UpdateonGNSSPerformanceMonitoring

YoazBar-Sever(Yoaz.Bar-Sever@jpl.nasa.gov)

JetPropulsionLaboratoryCaliforniaInstituteofTechnology

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15YearsofJPLGPSPerformanceMonitoringfortheAirForce

InitiatedbyAerospaceCorporationfollowingtheSVN22eventofNovember5,2002

TheJPLGPSperformancemonitoringservicewasjointlydevelopedbyJPLandAerospace,withinputfromthe2SOPSoperators• Fundedinrecentyearsby2SOPSoperationalbudget• Continuouslyrefinedandaugmentedwithadditionalcapabilities• Usetrackingdatafrom80+sitesintheGlobalDifferentialGPS(GDGPS)network• GDGPSreal-timeorbitandclocksolutionsareusedasTruth

Monitorkeyperformancemetricsofthebroadcastephemerisandthenavigationsignals• Userrangeaccuracy,duetobroadcastorrangingsignal• Correctnessofkeybroadcastparameters• Satelliteobservabilityassessment• 30secondlatency

GPS-basedarrival-timesystemonatraintraversingtheEasternseaboardsawextraordinarypositionerrors.

Source:J.Langer,Aerospace,April2003

TheactiveRubidiumclockontheBlockIIAspacecraftexperiencedafrequencyjumpwhilethesatellitewasnotmonitoredbytheOCSfornearly2hours

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SnapshotoftheGDGPSCNAVMonitoringWebPage

Recently-addedcapabilities:• CNAVmonitoringonL2andL5• UTCmodel(aftertheJan2016event)

• DifferentialCodeBiasesmonitoring• GNSStimetransferparameters(in2018)

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SnapshotoftheGDGPSCNAVMonitoringWebPage(contd.)

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MonitoringinSupportofSingle-FrequencyUsers

LeveragingJPL’sionosphericexpertiseanddenseglobalnetwork

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MonitoringandUploadofInter-FrequencyBiases

-25.00

-20.00

-15.00

-10.00

-5.00

0.00

5.00

10.00

10 20 30 40 50 60 70 80

Tgd

(ns)

SVN

Three Tgd EstimatesJPL Tgd Estimate 2017/04 (ns)JPL Tgd Estimate 2017/01 (ns)Previous JPL Tgd Estimate 2016/10 (ns)

JPL’sTgd estimatesarebeingbroadcastbyGPS;Updatedquarterlyandonchange

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TheFoundation:ExtremelyRedundantGlobalReal-TimeTrackingNetwork

80+globaltrackingsitesdeployed,controlled,operated,andmaintainedbyJPL’sGDGPSSystem• HardwareandsoftwarefullyownedandcontrolledbyJPL• Decadesofsitestability,quality,andcontinuity• 25-foldobservationredundancy,onaverage,enablestrongmajorityvotingschemes

Hundredsofcontributedsitesoperatedbyavarietyofpartners,U.S.andforeignagencies(e.g.,NSF,BKG,GA)provideadditionallevelofredundancyanddensityofcoverage

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CSM,OnceAgainJPLalreadymonitorsandreportsallthekeynavigationmetricsoftheGPScivilsignals

JPLalreadypossessesallthedataneededtoverify90%oftheCivilMonitoringPerformanceSpecifications(CMPS)

JPLproposedtomonitor98%oftheCMPSwithinayear• LeveragingthesignificantNASAandUSAFinvestmentintheGDGPSSystem• PNTABrecommendedusingthecost-effectiveGDGPSsystemforCSM(Parkinson,2013)• TheproposalwasanalyzedbytheFAA2014CSMTradeStudyTeamandfoundattractive

Refinedproposal(workedwithFAA)submittedtoFAAinOctober2015.Thensilence.

WecouldhavehadCSM15yearsago!

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Real-TimeGNSSPerformanceMonitoringAvailablenowGDGPSismonitoringthecivilsignalsfromGLONASS,BeiDou,andGalileo.Soon,QZSS• IRNSSmonitoringisbeingassessed• 100%redundantglobalcoverage

HighaccuracyrealtimeorbitandclocksolutionsprovidesomebenefitsrelativetoGPS-onlyincertainapplications• e.g.Earthquakemonitoring:

GDGPS Real-Time Natural Hazard Monitoring

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Displacementmonitoringfor200+sitesathttps://ga.gdgps.net

Real-TimedetectionoftsunamiionosphericdisturbanceswithGNSSgroundtracking(Savastano etal.,Nature,2017)

ConclusionsExistingandprovenGDGPStrackingnetworks,technologies,andoperationalcapabilitiescanprovideeffectiveandlowcostGPScivilsignalmonitoring

JPL’sGDGPSSystemalreadytracksandmonitorsGLONASS,BeiDou,andGalileoonaglobalscale• CanbeusedtoalleviateconcernsintheU.S.aboutincorporatingGNSSsignalsintocertain

regulatedservices,suchasE-911geolocation• ThesystemisalreadybeingusedcommerciallytoprovideAssistedGNSSservicestomillions

ofmobileusers

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Prototypesystemandtestbed forNextGenerationGPSControlSegment(OCX)

Triple Hot Redundant Operation CentersReal-Time Tracking Network

(200+ sites)

Measurements Products, Services

The Global Differential GPS (GDGPS) SystemProviding mission-critical, real-time services, 24/7, since 2000

FullGNSScapabilities:GPS,GLONASS,BeiDou,Galileo

PersonalGeolocation

PrecisionIndustrialPositioning

GNSSMonitoring

Time-criticalenvironmentalmonitoringservices

Space weather monitoring

Repeat path interferometry with UAV-SAR

GNSS navigation data for Radio Occultations

Earthquake monitoring and tsunami prediction

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