From NAOS to the future From NAOS to the future SPHERE Extreme AO SPHERE Extreme AO systemsystemT. Fusco1, G. Rousset1,2 , J.-L. Beuzit3, D. Mouillet3,

A.-M. Lagrange3, P. Puget2 and many others …

1ONERA, Optics Department, Châtillon,2LESIA, Obs. de Paris, Meudon, 3LAOG, Obs. de Grenoble

Mail: thierry.fusco@onera.fr

On sky since Dec 2001

Consortium: ONERA-LAOG-LESIA Main characteristics

DM: 185 actuators 2 WFS: Visible and IR

14x14 and 7x7 sub-apertures Frequency: 15 to 480Hz > 80 configurations

Fine differential tracking: refraction, flexure, moving object

Non common path Aberration pre-compensation

Fully integrated and optimized system

NAOS : a multi-purpose AO system

VLT Nasmyth focus: NAOS + CONICA

NAOS

CONICA

NAOS on-sky performance ~ 60% Strehl ratio in K at seeing < 1 arcsec and MV<10 or MK<7

Strehl loss: telescope vibrations, calibration errors

Faint NGS: ~5% Strehl at MV~17.5 or MK~13.5

NAOS: example of results (I)

NGC 1068 active nucleus(D. Rouan et al., A&A, 2004)

2,2 µm 3,8 µm 4,8 µm

Hot dust cloud structures in the nucleus, the arms and to the North

NAOS: example of results (II) First extrasolar planet detection

To go further => dedicated instrument with eXtreme AO

K = 5 @ 0.778’ Teff~1200/+-200K 5-12 Myr, 5+/-2 Mjup(Chauvin et al.,

2004&2005)ESO/CNRS/UCLA

Requirements for Extra-solar planet detection

High contrast capability

Extreme AO (turbulence correction) Feed coronagraph with extremely well corrected

wavefront

Coronagraphy (removal of diffraction pattern) dynamics at short separation < 0.1”

Differential imaging (removal of residual defects) Calibration of internal system defects

Smart post processing algorithms Calibration differential aberrations

High sensitivity Optimal correction up to Vmag~10

Large number of targets

Direct detection : small separation (1-100 AU) small separation (1-100 AU) Large magnitude difference Large magnitude difference m >m > 1515

Lessons learned from NAOS

AO is NOT a separate instrument, it is a sub-system Global trade-off with focal plane modes (definition and design)

In an AO design the simpler is the better ! (as far as possible) do not try to do everything with a single AO system

Stability is a critical issue

AO has to correct for : Turbulence AND system defects (non common path aberrations, vibrations

…)

Error budget list is always larger than you thought !

ChallengingChallenging technologies :technologies : DM : 185 1370 actuators CCD : 500 1200 Hz = 5e- < 1e- RTC : > x10

1 order of magnitude better than NAOS

System aspect: System aspect: Control of 1370 actuators System calibration Filtered-SH and pupil stabilisation L3CCD Dedicated Tip-Tilt sensor at the level of the coronagraphic mask Differential aberration calibration and much more ...

NAOS SAXO

AO system (SAXO): the challenges (I)

AO system (SAXO): the challenges (II)

Vibrations Main limitation on 10-m class AO

systems (NAOS, Keck, Altair) Solution: Kalman Filter (predictive control laws)

Class. integrator

Kalman filter

Vibrations

Test of Kalman filter on ONERA AO bench

See C. Petit et al Optics Letter (submitted)

Non common path aberrations (From dichroic down to scientific detectors)

Reduce SR : typically more than 20 % of SR@1.6 m

Solution: Pre-compensation by AO loop Phase diversity measurements WFS reference modification

no pre-comp after pre-comp

SR = 70 % 96.5 % @ 633nm Exp. Validation on ONERA AO bench

See Sauvage et al., 5903, SPIE 2005

Nasmyth focus Environment: static bench, Nasmyth platform

0.9 – 2.3 µm; /2D @ 0.95 µm Differential imaging: 2 wavelengths, R~30, FoV = 13.5’’Long Slit spectro (grism), R~50/500

Common Path

High frequency AO correction (41x41 act.)High stability : image / pupil controlRefraction correctionVisible – NIR, FoV = 13.5’’

VisAO sensing F-SH WFS in visible, 40x40

1.5 KHz, RON < 1e-

Visible Channel (Zimpol) PolarimetryLyot coronagraph

NIR

Corono

IRDIS

Pupil apodisationFocal masks: Lyot, 4-QPupil stop IR-TT sensor for fine centering

IFS 0.95 – 1.7 µm λ/2D @ 1.05 µm 254x254 lensesSpectral sampling 0.04 m

Current SPHERE optical design

ForeopticsITT

DM

IR WFS

IRDIS

ZIMPOL

IFS J (phase A)

Vis WFS

Preliminary instruments optical implantationPreliminary instruments optical implantation

Current SPHERE implementation @ VLT

Expected performances

+ calibration• Reference star • WFS data

m = 15

• Detection up to 100 pc (depending on age and type)• Masses > Jupiter • Distance star-planet > 0.1”

> 1 AU at 10 pc

1

2

Assumed defects (conservative): Seeing variation (obj/ref) = 10 %

Reference decentering = 0.5 mas

Reference Pupil shift = 0.6%

Diff WFE = 10 nm

Additional non turbulent jitter = 3 mas

Conclusion and perspectives NAOS

Multi-purpose system On sky since 2001 Large number of astrophysical results (more than 75 articles in ref. journals)

SPHERE / SAXO Optimized instrument (and AO system) for exoplanet detection Extremely challenging system (very tight error budget) Realization phase has begun (kick off last week) First light expected in 2010 LAOG-LAM-LESIA-ONERA / ESO / MPIA Heidelberg / Obs de Geneve-

Zurich / Obs de Padoue / Univ. of Amsterdam-ASTRON

Next step: ELTs Technical challenges: act. Numbers, comp. time, optics with sub-nm accuracy Performance challenge: WFE error budget