SpaceNaviga+onusingX‐rayPulsarObserva+ons

J.Hanson,CrossTracEngineering,Inc(408)898‐0376

hanson@netwiz.net

X‐rayNaviga+on(XNAV)

•  X‐rayPulsarsasGuideStars•  BriefHistoryofXNAV•  X‐rayPulsarsforPosi+onDetermina+on

•  X‐rayPulsarsasPrecisionTimeReferences

•  AWtudeDetermina+onUsingX‐raySources

•  XNAVDemonstra+onMissions

•  Acknowledgements

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XNAVSources:X‐rayPulsars

•  Theprincipalceles+alsourcesconsideredareX‐raypulsars

–  Rota+on‐poweredPulsars(RPSR)

–  Accre+on‐poweredmilli‐SecondPulsars(MSP)

•  Alternatesourcesarealsobeingexplored

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•  Pulsarsprovidestablefrequencystandards•  Varianceofmillisecondpulsars(mostpreciseastronomicalclocks)is

comparabletothatofatomicclocks

XNAVSources:MSPsasCeles+alAtomicClocks

Pulsars Atomic Clocks

Matsakis,Taylor,Eubanks,A&A,1997Kaspi,Taylor,&Ryba,ApJ,1994

X‐rayGuideStars

•  Verydifferentfromthe“visible”sky

•  Nearlyallsourcesextendedorvariable

XNAV–ABriefHistory

•  1967:BellJ.&HewishA.Successfuldiscoveryofradiopulsar•  1974:Downs,G.S.fromNASA/JPLoutlinesconcept,“InterplanetaryNaviga+onUsing

Pulsa+ngRadioSources”•  1981:Chester&ButmanalsofromNASA,“Naviga+onUsingX‐rayPulsars”•  1988:WallaceK.fromU.K.useofradiostarsfornaviga+onalsystems•  1988:KentWoodofNRLproposestheUnconven+onalStellarAspect(USA)experimentto

DoD(OperatedMay1999‐Nov2000)

•  1996:Hanson,J.E.StanfordPh.D.disserta+on“PrinciplesofX‐rayNaviga+on”

•  2004:ESAAdvancedConceptsTeamARIADNApulsarnaviga+onstudy

•  2005:Sheikh,S.I.UMDPh.D.disserta+on“TheUseofVariableX‐raySourcesforSpacecrajNaviga+on”

•  2005‐2006:DARPAXNAVPhaseIProgram

•  2006‐Present:NASASupportsXNAVdevelopmentthroughseriesofSBIR’swithMicrocosm/CrossTrac/ASTER

•  2010–DARPAWhitePaperonXTIMConceptandApplica+ons

•  2010–DARPAbeginsinstrumentdevelopmentforXTIMdemonstra+onmission

•  2011–SEXTANTSelectedforPhaseAstudywithstrongsupportfromNASA/OCT

XNAVConcept

•  Pulsarsignalscanbeusedasanaturalnaviga+onreference•  Theyprovideanoscilla+ngsignalwithlong‐termstabilitycomparabletoatomicclocks•  XNAVconceptessen+allycomputesarangefromtheSSBtoaspacecrajalongthe

direc+onfromtheSSBtothepulsar•  Conceptusesrangeandrange‐rateforaccurateposi+onandvelocitysolu+ons

–  However,lineofsightaWtudemeasurementsfromthesesourcesalsoavailable

–  So,occulta+onandpulsar‐eleva+onmeasurementsalsopossible•  TherearemanyalgorithmicanalogiesbetweenXNAVandGNSSsystems

XNAVInstrument

•  Withstoredaccuratesource+mingmodelsandsufficientcollec+on+meanddetectorarea,pulsarsignalscanbefilteredtoproduceaccuraterange,range‐rate,andpoten+ally+mees+matesforspacecrajinEarthorbitorinterplanetaryspace

•  X‐rayemiWngpulsarsignalsarefaint,noisy,andnottaggedwith+meorECIposi+onoforigin

•  Poten+alApplica+ons–  AutonomousSpacecrajNaviga+on–  DSNAugmenta+on–  ClockSynchroniza+on

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XNAVPerformance:B1821‐24

Pulse Period 3.05 msec

Avg Pulsar Flux 6.04·10-4 ph·cm-2·sec-2

Pulse Fraction 0.98

Bin Size 0.1 µsec

Diffuse X-ray Bkgnd Flux 0.1 ph·cm-2·sec-2

Net Cosmic Ray Bkgnd Flux 5 ph·cm-2·sec-2

Detector Bkgnd Rate 0.1 ph·sec-2

•  HistogramofB1821‐24pulseprovidedbyPaulRay(NRL)

•  Doublegaussianpulsemodelfittosimulateddata

•  Deriva+vescalculatedanaly+cally

•  Integralsevaluatednumerically

PredictedPerformance:B1821‐24

XNAVApplica+ons

•  Earth‐SunL2Point-  Autonomousnaviga+onandorbitmaintenance

•  OuterPlanetsandDeepSolarSystem-  Accuracy(normaltolineofsight)couldaugmentDSN

atdistances>Jupiter•  PlanetaryApproachesandOrbits-  Improveautonomyandreduceopera+onscostand

DSNload•  Forma+onFlyingandRela+veNaviga+on-  Canuseaperiodicsourcesaswell

•  GPSAugmenta+onandBackup

XTIMConcept

Pulsar1

Pulsar2

X‐rayPulsarsasa“Universal”TimeReference

•  Globallydistributed+mereference– Doesnotrequireline‐of‐sightbetweenreferencespacecrajtosynchronize+me

•  Longdura+onstableabsolutereference– Usedinconjunc+onwithlocalatomicclock

•  “Short”dura+onstablerela+vereference– AllowssourceslikeCrabtobeused

XTIMApplica+ons

•  Numerouspoten+alapplica+onsforXTIM–  Provisionofaccurate+metoasystemofusers–  Supportforsecurecommunica+ons

–  Verifica+on/valida+onofnewclocktechnologies–  Enhancedobserva+ontechniques

•  e.g.DistributedRFCommunica+ons

–  Enhancedstudiesofvariableceles+alsources–  Stabilitymonitoringofexis+ng+mestandards

–  Reliabilityandintegrityofsecurecommunica+ons•  e.g.financialdatatransfer

X‐rayAXtudeDetermina+onPrecisionX‐rayStarCamera

•  Smalldiffrac+onlimitduetoshortX‐raywavelength

•  Milli‐arcsecondcapable•  Poten+alforsmallpackage

X‐rayStarScanner

•  ArcminutelevelaWtudedetermina+on•  Forusewithspinstabilizedspacecraj•  CubeSatcompa+ble

XSSConcept

10cm

•  SimpleX‐raydetectorwithcollimatorlimitsfieldofview

•  Asspacecrajspins,aseriesofpulsesarecreated

•  Eachcorrespondstotheposi+onofastar

•  AWtudesolu+ongeneratedfromuniqueparern

XNAVTechnologyDemonstra+ons

XTIMDemonstra+onXTIMInstrument(DARPA)

•  Willdemonstrateconceptof“locking”toanX‐raypulsar

•  InstrumentCDRinearly2012

XNAVDemonstra+onSEXTANT(GSFC)

•  WilldemonstrateXNAVposi+ondetermina+ononSpaceSta+on

•  Currentlyintechnologydevelopmentphase

Acknowledgements

•  NASA–  RussellCarpenter,KeithGendreau(GSFC)–  CharlesNaudet(JPL)

•  DARPA/IARPA–  DerekTournear

•  NRL–  KentWood,MichaelLovellere,PaulRay

•  UniversityofMaryland–  DarryllPines

•  JHU/APL–  DanielJablonski,RobertGolshan

•  Cateni–  PaulGraven

•  ASTERLabs–  SuneelSheikh