VISMCAOattheVLTAOF!

S.Esposito,G.Agapito,M.Bonaglia,L.Busoni,INAF-ArcetriT.Fusco,B.Neichel,LAM

VLTAO-Communityday20-21Sept.,2016

Sep2015:AOFfactsandconsidera7onsØ AdeformablesecondarymirrorDSMwith1170actuators,conjugatedto~ground

Ø Fourlaserguidestars20weach,drivinga40x40SHSforGLAO(4WFSsintotal).

GLAOforNIRandVIS,narrowfieldmodeforVIS

SCAOwithNGSandLGS(ERIS)

Addingpost-focalDMsischangingthegame=>increasecorrectedFoVbeyondlimita[onofnaturalangularanisoplana[sm.

~20cmactuatorspacingprojectedonM1

Considerusingthe21cmspacing(and420Wlaser)topushcorrec[ontoshorterwavelengths.

AVisibleLGSM

CAOsystemwith20

arcsec

FoV(2DMs)

Correc7oninthevisible……650nmimagesfromForerunneratLBT

…visibleisdoable….

-welltuned500modesreconstructors-NCPAcompensatedat6and3lambda/D-indomepsfswithandwithout0.8seeingturbulenceshowingStrehlof50%.

similarimagesfromSPHERE…

A)  Largevisibledetectorsarecheap(comparetoNIR),anddetectorquality

ismuchbeder(darkcurrent,cosme[c,warmandsimple)B)  B)Skybackgroundissmall(1000to10000[mesdarkerthanK),

differencewithspaceissmalltoo.C)“low-noise”(<1e-RON)large(4kx4k)andfast(10frame/seconds)detectorsalreadyexist!(e.g.Gachetal.)

C1:PostprocessingTip-Tiltcorrec[on(100%skycoverage,imagesarere-centeredpost-facto)C2:Higherorderpost-processing(e.g.mul[-framedeconvolu[on)inordertorecoversomeofthepar[alcorrec[onoftheAO

=>C1,2mayrelaxsignificantlytheconstraintsontheAOsystem!

Advantagesofvisibleobserva7onsw.r.t.NIR

VISMCAO4VLT:talksummaryAfirstassessmentof#ofLGSsand#ofDMsconsideringAOFavailabiltyi.e.4LGSsandDSM(1170acts)

E2Esimula[onexploringrestrictedparameterspaceforLGSsandDMs(assumeVLTenvironmentalparameters)

compareVLTandHSTPSFsat650nm:SNRinRbandfilter

ConclusionsaboutVISMCAOperformance(andFoV)

A5(4)LGSs&2post-focalDMsoptomechanicalsketch.

Basiclimi7ngfactorsforVISMCAOsystem

totalwferror:wewanttoachieve~30%SRat650nm(e.g30%ofenergyina2lambda/Dpatch),requires~1rad^2overallAOerror.At650nm1radeq.to~100nm

(1)generalizedanisoplana[sm(&fipng)error(#DMs,#Acts)(2)tomographicerror(#ofLGS,thetaofLGS)

Tomograficreconstruc[onandDMscorrec[onefficiency

plotdoesnotincludefipngerror(dact/ro)^5/3

CHAPITRE 8. QUELLE OA POUR EAGLE?

Fig. 8.3 – En haut : influence du nombre de DMs sur l’EE moyenne en fonction de la tailledu champ scientifique. En bas : illustration du residu de correction (en niveau de gris) enfonction de l’altitude et de la frequence spatiale pour deux ou trois DMs.

Le principal avantage de cette methode est que l’on peut alors envisager de travailleren boucle fermee, ou plutot en “pseudo boucle fermee”. En e↵et, dans le cas de la SMCAO,chaque ASO associe aux etoiles lasers sera place derriere le DM associe a son sous-champen plus du M4. Compare a une configuration boucle ouverte, cela permet de reduire ladynamique necessaire sur les ASOs1. De plus, chaque DM post-focal est vu par un ASOce qui permet d’en controler les formes et de reduire l’impact des non-linearites.

1Il faut tout de meme noter que les ASOs voient une correction “onde plane” des DMs, alors que l’onde

incidente est spherique. Autrement dit, chaque ASO subit l’e↵et de cone ce qui necessite une dynamique

de mesure importante.

Memoire de these Benoıt NEICHEL 244

tel-0

0366

529,

ver

sion

1 -

8 M

ar 2

009

CHAPITRE 8. QUELLE OA POUR EAGLE?

Fig. 8.3 – En haut : influence du nombre de DMs sur l’EE moyenne en fonction de la tailledu champ scientifique. En bas : illustration du residu de correction (en niveau de gris) enfonction de l’altitude et de la frequence spatiale pour deux ou trois DMs.

Le principal avantage de cette methode est que l’on peut alors envisager de travailleren boucle fermee, ou plutot en “pseudo boucle fermee”. En e↵et, dans le cas de la SMCAO,chaque ASO associe aux etoiles lasers sera place derriere le DM associe a son sous-champen plus du M4. Compare a une configuration boucle ouverte, cela permet de reduire ladynamique necessaire sur les ASOs1. De plus, chaque DM post-focal est vu par un ASOce qui permet d’en controler les formes et de reduire l’impact des non-linearites.

1Il faut tout de meme noter que les ASOs voient une correction “onde plane” des DMs, alors que l’onde

incidente est spherique. Autrement dit, chaque ASO subit l’e↵et de cone ce qui necessite une dynamique

de mesure importante.

Memoire de these Benoıt NEICHEL 244

tel-0

0366

529,

ver

sion

1 -

8 M

ar 2

009

theta>17”,2DMsalwayslimitedby#ofDMs

theta<45”,3DMsalwayslimitedby#ofLGS

plotshowingresidualrmsforWFreconstruc[onandDMsplacementsop[mizedforscienceFoV~eq.toLGSasterism

tomogenaniso

datafromT.Fusco,LAM

70nm

Basicerrorbudget

1)tomo+gen_anisoplana[s=~90nm2)DMfipngerror~50nm(DSM)3)LGSphotonnoise~504)TTresidualNGS~30nm(fromE2Emodaldecomposi[on)

VLTAOFenvironmentalparametersassumed.-ExpectedfluxesforESOAOF(~100phot/ms/sub,40x40sub)-seeing=0.73arcsec-L0=25m

3DMs(2postfocal&5LGS)sigma_tot~125nn….movetoE2Esimula[ons

E2Esimula[onsmainparameters•  Atmosphere:

–  Seeing(@zenith)0.66”–  L025m–  Cn2ERISprofile(10layers)–  zenithangle30°–  inputwfstd.dev.1042nm

•  NGS:–  WFS:2x2SH–  GSon-axiswithR=12,19

•  LGS:–  WFS:4,5&940x40SH–  asterism:

•  4LGS@FoV(150fot/sub/frame)•  5LGS:4@Fov+1on-axis(150fot/sub/frame)

•  9LGS:4@FoV+4@FoV/2+1on-axis(75fot/sub/frame)

•  DM1(ASM1172acts):–  Height0m–  945KLmodes

•  DM2(ALPAO241acts)–  Height5000m–  252KLmodes

•  DM3(ALPAO241acts)–  Height10500m–  252KLmodes

4+1LGS~3+1LGS,maysavecentralLGS,(TBC)

Asterisms:

E2Eresults@650nmAnima[on!(1)brightLGS(x10);(2)brightNGS(mag12);(3)centeredNGS

Resultscomparison

courtesy:M.LeLouarnCourtesy:T.Fusco

MLeLouarn&T.Fuscosimula[onresultsinagreementwithArcetriones.

(Briefly)Effectsof:(1)offaxisNGS,(2)fluxofNGS,(3)fluxofLGS,(4)3+1~4+1(whenLGSisconcerned)

3+1~4+1(whenLGSisconcerned...)

FWHM

EE50%

SR

BrightLGS(x10)BrightNGS(R=12)On-axisNGS

performanceof3+1LGSsisslightlyworsethan4+1but3+1isdoablewithpresent4LGSofAOF

BrightNGSoffaxis

EE50%

FWHM

SR

FaintNGSonaxis:results@650nmEE

SR

Rmag19thgivesslightlyreducedSRsovertheFoV,Hbandsourceshouldimproveresults

Differencesarelimitedtofirst10-20mas

EEprofiles

FWHM

SR

System SC: tip tilt reference star

16

FoV for

30% R<15 R<16 R<17 R<18 R<19

sky cov.@GP [as] [as] [as] [as] [as]

GSCNGP 86 67 53 41 29NOMADNGP 81 64 51 40 31

GSCSGP 84 66 51 40 30NOMADSGP 80 63 50 41 33

Average 83 65 52 41 31

3x104randomdirec[onsin5°radiuscirclearoundGalac[cPoles.GSCandNOMADcatalogues

usingpostprocessingwithfastreadoutVISCCDstoreduceneedsforNGSstar

realLGSfluxes:results@650nmFWHM

SR

EE50%

FWHMSR

BrightLGS(x10)VSTruefluxLGSBrightNGS(R=12)On-axisNGS Casewiththelargestvaria[onfound

Opto-mechanics2postfocalDMs4+1(3+1),8+1LGS1ormoreNGS(VISorNIR)

MCAOrelayarrangement

DM10km

DM5km

K-mirror(removeseleva[on:M2&LGSsarefixed)

OAP2

OAP1

LGSdichroic(foldsNGSlightbelowMCAObench) NGSfocus

(mustbemechanicallyderotatedtofollowsky)

~500mm

VLTlight

NGSandLGSfootprintsonDMs

DM@5kmDiam.max=44mm

9xLGSfootprint:Max22.5’’off-axis

DM@10kmDiammax=44mm

NGSfootprint:Max22.5’’off-axis

IRNGSWFSfocus

9xLGSWFSs

DM5km

MCAObench&LGS9xWFSsarrangement

Blue=NGS+LGSlightpathYellow=LGSlightpath

DM10km

InstrumentVISfocus

LGStrombone

NGS/LGSdichroic

NGSpartadachedtomechanicalderotatortotracksky

9xLGSpickoff~1000mm

LGSTrombone

LGS2xbeamexpander

9xLGSWFSbelowMCAOrelay

~1000m

m

8xpickoffmirrors(inred)for11.25’’and22.5’’off-axisLGSs(10mmdiameter)On-axisLGSistransmided

from45x45arscecto90x90

possibili[esforadoublesizeFoVlike90x90withsameperformances:1)op[ona:MCAOsystemwitha4-5postfocalDMsand~10LGS2)op[onb:a2x245x45arcseca)2postfocalDMsb)5WFS/LGS(4+1)[led,atotalof9LGS3)op[onc:….

3DMs:DSM+2postfocalDMs,5LGS(4+1)

AlreadydiscussedinthepastbyR.Ragazzoni&B.NeichelfigurefromB.Neichel,LAM

HSTandVLTVIScomparison

JWSTinVIS

“JWSTwillbediffrac0onlimitedat2μm,definedashavingaStrehlra0o>0.80.JWSTwillachievethisimagequalityusingusingperiodicwave-frontsensingandcontroloftheprimarymirror.Theobservatoryandpoin0ng-controlsystemaredesignedtolimitimagemo0ontolessthan7milliarcsecondsduringobserva0ons.”

80%SRat2um=>142nmrms,thisgivesa15%SR,assumingno[p[ltresidualerror.

hdps://jwst.stsci.edu/instrumenta[on/telescope-and-poin[ng/image-quality-and-psfs

HST&VLTVISMCAOwearereferringtoACS/WFCinthefollowingdiscussion

VLTMCAOVISvsHST/WFCObjectdetectedfluxforR=25:•  VLT=20.0ph/s•  HST=2.0ph/sBackgroundflux:•  VLT=846ph/asec2/s•  HST=35ph/asec2/sPlateScale:•  VLT=10mas•  HST/ACS-WFC=50masRON:•  VLT=2e-/pixel•  HST/ACS-WFC=8e-/pixel

Throughputinsimula[onsHSTACS-WFCF625W-77~0.4,[548-707]VLT(VIMOSRfilter)~0.3,[558-730]

SNR = γ source γ source +γbckgρ2 +σ ron

2 ∗npix

Results@650nm

RAWContrast EncircledEnergy%

(1)realLGSflux,(2)NGS12mag(3)NGSonaxis

curvesofthesamecolorrepresentprofilesindifferentposi[onoftheFoValwaysgivenasdiameter

SourceR=25@650nm,brightNGS

Profilesinphotons

EEinphotons

SNR←y-Linear→y-Log

RealLGSfluxBrightNGS(R=12)On-axisNGS

SourceR=30@650nm,brightNGS

Profilesinphotons

EEinphotons

SNR←y-Linear→y-Log

RealLGSfluxBrightNGS(R=12)On-axisNGS

SourceR=30@650nm,faintNGS

Profilesinphotons

EEinphotons

SNR←y-Linear→y-Log

RealLGSfluxBrightandFaintNGSOn-axisNGS

Resumingcomparison:dt=1000ssourceRmag

SNRHSTACS/WFC SNRVLTVISMCAO SNRra7o

Exp.7me

10mas 50mas 10mas 50mas

25 13 30 49 55 3.8-1.8 14.4-3.4

30 0.28 0.56 1.6 0.77 5.7-1.9 32.5-1.7

Ø  30magRstaratSNR=5Ø  VLT~10^4s(2.7h)over20masdisk² HST~8e4s(22h)over100masdisk² HST~3.2e5s(88h)over20masdisk

correctedFoVis30x30or45x45withminorlossesinperformance(2postfocalDMs,5LGS)

ConclusionsIØ  errorbudgetsandE2Esimula[onsshowsthat

AOFHWASM+4LGSplus2small(50mm)postfocalDMsprovidesagoodMCAOsystemforVIS(650nm),<SR>30%for30”diameter.

Ø  2postfocalDMs,4+1LGS(30”or45”)and5WFSs40x40subapertures.Afirstcompact1mx1mx1marrangementforoptomechisoutlined.

Ø  ona30magsource(in1000s)VLTachievesbederSNRthanHST.Upto67meson10masradandupto1.9on50masrad.VLTdetects30magatSNR=5in2.7hagainstHST22h.

2yearspost-docposi[onavailableatLAMtoworkonWideFieldAOVLT3

ConclusionsII

TheVISMCAOatVLT(doesbenefitalotfromAOFexis[ngHW):(1) itprovidesgoodperformancecomparedtoHST,

detectsmag30in~3h(HST~20h)at5xtheHSTspa[alresolu[on(10mas).

(2) itisdesignedusingcommercialDMsandparts,seemsoflimitedcomplexityandcost.