AProbeMissiontoTraceWater
fromInterstellarCloudstothe
SolarSystem
AProposalSubmittedtotheNASAAPROBES2016Call
PaulGoldsmith,PI
JetPropulsionLaboratory,CaliforniaInstituteofTechnology
TedBergin,PerBjerkeli,DominiqueBocklée-Morvan,PaolaCaselli,
Maryvonne Gerin,AntoineGusdorf,DaveLeisawitz,Darek Lis,Gary
Melnick,KarinOberg,JorgePineda,NealTurner,KarenWillacyCo-I’s
TracingWaterfromInterstellarCloudstotheSolarSystem
• UnderstandingtheoriginsofthewaterontheEarthandotherhabitableplanetsrequires
followingthismolecule’strailfrominterstellarcloudstodensecoresinwhichnewstars
form,tothe diskssurroundingtheyoungstarsandinwhichplanetsform,andfinallyto
oursolarsystem.
• Herschelobservationshaverevealedwater’subiquityinalloftheseregions,especiallyin
thesolarsystemwhereitisfoundincomets,asteroids,satellites,aswellasplanetary
atmospheres.
Highspectralresolutionstudiesoftherotationaltransitionsofwaterandits
isotopologues (especiallyHDO)areessentialfortracingwater’sformation,itsroleasa
coolant,itsprocessinginavarietyofenvironments,anditsrelationshiptoicesondust
grainsurfaces.
Thelinkages betweenthesedifferentstagesinthewatertrailhavebeenemphasizedby
recentstudiesaddressingwaterdeliveryfromcorestodisks(Furuya etal.2016,Astron.
Astrophys.Inpress)andfromaprotostellar disktooursolarsystem(Cleeves etal.2014,
Science,345,1590)
FourInterrelatedPhasesoftheWaterTrail
WaterEmissioninOrion
GroundState(557GHz)Emission
DominatedbyBroadOutflow
ExcitedState–
Thermal&MaserEmission
Offset(arcseconds)
Herschel
WaterasTracerofDenseCoreKinematics
Cold(8-12K),compact(0.1pc)dense(103-107 cm-3)
Precursorstonewstars;shouldbecollapsing
Whatisthevelocityfieldincollapsingcores?
Allmodelshave~samen(r)butvastlydifferent v(r)
Keto,
Caselli,
Rawlings
2015
SingularIsothermalSphere
Larson-Penston
UnstableB-ESphere
Water:demandingexcitation=>tracersinnermost,densestregions
C18O:easytoexcite--tracesoverallcoreanditsmotions
L1544H2O557GHzdata
fromHerschelHIFI
Notevelocityresolution
H2O
C18O
Theoretical
Models
Onlythe
QuasiEquilibrium
Bonnor-Ebert
Spheremodel
reproduces
observations
ofL1544
WaterLinestobeObserved
448.0
2264.1
1893.7
2365.9
2196.3
3807.3
1602.2
2074.4
WaterintheInterstellarMedium:
inabsorption:Lowestorthoandpara- transitions
inemission(shocks;outflows)
Lowesttransitions+excitedlinesnear
1100GHz
4512.4
4468.6
1162.9
2640.5
1097.4
2391.6
1919.4
3977.0
1153.1
3331.5
183.3
1228.8
1661.0
1716.8
2774.0
2968.7
2164.1
752.0
987.9
1669.9
556.9
1113.3
WaterinDenseCores:Probably
lowesttransitionsonlywillbe
detectable
WaterinDisks: Arangeoftransitions
ispossible
WaterintheSolarSystem:Lowest
ortho– andpara- transitions;
isotopologuesessential
Transitions of H2O
Freq (GHz) Transition Species
509.3
110 – 101 (HDO)
547.7
110 – 101 (o-18)
552.0
110 – 101 (o-17)
556.9
110 – 101 (o-16)
987.9
202 – 111 (p-16)
994.7
202 – 111 (p-18)
1107.2
111 – 000 (p-17)
1009.9
211 – 101 (HDO)
1113.3
111 – 000 (p-16)
1097.4
312 – 303 (o-16)
1153.1
312 – 221 (o-16)
WaterTransitions
tobeObserved
Detailsdependonbandwidthofreceivers
whichwillbeSISmixers
Frequency-multipliedlocaloscillator
sourceshaveadvancedsignificantlyand
shouldnotbeaproblem
Injectlocaloscillatoreitherthrough
waveguidedirectionalcoupleroremploy
balancedmixers
Somereceiverscancovermorethanone
linewithmultiplesecondlocaloscillators
ReceiverConceptstoIncreaseSensitivity
Polarizing#Grid#
Ellipsoidal#
Mirror#
Ellipsoidal#
Reflector#
FSS#
Band#1#Array#
Beam%from%telescope%
(through#calibraBon#
system)#
Orthogonal#
PolarizaBon#
Directed#to##
2nd#Receiver#
#
FSS#
Band#3#Array#
Band#2#Array#
1. UseDichroicFilters
(FrequencySelective
Surfaces)andoperateall
channelssimultaneously
2. Employanarray(size
dependsonbudget,
cooling,andpower)for
imagingISMandCores
3. Beamswitchbetween
twopixelsfor
observationofsmall
sources(internalmirror)
4. Dualpolarization
receiversforall
frequencies
5. Improvedmaterialsfor1
THzSISjunctions
6. Cooledwithclosed-cycle
refrigeratortoget5yr
lifetime
SpectrometerforHeterodyneReceivers
Thishasbeenanissueatmm/submmwavelengthsbecauseofrequiredlargebandwidthand
multiplicityoflines
Solutionshaveincludedfilterbanks (typicallyusedonatmosphericsounders),chirpspectrometers
(lowpower;usedonplanetarymissions),andacousto-opticalspectrometers(complex,heavy;used
onSWAS(SMEX)andHerschel/HIFI)
Digitalsignalprocessing,offeringmanyadvantages,isnowfeasiblebutFPGAapproachisrelatively
powerhungry(~4W/GHzBW)
IdealtechnologyiscustomVLSIusingtechnologydevelopedforcellphonesandother
communicationssystems
Dr.AdrianTangatJPLhasuniquepartnershipwithUCLAteamandQualcommfordevelopmentof
CMOSVLSIchipsforspaceapplications
“SPECTROCHIPII”has750MHzbandwidth,512spectralchannels,includesdigitizer,data
accumulator,andUSBoutputinterface
5x10cmsizeonboardwithsupportcircuitry;200mWDCpower
Thenextgenerationwillhave3GHzbandwidth,8Kchannels
Thelowpowerandmasswillallowsimultaneousoperationofmultiplereceivers
Spectrochip II
Full SoC Die Photo
v A Full 1.5 GS/s spectrum analyzer chip in
advanced 65nm CMOS was developed by
UCLA’s high speed electronics lab.
v Integrated 7b digitizers, offset and interleaving
calibration functions, clock management
system and vector accumulation.
v 256dsb/512ssb channel quadrature output with
integrated USB 2.0 controller
Full SoC Block Diagram
Module Assembly
IncreasedSensitivity(wrt Herschel)RequiresaLarger
Telescope
• Increasesampleofcomets:5/yearminimumtoget15-25in3to5
yearmissionwilldramaticallyimprovestatisticsandcoverageof
differenttypesThisrequires2-4xhighersensitivity;cometemission
&missionmodelingrequired
• Increasedsensitivitytostudywaterisotopologues inabsorption;
signalproportionaltocollectingarea
• Greatersensitivityessentialtomakestudyofwaterindisksbeyond
thenearestfewpossible
• Improvedangularresolutiontoimagevelocityfieldthroughoutcores
includingmoredistanthigh-masscores(Herschelhad40”FWHMat
557GHz)
WaterProbeMissionTelescope
Narrowlinewidthsrequirehighresolution(<0.25km/s;R>106)
Theonlyviableapproachisheterodynereceivers
Theemissivityofopticsat250μm islowenough(andreceivernoise
highenough)thatTELESCOPETEMPERATUREISUNIMPORTANT
Telescopeandmissiondesignrequirereasonablethermalstabilityto
maintainsurfaceandpointingaccuracy(𝝈 <15μm)
L2isagoodlocationfromtheseviewpoints.Passiveradiationwilllikely
bringtelescopeto~100K(needsfurtherstudy)
Willneedlargesunshield
ObservingmodesimilartoHerschel:targetsin40o wideconehaving
axisalongspacecraft-sundirectionbetweenobservable
WaterProbeTelescope
6-7mdia.DeployableCassegrainReflectorfitsinshroudof
Falcon9Heavy
Thisversionemploys36~1mhexagonalpanels
Originalengineeringstudyemployedan“optical”f/Dratio
withverylongsecondarysupportstruts
Relatively“JWST-like”
Limitingminimumwavelengthto250µmmeansthat
accuracyrequirementis100xlessdemanding
PossiblematerialsincludeSiC(asHerschel)butcouldalsobe
madeofcarbonfibercore+aluminumskins
ThankstoOttoPolancoforgraphics
DeployableQuasi-Monolithic
TelescopeStructure
10mx12msingle-layersunshadewithsolarpanelsonlowerside
WaterProbeMission
• Proposalsubmittedon15NovembertoNASA
• 15-monthstudyproposedincludingTeam-XstudyatJPL
• Opentocommunity;twoworkshopstodefineinstrumentand
mission
• Selectionbasedonscientificinterestandplausibilityof<$1Btotal
cost
• Selection– sometimeinSpring2017