cwithmagneAcfieldlines,leadingtoincreasedsensiAvitytoradiaAoninSAAareainfixed-yawregime.•Itispossibletosolveexplicitlyforcoefficientstomodelthisbehavior.•ThesignificanceisthatBellietal.(2017)haveidenAfiedanaddiAonalsignalataJason-sub-draconiAcperiod(~60days)thatisinthecurrentdata,andisnotdrivenbyradiaAonpressuremismodeling.***

Bellietal.,EuropeanFrequency&TimeForum(2017)proceedingpaper

***AC’smustsAllimproveSRPmodel,includemoAonofsolararraysusingquaternions.

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Data used: MOE SLR stations (T2L2) Temperature of the box => df/f0 with 1.85 10-12 /degree

CNES POD (MOE) can “read” USO for H2 maser (time, frequency) beacons ‒ since freq. biases (range-rate) biases estimated per pass. Sees freq. variations with precision of ~1-1.2 x 10-12

compared to ~3 x 10-13 for T2L2

Jason-2USOBehaviorvs.CNESMOEFreq.biases

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DORIS USO (frequency bias): long term

Frequency variations of J3 are >> J2 in 2016 but not in 2008

RelaAvefrequencyvariaAons2015-2016Jason-2freqvariaAons2008vs2016RadiaAonsensiAvityhasdecreasedwithAme.

13Bellietal.IDSWorkshop(2016)

Here,MOEΔf/farefilteredwith1-dayfiltertoeliminatemedium&long-termsignalJason-2Δf/f(2008)(TOP)vsJason-3Δf/f(2016)(BOTTOM)fromMOEsoluZons.Jason-3sensiAvitytoradiaAonisabout~3XthatofJason-2atthesameageofspaceexposure.

Jason-2 vs Jason-3 Sensitivity

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Summary

DORISUSOSensiAvitySummary1.  USOsshowsensiAvitytotemperature,radiaAon,andhaveagingeffects.2.  A“60-day”effectonDORIS-USOisidenAfiedthatisrelatedtoJasonaqtude

lawandanisotropyofincidentradiaAonfluxintotheUSObox.3.  SensiAvityisaffectedby“pre-treatment”andamountofshieldingons/c.4.  Ageneralmodelthataccountsparametricallyfortheseeffectscanbe

derivedforJason-2andeventuallyforJason-3.5.  Lowersatellites(SPOT-5)notimmune.Suggeststhereisaneedforgeneral

treatmentoftheseeffectsonallDORISsatellites.

ImmediateFutureAcAons1.  PIerreExerAer/A.BellitomakeavailablecorrectedDORIS/V2Data(Jason-2)

fortesAngbytheDORISAnalysisCenters.2.  ImprovedFrequencymodelofJason-2&Jason-3canbeimplementedin

DORIS/RINEXprocessing–tobetestedbyNASAGSFCandotherDORISACs.