PlutoOcculta*onwithSOFIAon29June2015inSupportofNewHorizonsFlyBy:Occulta*on

EvidenceforHazeEricBecklinforAmandaBoshetalincluding:MikePerson(MITteam),TedDunham(LowellObsteam),JuergenWolf(DSIteam),RyanHamilton,BillVacca,Maureen

Savage,IanMcLean,SarahLogsdon,(FliteCamteam)andtheen*reSOFIAteam

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Outline

•  Background

•  The29June2015data.

•  WhatitmeansforPlutoanditsatmosphere

•  Someproblemsthatneededtobesolved

•  Summary

•  Aspecialthanks

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Background

•  When a Star goes behind a Planet (Occultation), we can learn about the Atmosphere of the planet by measuring how the radiation disappears and reappears.

•  On SOFIA the FLITECAM camera, HIPO occultation camera and the Focal Plane Camera (FPI+) can operate simultaneously by use of dichroic beam splitters.

•  Made Simultaneous observations at 4 wavelengths of Pluto Occultation of 29 June 2015 from New Zealand

•  Highest Priority request from the New Horizons team was 2 micron observations including a central flash

•  I was lucky enough to be on the flight.

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Occultations can best be done from a Flying Observatory

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Pluto Occultation on 29 June 2015

•  Occultation of 12-mag star by Pluto on 2015 June 29 in support of New Horizons.

•  Goal was to be within 25 km of center of Pluto shadow of 2400 km. (1 milli-arcsec and 100 milli-arcsec)

•  Ground shadow moves 90,000 Km/hr. Plane 900 Km/hr.

•  Final ground-based shadow updates required course adjustments of 200 km (8 milli-arcsec) –  Updates to shadow path kept

coming even after the plane took off.

–  Mobility of SOFIA was key to getting the observation

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PlutoandOcc.Starat1.8microns5hrsbeforetheOcculta*on

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FliteCamteamduringOcculta*on

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Ted,Mike&RyanduringPlutoFlight

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•  Detection of strong “central flash” confirms accuracy of course corrections (within ~20 Km of Pluto center)

•  Light curves show effect of mostly refraction in a thin atmosphere.

•  Stability of Pluto’s atmosphere over last 25 years determined.

•  Comparison of multi-wavelength observations allows detailed analysis of atmospheric profiles and aerosol or haze content.

Science Highlight: Pluto Occultation

Li]leornochangeinlast25yearsofPlutoAtmosphere

•  PlutoismovingawayfromtheSun

•  Somepeoplesuggestedachangemightoccur(ieatmospherewoulddecay)

•  Li]leevidencefromOcculta*ondataforanychangeover~15years.Somechangeearlier,densitywas~2*meshigher.

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Comparisonwithearlierresults

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CentralFlashandDepthSuggestPar*cleHazeisPresent

•  Noatmospherewouldproduceasquareocculta*on

•  AClearatmospherewouldproducelargecentralflashandextraemissionatthebo]omofthelightcurve.

•  Therefrac*onstartsat10to20Kmabovethesurfaceoutsidethesurfaceoftheplanet.

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HIPO-blueClearatmwithdT/dz

HazeplusdT/dz

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TheBluetoInfraredcurvesshowthepresentsofdustorhaze

•  Bluecurveshowssmallestexcessemissionatthebo]om(cloudyornotclear)

•  Infraredshowsthehighestexcessemission(clearestatmospherebecauseIRseesthroughthedust)

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Lightcurveminimumflux

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Summaryofcolordata

•  1.8microndatashowtheleasteffectofdustinthelightcurves(rela*velylowcentralflashisduetolongintegra*on*me)

•  Similartrendwasshownin2002fromHawaiiMKOdata(Elliotetal2002)

•  AmountofdustneededissimilartohazeseenbyNH•  Amodelwithoutdust,usingtemperatureandpressuregradients,resultsinaPlutoradiussmallerthanthatmeasuredbyNHby50km.Alsodoesnotexplainthe1.8microndata.

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SomeProblemsthatneededtobesolved

•  Posi*onupdateofPlutoandtheocculta*onstar.

•  Theaircrafdamagethedayoftheocculta*on.

•  Theweatherandwheretoland.•  TwoproblemswithFliteCam(Electronicsandextrabackgroundfromengineemission)

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ThePosi*onUpdates

•  Posi*onupdateskeptcomingevenaferwetookoff.

•  Measurementswerebeingmadefromaroundtheworld(Chile,Arizona)andanalyzedatMIT

•  Changedtheflightpathby200km(MostlyduetoPlutobrightspot)

•  Workedouthowtodothenaviga*onontheprac*ceflightthenightbefore.

•  Correc*onshandoffhadacoordinateissuewhichgotsolved.

•  Hitthetargetwithin20Km(0.001arcsecand~3secof*me)

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DamagetotheAircraf

•  Ontheafernoonofthedayoftheocculta*ontheAircrafwasdamagedbythebo]ombarofthebackflapofthecryogentruck.

•  Windgustknockedoutawindowandputa~2inchdentintheskin.

•  TheSOFIAmaintenanceteamwiththehelpofAirNewZealandmadetherepairandclearedcer*fica*onbeforetakeoff.

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Weatherandwheretoland

•  Thiswasanissueastheposi*ongotupdated.•  Themostcri*calwastheprac*ceflightthenightbefore.

•  LandinganywhereotherthanChristchurchwouldnotallowacryogenfill.

•  Anearlytakeoffandlandingwithashortflight(~4hr)gaveusthebestchancetoavoidfog,whichisquitecommoninChristchurch(~5-10%)

•  Wedidnotcarewherewelandedontheocculta*onflight

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IssueswithFliteCam(electronics)

•  FliteCamwasshippeddowntoNewZealandwithknownintermi]entissueswiththearraydriveelectronics.

•  WhenFliteCamwaspoweredupthearraydriveelectronicsdidnotwork.

•  Luckily,theIRTFhadsentustheredriveelectronicsasaback-up.

•  3daysbeforetheOcculta*ontheFliteCamteam(ChrisJohnson,UCLA)transferredtheIRTFspearandgotitworking

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IssueswithFliteCam(ExtrabackgroundfromEngineemission)

•  Ontheprac*ceflightweno*cedextrabackgroundat2.1micronsthatwasvariableastheplane*ppedanddependedontelescopeeleva*on.

•  Reducethesignaltonoisebygreaterthanfactorof3.•  Thiseffecthadbeenno*cedinthecommissioning,butwasnotfully

characterized.•  IcalledBillVacca,andhesuggestedusingtheH(wide)blocker

whichhadacentralwavelengthof1.8microns.•  Observa*onsonthePlutofieldwiththisfilterweremadeatthe

beginningoftheOcculta*onflight.RyanHamiltonquicklyreducedthedataanditshowedthesamenoiseasK,butover2*mesbe]ersignalontheOcc.star.

•  FromPlutoatmosphericmodelswealsoknewthatthePlutosignaltonoisewasprobablyevenafurther30%larger.

•  ThePIMikePersondecidedwewouldusethe1.8micronfilter.

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IssueswithFliteCam(backgroundandstar*ngtosolve

whereiswascomingfrom)•  The200kmposi*onchangewasnorthwhichmadethe

eleva*onhigherandreducedtheextrabackground,butitwass*llthere.

•  RyanHamiltonsuggestedweputthepupilviewingmodeinaferweobtainedthedata.Weallagreed.

•  ResultsareshownonthenextslidewithacomparisontoanearlierstudybyBreault(BRO).

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ComparisonofBreault(BRO)Calcula*onsandPupilPlaneimages

•  EmissiononthetopofPrimaryPredicted

CourtesyofP.Waddell

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FliteCamBackground

•  At40degeleva*ontheextrabackgroundwascomingfromtheafspider

•  WorkbyPatrickWaddellandBillVacca,showedthatitwasprobablyhot(T~600to700K)emissioncomingfromtheafoutboardengine(#1)onthelefsidereflectedofftheunfinishedbo]omofthespidervain.

•  Bafflesarenowbeingpreparedtoeliminatethereflec*on.

•  PatrickWaddellmayspeakaboutthisonalaterteletalk.

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Summary

•  SOFIAhasprovideddataonPlutothroughanOcculta*ontwoweeksbeforeTheNewHorizonflybythatcanbeusedtohelpmonitorPluto’satmosphereforyearstocome.

•  SOFIAcandogreatscienceandcarryoutuniqueexperiments

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SpecialThankYou

•  SOFIAwouldnothavebeenpossiblewithoutyearsof*relessworkandgeniusofHans-PeterRoeser(DSIStu]gart)andNansKunz(NASAAmes)

•  BothstartedworkingonSOFIAinthe1980’s

•  Bothpassedwaywithinthelastyear27

Backup

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Results AtmosphericchangeAtmospherichaze

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