Technical Considerations for Telescope Architectures and ......Nov 09, 2016 · LUVOIR OTE RC Scale: 0.01 GJW 08-Sep-16 2500.00 MM Primary Mirror (PM) Secondary Mirror (SM) On-axis

Technical Considerations for Telescope Architectures

and Aperture Size

Ma#hewR.Bolcar,LeeFeinberg,Garre#WestGSFC

PresentedtotheLUVOIRSTDT

11/9/16

Objec+ves•  Reviewafewillustra(vetelescopedesigns

•  Three-mirroranas+gmat(TMA)vs.Ritchey-Chre+en(RC)•  Discussstrengths&weaknessofeach

•  On-axisvs.off-axisdesigns•  Relatedesignconsidera+onstoLUVOIRpriori+es

•  Instrumentaccommoda+ons•  Packagingforlaunchvehicle•  Testfacilityaccommoda+ons•  Aperturescalingrela+onships

TechnicalConsidera+onsforTelescopeArchitectures&LaunchVehicles 2

BasicIdea


15:42:41

LUVOIR 9.2m TMA Scale: 0.01 GJW 07-Sep-16

1923.08 MM

Three-mirrorAnas+gmat-SingleFocalPlane(TMA-SF)


PrimaryMirror(PM)

SecondaryMirror(SM)

TerKaryMirror(TM)

Off-axisTMAFocalPlane

InternalPupil&FineSteeringMirror

(FSM)

TMA-SFAdvantages•  Threemirrorssimultaneouslycorrectspherical,coma,andas+gma+smaberra+ons

•  Enablesdiffrac+on-limitedperformanceoververywidefields-of-view(>8x8arcmin)

•  Accesstoaninternalpupilallowsforaddi+onalcorrec+on:•  Poin+ngcontrolwithafine-steeringmirror(FSM)•  Ac+vecontrolwithadeformablemirror(DM)

•  Heritage:JWST


TMA-SFDisadvantages•  Atleastfourreflec+onsbeforeenteringinstruments

•  Morearelikelyinordertofoldbeamforpackaging•  Lowerthroughputforsensi+veinstruments(UV&coronagraph)

•  Complexa_-op+calsystem(AOS)•  Complicatessystemalignment•  Couldpresentdifficultyforinstrumentpackagingbehindtelescope

•  JWSTexperienceindicatesstray-lightcanbedifficulttobaffle


Three-mirrorAnas+gmat-DualFocalPlane(TMA-DF)


11:16:46


1923.08 MM

11:11:13


1923.08 MM

PrimaryMirror(PM)

SecondaryMirror(SM)

TerKaryMirror(TM)

Off-axisTMAFocalPlane

InternalPupil&FineSteeringMirror

(FSM)

On-axisCassegrain

Focus

TMA-DFAdvantages•  NarrowFOVon-axisCassegrainfocus

•  Only2reflec+onsforhigh-throughput(UV&coronagraph)instruments

• WideFOVoff-axisTMAfocus•  Well-correctedwide-FOVinstruments•  Silvercoa+ngonTM,FSM,etc.forop+mizedVis/NIRperformance

•  AccesstoaninternalpupilinTMAchainallowsforaddi+onalaberra+oncorrec+on(butonlyinTMAfocalplane):

•  Poin+ngcontrolwithafine-steeringmirror(FSM)•  Fixedpupilplatecorrector•  Ac+vecontrolwithadeformablemirror(DM)

•  Heritage:WFIRST


TMA-DFDisadvantages•  Mustbalanceaberra+onsbetweenbothfocalplanes

•  RequiresapupilcorrectorplatetorecoverimagequalityatTMAfocus

•  Moredifficultpackagingconfigura+onsincebothfocalplanesneedtobeaccessible

•  Mayrequiremorefoldmirrors,reducingthroughputintheTMAfocus

•  TheCassegrainfocusisverynarrowfield-of-view•  Arcsecondsinsteadofarcminutes


Ritchey-Chre+en(RC)


10:29:37

LUVOIR OTE RC Scale: 0.01 GJW 08-Sep-16

2500.00 MM

PrimaryMirror(PM)

SecondaryMirror(SM)

On-axisCassegrain

Focus

RCAdvantages•  Single,high-throughputfocalplane

•  Possibleforeveryinstrumenttoonlyseetwobounces(thoughsomefoldmirrorswilllikelybenecessary)

•  Simplifiedop+caltrainmeanslesscomplicatedalignmentandtes+ng

•  Heritage:HST


RCDisadvantages•  Narroweroverallfield-of-viewthanTMAdesigns

•  ~3x3arcmindiffrac+on-limited•  Instrumentsoutsideofthisfieldwillneedinternalcorrec+veop+cs•  Acurvedfocalplanecanhelpimprovetheimagequality,butmayrequiresomecrea+vityininstrumentpackaginganddesign

•  Noaccesstointernalpupilforafine-steeringmirror•  Putsallpoin+ngrequirementsonthespacecra_/disturbanceisola+onsystem

•  Orneedtoincludeindividualfine-steeringmirrorsinsideinstrumentsthatneedit


Field-of-ViewMap:9.2mTMA


8arcm

in

8arcmin

Diffrac+onLimited35nm

Field-of-ViewMap:12mRC


3arcm

in

3arcmin

Diffrac+onLimited35nm

On-axisvs.Off-axis•  Allofthesedesignswerepresentedasnominallyon-axis

•  Anyofthemcouldbemadetobeunobscuredoff-axis

•  Off-axisadvantages:•  No-obscura+onimprovesoverallthroughputandpossiblycoronagraphease-of-design/performance

•  Off-axisdisadvantages:•  Higherangles-of-incidenceatPM&SMàLargerpolariza+oneffects?•  Generallyincreasesaberra+onàSmallerwell-correctedFOV•  PM-to-SMdistanceincreasesàImpactsstability&packaging•  Unclearhowanoff-axissegmenteddesigncouldbepackagedtofitinsideofafairing


12:11:56

LUVOIR OTE RC Scale: 0.01 GJW 17-Oct-16

2500.00 MM

Off-AxisRitchey-Chre+en(RC)


PrimaryMirror(PM)

SecondaryMirror(SM)

On-axisCassegrain

Focus

InstrumentAccommoda+ons•  EachoftheLUVOIRinstrumentsmayhaveapreferenceforoneormoreofthesedesigns

•  Thefollowingslidesaddresseachinstrumentseparatelyanddiscussthetradesassociatedwitheachofthetelescopedesigns

•  Oncealloftheinstrumentperformancespecifica+onsareinhand,theengineeringteamwilldesignthetelescopetoop+mizeperformanceoveralloftheinstruments


Vis/NIRCoronagraph•  OnlyrequiresasmallFOV(~arcsecs)

•  Couldgoinanyfocalplaneofanydesign

•  CassegrainfocusoftheTMA-DF,andRCdesignareamrac+vefor:

•  Highthroughputduetoreducednumberofreflec+ons•  Bemerwavefrontstabilitywithfewerop+csinthepath

•  TMAfocusisamrac+vefor:•  Accesstoafine-steeringmirrorforbemerpoin+ngcontrol


LUMOS(UVMul+-objectSpectrograph)•  TMA-SFdesignisleastdesirable

•  Lotsofreflec+onsreducethroughput,BUT•  AllowsforwideFOV,withstablepoin+ngbehindaFSM

•  TMA-DFCassegrainfocus•  Improvesthroughputwithonlytworeflec+ons,BUT•  ExtremelylimitedFOV,poin+ngmustbeprovidedbyspacecra_

•  Ritchey-Chre+enisbestoverall•  Highthroughputwithonlytwobounces•  Achievable~3x3arcminFOV

•  Needtounderstandpoin+ngstabilityrequirementstodetermineifthereisaneedforaFSM


HDI–Vis/NIRWide-fieldImager•  ObviouslywantstobeateitheroftheTMAfocalplanesforwidefield-of-view

• Wouldneedinternalcorrec+veop+cstoworkwiththelimitedfield-of-viewoftheRitchey-Chre+en

•  Needsaddi+onalstudytodeterminewhat’sachievable

•  Needtounderstandpoin+ngrequirementsofastrometrymodetodetermineifanFSMisnecessary


Vis/NIRMul+-resolu+onSpectrograph•  Narrowfield-of-view?

•  Couldgoinanyfocalplaneofanydesign

•  Needtounderstandrequirementsforradialvelocitymeasurementstounderstandrequirementsontelescope


ExampleTMA-DFFocalPlaneLayout


10arcsec

10arcsec

8arcm

in

8arcmin

CassegrainFocus TMAFocus

3x3’LUMOS

2x2”Coro

4x6’HDI

Diffrac+on-LimitedPerformance:

2x2”HRS

11:16:46


1923.08 MM

11:11:13

LUVOIR 9.2m TMA Scale: 0.01 GJW 08-Sep-16 1923.08 MM

ExampleRCFocalPlaneLayout(1)


9arcmin

9arcm

in

3x3’LUMOS

3x6’HDI


10:29:37


2500.00 MM



9arcmin

9arcm

in

3x3’LUMOS

3x6’HDI


2x2”Coronagraphand2x2”HRSfields



9arcmin

9arcm

in

2x2’LUMOS


10:29:37


2500.00 MM



9arcmin

9arcm

in

2x2’LUMOS


2x2”Coronagraphand2x2”HRSfields

SummaryStoplightChart


Capability: TMA-SF TMA-DF RC

PresenceofHigh-ThroughputChannel

WideField-of-ViewCapability

CassegrainFocusField-of-View

AlignmentComplexity

InstrumentPackagingComplexity

AvailabilityofFine-SteeringMirror

Angle-of-IncidenceImpactonPolariza+on

SummaryStoplightChart


Capability: TMA-SF TMA-DF RC

PresenceofHigh-ThroughputChannel

WideField-of-ViewCapability

CassegrainFocusField-of-View

AlignmentComplexity

InstrumentPackagingComplexity

AvailabilityofFine-SteeringMirror

Angle-of-IncidenceImpactonPolariza+on

Op+cal/NIRCoronagraph

LUMOS

HDI

Op+cal/NIRSpectrograph

LUVOIRLaunchVehicleAccommoda+ons•  AssumeLUVOIRwillini+allyaccommodatefourormoreinstruments

•  ConceptsthatuseanSLSwith8.4-mor10-mdiameterfairingsareconsistentwiththisassump+on

•  SLSconceptswillbeconstrainedbycostbeforemasstoorbitorfairingvolumeconstrainsthenumberofinstruments

•  Otherlaunchvehicles(SpaceX,BlueOrigin)worthkeepinganeyeon

•  Conceptsthatusealaunchvehiclewitha5mdia.fairing(likeDeltaIVHeavy)aremorechallenging

•  Instrumentstudiescanprobeforrisksandmethodsofmi+ga+on


LUVOIRLaunchVehicleAccommoda+on


SLSBlock2B50kkgtoL2orbit10mfairing

SLSBlock1B38kkgtoL2orbit8.4mfairing

DeltaIVHeavy10kkgtoL2orbit5mfairing

Feasible NotFeasible NeedsValida+on

TelescopeApertureDiameter(m):

LaunchVehicle:

MassMarginVolumeMargin

MV

MV

MV

6.5 9.2 12 16 20

LUVOIRLaunchVehicleAccommoda+on


SLSBlock2B50kkgtoL2orbit10mfairing

SLSBlock1B38kkgtoL2orbit8.4mfairing

DeltaIVHeavy10kkgtoL2orbit5mfairing



LaunchVehicle:

MassMarginVolumeMargin

MV

MV

MV

6.5 9.2 12 16 20

Toachievenecessarys+ffnessrequiresathickbackplanethatconsumesvolume.

LUVOIRTestFacility(JSC)Accommoda+on•  LN2islikelyrequiredforthermalbalancetests

•  Heliumshroudnotneeded

•  Assumingaroomtemperaturetelescope:•  Sometestsperformedinvacuumwithautocollima+ngflats

•  Sometests,likecenterofcurvatureconductedinambientenvironmentinacleanroom

•  BothtestsleverageJWSTexperience

•  SecondaryMirrorwilllikelyneedtobedeployedorinstalledinsidethechamber

•  Need~2-meterclearancearoundedgeforaccess,cables,etc.

•  Demonstratethermalstabilitywithsubscaletes+ng(e.g.singlewingofmirrors)

•  Dynamicsdemonstratedincleanroomandthroughmodelvalida+ons


LUVOIRTestFacility(JSC)Accommoda+on


VacuumVesselDiameter(19m)Height(36m)

LN2ShroudDiameter(16m)Height(28m)

HeliumShroudDiameter(13m)Height(20m)



FacilitySizes:

DiameterMarginHeightMargin

DH

DH

DH

6.5 9.2 12 16 20

Addi+onalAperture-drivenValues*:


D(meters)

Area(m2)

NumberofSegments

HeaterPower(W)

MirrorMass(kg)

BackplaneMass(kg)

BackplaneThickness

(m)

TotalPMMass(kg)

6.5 33.2 18 627 829 1327 0.33 2156

9.2 66.4 36 1257 1661 2658 0.66 4319

12 113.0 61 2139 2826 4522 1.12 7348

16 201.0 109 5024 5024 8038 1.98 13062

*Backoftheenvelopecalcula+ons.Assumes293Kopera+ngtemperatureandslightly-bemer-than-JWSTarealdensity.

RemainingTelescopeArchitectureDecisions:


Aperturesize(s) Yourvotetoday!

Observatorytemperature Redcutoffvs.acceptablecostandrisk

Telescopeop+caldesign InstrumentFOVsInstrumentpoin+ngrequirementsInstrumentimagequalityrequirements

On-vs.Off-axis Outcomeofpolariza+onstudiesInves+ga+ngdeployment/packagingop+onsImpactonexoplanetyield

Documents

Technical Considerations for Telescope Architectures and ......Nov 09, 2016 · LUVOIR OTE RC Scale: 0.01 GJW 08-Sep-16 2500.00 MM Primary Mirror (PM) Secondary Mirror (SM) On-axis