s. oberti the eso adaptive optics department · clean room, beam diagnostic systems, lidar,...

RingbergRingberg, 1st November 2007, 1st November 2007

The VLT Adaptive Optics FacilityThe VLT Adaptive Optics FacilityS. S. ObertiOberti

&&the ESO Adaptive Optics Departmentthe ESO Adaptive Optics Department

Talk Talk -- RingbergRingberg -- Astronomy with LGS AO Astronomy with LGS AO -- S. S. ObertiOberti

AO Facility DescriptionAO Facility Description

ASSIST

4 LGSsLaser Room

GALACSI MUSE

GRAAL Hawk-I

Deformable M2

Concept of Adaptive Telescope, EConcept of Adaptive Telescope, E--ELT prototypeELT prototype4 (5?) Sodium Laser Guide Stars4 (5?) Sodium Laser Guide StarsGRAAL/HawkGRAAL/Hawk--I I

7.57.5’’ FOV near IR / GLAO correctionFOV near IR / GLAO correction1.3 gain on the EE in 0.11.3 gain on the EE in 0.1”” pixelpixel

GALACSI/MUSE IFS with:GALACSI/MUSE IFS with:GLAO wide field mode 1GLAO wide field mode 1’’Gain factor 2 on EE in 0.2Gain factor 2 on EE in 0.2”” pixel at 750 nmpixel at 750 nmLTAO narrow field mode 7LTAO narrow field mode 7”” -- Sr(650nm) ~ 10%Sr(650nm) ~ 10%

CassegrainCassegrain focus available (MCAO, on axis AO?)focus available (MCAO, on axis AO?)Enabling technologies:Enabling technologies:

1.1 m convex aspherical Deformable M2, 1170 act. 1.1 m convex aspherical Deformable M2, 1170 act. 2 mm Zerodur thin shell2 mm Zerodur thin shellRaman Raman fibrefibre laserlaser~0 noise, 240x240 pix., 1kHz WFS~0 noise, 240x240 pix., 1kHz WFS--CCDCCDRTC: computing power 200 x NAOSRTC: computing power 200 x NAOS

Test bed for calibration, operation and control of a Test bed for calibration, operation and control of a LGS adaptive telescopeLGS adaptive telescopeLaboratory testing facility (ASSIST)Laboratory testing facility (ASSIST)OnOn--sky: 2011sky: 2011--20122012


The DSM overviewThe DSM overview

M2M2--Unit functions: focus, centering, tilt/chop Unit functions: focus, centering, tilt/chop (Hexapod, focal switcher, thin shell)(Hexapod, focal switcher, thin shell)1.47 kW power consumption1.47 kW power consumption1170 voice coil actuators & capacitive sensors1170 voice coil actuators & capacitive sensorsThin shell mirror with magnets glued on; Thin shell mirror with magnets glued on; f=1120mm, 2mm thin, ~9 kgf=1120mm, 2mm thin, ~9 kg62 nm RMS fitting error; 0.5msec rise time; 80 62 nm RMS fitting error; 0.5msec rise time; 80 kHz internal control loopkHz internal control loopIntegrated design, maintenance provisions (LT Integrated design, maintenance provisions (LT compatible)compatible)


4 Launch Tel. mounted on Center piece4 Launch Tel. mounted on Center pieceBaseline is UT4; Other UT makes sense?Baseline is UT4; Other UT makes sense?4x 1178 nm 4x 1178 nm fibrefibre Raman Lasers doubledRaman Lasers doubledLaunch Telescopes refractive f=30cm; Launch Telescopes refractive f=30cm; Support by Support by carboncarbon--fibrefibre reinforced shellreinforced shell (high (high rigidity; rigidity; eigenfreqeigenfreq. > 60 Hz, 326 kg). > 60 Hz, 326 kg)Field steering (up to 330Field steering (up to 330”” radius) via the radius) via the piezopiezo--driven driven ØØ 0.7 cm 0.7 cm 4545°°--mirrormirror before lensbefore lensClean Room, Beam Diagnostic Systems, Clean Room, Beam Diagnostic Systems, LIDAR, Aircraft avoidance system & Safety LIDAR, Aircraft avoidance system & Safety SystemsSystemsRayleigh Lasers Rayleigh Lasers ““backupbackup”” droppeddropped

AO Facility: 4LGSFAO Facility: 4LGSF

589 nm>10 W, < 2 GHzSingle-pass

frequency-doubling in PPNLC

1178-nm fibre Raman laser> 20 W, < 1 GHz

~ 25 m

Actual LGSF commissioning is an invaluable experience

for the 4LGSF


PowerPC744x

VirtexIIVP70

3.1Gbps

VirtexIIVP70

MEM PCI-X

PowerPC744x

MEM PCI-X

EthernetPMC

PCI-X

VirtexIIVP30

TS201

TS201

TS201

TS201

MEM

VirtexIIVP30

TS201

TS201

TS201

TS201

MEM

64

IF

VirtexIIVP30

TS201

TS201

TS201

TS201

MEM

VirtexIIVP30

TS201

TS201

TS201

TS201

MEM

64

IF

LCU

VME64

Zero Latency Switch

CODE

HKL

HSDL

HV

DM

NGC

Gigabit Ethernet Switch

INS Workstation

DTTMPTTMITTM

Auxiliary Parallel Workstation

VLT LAN

NGC

SPARTA RTCSPARTA RTCSPARTA Conceptual Design v3

Low latencyHard real-time

Simple functionsLow flexibility

High latencySoft real-time

Complex functionsHigh flexibility

Non real-timeHigh level functions

High flexibility


PowerPC744x

VirtexIIVP70

3.1Gbps

VirtexIIVP70

MEM PCI-X

PowerPC744x

MEM PCI-X

EthernetPMC

PCI-X

VirtexIIVP30

TS201

TS201

TS201

TS201

MEM

VirtexIIVP30

TS201

TS201

TS201

TS201

MEM

64

IF

VirtexIIVP30

TS201

TS201

TS201

TS201

MEM

VirtexIIVP30

TS201

TS201

TS201

TS201

MEM

64

IF

LCU

VME64

Zero Latency Switch

CODE

HKL

HSDL

HV

DM

NGC


INS Workstation

DTTMPTTMITTM


VLT LAN

NGC

SPARTA RTCSPARTA RTC

SPARTA Conceptual Design v3

AcquisitionFrom pixels to

gradients- FPGA -

ReconstructionFrom gradients to

mirror deltas- DSP -

ControlController, saturation

& anti wind-up- DSP -

ControlKalman & auxiliary

loops- CPU -


PowerPC744x

VirtexIIVP70

3.1Gbps

VirtexIIVP70

MEM PCI-X

PowerPC744x

MEM PCI-X

EthernetPMC

PCI-X

VirtexIIVP30

TS201

TS201

TS201

TS201

MEM

VirtexIIVP30

TS201

TS201

TS201

TS201

MEM

64

IF

VirtexIIVP30

TS201

TS201

TS201

TS201

MEM

VirtexIIVP30

TS201

TS201

TS201

TS201

MEM

64

IF

LCU

VME64

Zero Latency Switch

CODE

HKL

HSDL

HV

DM

NGC


INS Workstation

DTTMPTTMITTM


VLT LAN

NGC

SPARTA RTCSPARTA RTC

SPARTA Conceptual Design v3

Real-timeData transfer

GbE

Data bufferingDiagnostic, Calibration

online optimizationStatistical analysis

CCS InterfaceReal-Time Display

Control Panels


ASSIST (test bench) Optical DesignASSIST (test bench) Optical Design2.52.5’’ unvignettedunvignetted FoVFoV, f/15 output, f/15 outputDiffraction limited on axis, stringent pupil imagingDiffraction limited on axis, stringent pupil imagingrequirement across the whole requirement across the whole FoVFoV (<1% distortion)(<1% distortion)Simultaneous LGS & NGS sources whose size/positioSimultaneous LGS & NGS sources whose size/positioillumination can be changedillumination can be changed3D turbulence, 3 phase screens for seeing and 3D turbulence, 3 phase screens for seeing and anisoaniso..M1 aspheric concave of 1.6 m diameter at f/1M1 aspheric concave of 1.6 m diameter at f/1M2 aspheric convex of 140 mm at f/1.3M2 aspheric convex of 140 mm at f/1.3


ASSIST Mechanical DesignASSIST Mechanical Design


GLAO: Practical implementationsGLAO: Practical implementationsGRAAL: GRAAL: GRGRoundound layer layer AAO O AAssisted with ssisted with LLaseraser

Goal: Goal: reduce by 15 % in Y and 30% in Ks band the diameter reduce by 15 % in Y and 30% in Ks band the diameter collecting 50% of the encircled energy over 7.5collecting 50% of the encircled energy over 7.5’’ FOV at a FOV at a seeing of 1.1seeing of 1.1”” along the line of sight. along the line of sight.

HAWKHAWK--I camera size: 4kI camera size: 4k××4k4k, 7.5, 7.5××7.5 arcmin, 0.1063 7.5 arcmin, 0.1063 arcsec/pixelarcsec/pixelWavefront tomography using 4 sodium Wavefront tomography using 4 sodium LGSsLGSs at 5.5 at 5.5 ‘‘ offoff--axisaxisFour ShackFour Shack--Hartmann WFS for Hartmann WFS for LGSsLGSs

40x40 40x40 subaperturessubapertures6x6 pixels per 6x6 pixels per subaperturesubaperture5 5 ““ FoVFoV per per subaperturesubaperture

Ground layer correction: one Deformable Secondary Mirror Ground layer correction: one Deformable Secondary Mirror (only solution!)(only solution!)High order loop High order loop framerateframerate > 500 Hz with 2 frames delay.> 500 Hz with 2 frames delay.offoff--axis visible tipaxis visible tip--tilt NGStilt NGS

R=14.5 for sky coverage 95%,e.g. 600 eR=14.5 for sky coverage 95%,e.g. 600 e--/frame (NB: R=12.5 /frame (NB: R=12.5 gives sky coverage of 50% at b=90gives sky coverage of 50% at b=90ºº))FramerateFramerate = 250Hz = 250Hz

One NGS WFS for DSM commissioning & maintenanceOne NGS WFS for DSM commissioning & maintenanceGLAO brings Seeing down from

0.8” to 0.6”Meaning 0.6” seeing 50% of time

“Site Improver”

| | | | | |0 0.17 0.5 0.84 1.2 1.7 (seeing arcsec J)


GRAAL onGRAAL on--sky guide stars geometrysky guide stars geometry

VIS TT NGSAcquisition FoV

7.5 arc-minutes

13,2 arc-minutes

15,2 arc-minutes

VIS TTNGS

LGS

LGS LGS

LGS

IR TTNGS

Pupil Rotation

Field Rotation

7.8 arc-minutes


GLAO as seeing reducer?GLAO as seeing reducer?

K Band, gain: 100% FWHM

Y Band,Gain: 30%

Seeing

With AO


GLAO improves Ensquared Energy?GLAO improves Ensquared Energy?

Y Band,gain: 50%

K Band, EE doubled

With AO

Seeing

Pixel: 0.1”


GLAO reduces confusion?GLAO reduces confusion?

K Band, gain: 30%

Y Band,Gain: 15%

Seeing

With AO


GLAO: useful for most astronomical programsGLAO: useful for most astronomical programs

Ground Layer Adaptive Optics = Seeing Ground Layer Adaptive Optics = Seeing ““reducerreducer””LGS and large LGS and large FoVFoV allows nearly full sky coverageallows nearly full sky coverageReduced Seeing => reduced exposure & telescope timesReduced Seeing => reduced exposure & telescope timesReduced seeing => Reduced confusion in Stellar populations & Reduced seeing => Reduced confusion in Stellar populations & Cluster fieldsCluster fields

Ground Layer Adaptive Optics = Seeing Ground Layer Adaptive Optics = Seeing ““stabilizerstabilizer””Seeing stabilizer => better percentile seeing for your site!Seeing stabilizer => better percentile seeing for your site!

Seeing reducer is Seeing reducer is ““easilyeasily”” achievable at all achievable at all λλss (down to (down to visvis.).)LGS and large LGS and large FoVFoV allow nearly full sky coverageallow nearly full sky coverageGLAO systems will to benefit most astronomical programsGLAO systems will to benefit most astronomical programs


Nasmyth instrumentNasmyth instrument24 spectrographs24 spectrographs

465 465 –– 930 nm930 nmR = 2000R = 2000--40004000400 400 MpixelsMpixels

Wide Field Mode (WFM)Wide Field Mode (WFM)11’’x1x1’’, 0.2, 0.2””/pix/pix>2x gain/pixel, <10% ct @ 2 pix>2x gain/pixel, <10% ct @ 2 pix(~0.3(~0.3”” gaussiangaussian PSF) PSF)

Narrow Field Mode (NFM)Narrow Field Mode (NFM)7.57.5””x7.5x7.5””, 0.025, 0.025”” /pix/pix1010--30% Strehl, < 10% crosstalk30% Strehl, < 10% crosstalk

Highlights of MUSEHighlights of MUSE


AO Facility: GALACSI for MUSEAO Facility: GALACSI for MUSE

GLAO and LTAO AO moduleGLAO and LTAO AO module4 4 WFSWFS’’ss. (40x40 sub. (40x40 sub--apertapert.) with L3 .) with L3

CCD, using 4 LGS CCD, using 4 LGS DichroicDichroic transmit 589nm light to WFS, transmit 589nm light to WFS,

and reflect and reflect visvis. for TT star. for TT star2x2 IR truth sensor for LTAO2x2 IR truth sensor for LTAONotch filter reduces MUSE backgroundNotch filter reduces MUSE backgroundPerformance ~2 more energy/pixel over Performance ~2 more energy/pixel over

11’’ (image concentration) (WFM)(image concentration) (WFM)StrehlStrehl >10% at 650 nm in 7>10% at 650 nm in 7”” (NFM)(NFM)


GALACSI Optical layout (WFM)GALACSI Optical layout (WFM)

Reimaging lensF/4.0

Field separator

Nas

myt

h Ad

apto

r fla

nge

4’ Field selector

VisibleTT

Sensor

1’ Optics free Scientific Field

CALIBRATIONMIRROR

LGS WFS

LGSWFS

LGS Focus compensation

LGS pick upLGS pick upExchangeable unit for NFMExchangeable unit for NFM

500 mm BFD500 mm BFD

180mm defocused Laser beam

1.45 arc min

Hole

FIELD SEPARATORTransmits 589nmReflects visible light

4 a

rc m

in

B.Delabre


GLAO performance: Sensitivity AnalysisGLAO performance: Sensitivity Analysis

Spot size Na thickness

Pupil shift

LGS return flux L3 CCD RON NGS brightness NGS loop framerate

LGS off-axis distance Number of corrected modes

Integrated seeing Ground seeing


Turbulence Vertical StructureTurbulence Vertical Structure

Seeing: 0.61”Alt.Layer: 0.29%τ0: 2.84.5 km: 36%9 km: 36%18 km: 28%

Seeing: 0.64”Alt.Layer: 0.28%τ0: 3.34.5 km: 14%9 km 38%18 km: 48%


LTAO performance: LGS position in LTAO performance: LGS position in FoVFoV

Baseline

Extremely sensitive for LTAO in VBut can be mitigated by optimized reconstruction


LTAO performance: uplink jitterLTAO performance: uplink jitter

• Need for local jitter control to reduce the residual amplitude• Need for a control of the non linear bias with a LB NGS WFS

Same amplitude on each axis

LT jitter conrol

WFS local jitter control

-3 -2 -1 0 1 2 3-3

-2

-1

0

1

2

3Effect of Tilt scan along X direction

Incoming Tilt in "

Mea

sure

d Ti

lt in

"

-8 -6 -4 -2 0 2 4 6 8-10

-8

-6

-4

-2

0

2

4

6

8

10Effect of Tilt scan along Y direction

Incoming Tilt in "

Mea

sure

d Ti

lt in

"

Bias induced by clipping

Non linearity induced by under-sampling


Control strategies: LGS issuesControl strategies: LGS issuesJitter loop: Jitter loop:

At the launch telescope for GRAALAt the launch telescope for GRAALIn front of the WFS for GALACSIIn front of the WFS for GALACSI

Fast low order NGS loop for tomography to identify the altitude Fast low order NGS loop for tomography to identify the altitude modes non modes non measurable by the LGS measurable by the LGS WFSsWFSs, due to Tip/Tilt indetermination , due to Tip/Tilt indetermination Focus loop to control the variation of Na altitude with a tromboFocus loop to control the variation of Na altitude with a trombone in front of ne in front of each LGS WFSeach LGS WFS

FeedFeed--forward term based on model to speedforward term based on model to speed--upupLocal term coming from each LGS WFS pseudoLocal term coming from each LGS WFS pseudo--static defocus to keep them static defocus to keep them working around 0working around 0NGS focus sensor to ensure the focusing of the scientific detectNGS focus sensor to ensure the focusing of the scientific detectororNa defocus residual WFE is ~ 50 nm Na defocus residual WFE is ~ 50 nm rmsrms for GLAO and 5 nm for GLAO and 5 nm rmsrms for LTAOfor LTAO

Control of nonControl of non--linear modes coming from WFS non linearity, Na thickness linear modes coming from WFS non linearity, Na thickness and LGS size variationand LGS size variation

Offset loop similar to focus loop but for higher order using a lOffset loop similar to focus loop but for higher order using a low bandwidth SH ow bandwidth SH WFS. The trombone actuation is equivalently replaced by offset sWFS. The trombone actuation is equivalently replaced by offset slopes for these lopes for these modes (~ 10)modes (~ 10)Online optimization of Online optimization of centroidingcentroiding maps and gains by system identificationmaps and gains by system identification


Control strategies: Control strategies: adaptive telescope issuesadaptive telescope issues

Pupil centering loop: Pupil centering loop: Based on IM obtained by closed loop system identificationBased on IM obtained by closed loop system identificationIM used to estimate pupil shift and distortionIM used to estimate pupil shift and distortionPupil shift controlled actively via DSM hexapod Pupil shift controlled actively via DSM hexapod

Active optics sensors are blind when M2 in closed loopActive optics sensors are blind when M2 in closed loopActive optics and guiding are Active optics and guiding are desactivateddesactivatedThe AO takes control of the telescope via offloadsThe AO takes control of the telescope via offloadsM2 Tip/Tilt to alt/M2 Tip/Tilt to alt/azaz axesaxesM2 defocus to hexapodM2 defocus to hexapodHigher order modes to M1Higher order modes to M1

No calibration source exists upstream the DMNo calibration source exists upstream the DMThe IM must be measured on sky or built syntheticallyThe IM must be measured on sky or built syntheticallyWe use a mix. Inputs of calibrated models into a pseudoWe use a mix. Inputs of calibrated models into a pseudo--synthetic IM generatorsynthetic IM generator

Acquisition strategy, overheads minimizationAcquisition strategy, overheads minimizationTelescope preset, bootstrap of active optics and all actuatorsTelescope preset, bootstrap of active optics and all actuatorsLGS acquisition loop to point it on the LGS LGS acquisition loop to point it on the LGS WFSsWFSsLaunch telescope bootstrap focus loopLaunch telescope bootstrap focus loopClose Jitter loopClose Jitter loopClose HO loopClose HO loopNGS acquisitionNGS acquisitionClose NGS loopClose NGS loopClose secondary loop (focus, non linear modes, pupil centering, Close secondary loop (focus, non linear modes, pupil centering, offloads, Instrument guidingoffloads, Instrument guiding……))

Overheads should be between 2 and 5 Overheads should be between 2 and 5 mnmn for each acquisitionfor each acquisition


/ with IM measured on calibration source

IM in MCAO: tests with MADIM in MCAO: tests with MAD

Pseudo-synthetic IMDifference “on sky” / pseudo-synthetic

Strehl map 2’ with IM “on sky”The IM measured on sky is slightly better than the artificially calibrated one The pseudoThe pseudo--synthetic IM underperforms rather significantly (>10%)synthetic IM underperforms rather significantly (>10%) -3

-2

-1

0

1

2DM0 ground

DM1 8,5 km

SH2SH1SH0


AOF acquisition strategyAOF acquisition strategy


CassegrainCassegrain Adaptive Simultaneous Imager System Adaptive Simultaneous Imager System CASIS?CASIS?

Courtesy B. Delabre


CASIS main specificationsCASIS main specificationsProvide good and uniform performance over a square Provide good and uniform performance over a square FoVFoV of 1 of 1 arcminutearcminute side, the scientific wavelength ranging from R to L side, the scientific wavelength ranging from R to L bandbandMean Mean strehlstrehl in K: spec 50%, goal 70%in K: spec 50%, goal 70%

MCAO system requiredMCAO system requiredGood spatial sampling: DSM with 1170 actuators + altitude Good spatial sampling: DSM with 1170 actuators + altitude DMsDMs and and LGS ShackLGS Shack--Hartmann with 20x20 to 40x40 elementsHartmann with 20x20 to 40x40 elements

Uniformity of the Uniformity of the strehlstrehl in the in the FoVFoV: 5% : 5% rmsrms2 altitude 2 altitude DMsDMs5 5 LGSsLGSs close to the scientific fieldclose to the scientific field

Sky coverage (attenuation of the performance by a factor 2): Sky coverage (attenuation of the performance by a factor 2): 70% at 30 degrees Galactic Latitude & 15% at Galactic Pole70% at 30 degrees Galactic Latitude & 15% at Galactic Pole

Use of LGS for the highUse of LGS for the high--order looporder loop3 Tip/Tilt sensor using 3 Tip/Tilt sensor using NGSsNGSs of magnitude < 19 to be found outside the of magnitude < 19 to be found outside the scientific scientific FoVFoV and within a disk of 3 and within a disk of 3 arcminutesarcminutes diameterdiameter


CASIS performanceCASIS performance

SCAO system for comparison

• 3 DM + 5 LGSs• seeing: 0.65”• 7 layers profile• high flux case• several performance points at the same radial distance


DM DM numbernumber vs vs sensedsensed modes modes numbernumber

3 DM

Courtesy ONERA


EffectEffect of the of the numbernumber of of LGSsLGSs

1.5‘1.5‘1.5‘1.5‘

• seeing: 0.75”• only 150 modes sensed with 20x20 subaperturesper Shack-Hartmann

Courtesy ONERA

s. oberti the eso adaptive optics department · clean room, beam diagnostic systems, lidar,...

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