glao workshop, leiden; april 26 th 2005 ground layer adaptive optics, n. hubin ground layer adaptive...

GLAO Workshop, Leiden; April 26GLAO Workshop, Leiden; April 26thth 2005 2005 Ground Layer Adaptive Optics, N. HubinGround Layer Adaptive Optics, N. Hubin

Ground Layer Adaptive OpticsGround Layer Adaptive OpticsStatus and strategy at ESOStatus and strategy at ESO

Norbert HubinNorbert HubinEuropean Southern ObservatoryEuropean Southern Observatory

With contributions from:With contributions from:R. Conzelman, B. Delabre, M. Le Louarn, S. R. Conzelman, B. Delabre, M. Le Louarn, S.

Stroebele, R. Stuik, E. VernetStroebele, R. Stuik, E. Vernet

GLAO Workshop, Leiden; April 26GLAO Workshop, Leiden; April 26thth 2005 2005 Ground Layer AO, N. HubinGround Layer AO, N. Hubin

SCOPESCOPE

Is there a Ground Layer Adaptive Optics?Is there a Ground Layer Adaptive Optics? FAQ about GLAO and astronomical interestFAQ about GLAO and astronomical interest VLT GLAOs: GALACSI and GRAAL projectsVLT GLAOs: GALACSI and GRAAL projects Adaptive secondary: an essential element of GLAOAdaptive secondary: an essential element of GLAO Laser requirements, R&D status and issuesLaser requirements, R&D status and issues Optimization, calibration and testing of GLAOOptimization, calibration and testing of GLAO Minimizing telescope down time during GLAO-DSM Minimizing telescope down time during GLAO-DSM

commissioning?commissioning?


WHAT IS GROUND LAYER AO?WHAT IS GROUND LAYER AO?

WFSs

Reference Stars

Telescope

High Altitude Layer

Ground Layer

DM conjugatedTelescope pupil Real Time Computer

Averaged WF..Ground Layer

AltitudeLayers

Laserbeams

GLAO Workshop, Leiden; April 26GLAO Workshop, Leiden; April 26thth 2005 2005 Ground Layer AO, N. HubinGround Layer AO, N. HubinEx: 50% of the time there is 55% OR LESS turbulence in the 1st 500mMore measurements are being carried out (M. Sarazin)

Does a ground layer exist?Does a ground layer exist?

PARANAL OBSERVATORY

Courtesy: M. Sarazin


Turbulence Profile and ground layerTurbulence Profile and ground layer

Mauna Kea, October 22/23, 2002: G-scidarMauna Kea, October 22/23, 2002: G-scidar

0km

5km

10km

15km

Data: J.Vernin, A.Ziad


Turbulence profile investigation toolsTurbulence profile investigation tools




CERRO TOLOLO OBSERVATORY

Courtesy: M. SarazinR. Wilson



CERRO TOLOLO OBSERVATORY



Investigation of Ground layer at ParanalInvestigation of Ground layer at Paranal

Multi Aperture Scintillation Sensor MASS + DIMM: Cn2 profileMulti Aperture Scintillation Sensor MASS + DIMM: Cn2 profile SLODAR: Slope Detection and ranging: Higher resolution of SLODAR: Slope Detection and ranging: Higher resolution of

ground layerground layer

Courtesy: R. Wilson


GLAO as seeing reducer?GLAO as seeing reducer?

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

Improved seeing, Sr(K) ~ 4% 8’ FOV

Seeing PSF on-axis PSF off-axis

Seeing reducer

Reduced exposure & Telescope time

Better light concentration

Reduced confusion in Stellar populations & Cluster fields


GLAO as seeing reducer? VLT-GRAALGLAO as seeing reducer? VLT-GRAAL

K Band, gain: 100% FWHM

Y Band,Gain: 30%

Seeing

With AO


GLAO improves Ensquared Energy? VLT GRAALGLAO improves Ensquared Energy? VLT GRAAL

Y Band,gain: 50%

K Band, EE doubled

With AO

Seeing

Pixel: 0.1”


GLAO reduces confusion?: VLT GRAALGLAO reduces confusion?: VLT GRAAL

K Band, gain: 40%

Y Band,Gain: 30%

Seeing

With AO

Yes but more difficult!


GLAO and full sky coverage?GLAO and full sky coverage?

Need Laser artificial stars for WFS tomography because of:Need Laser artificial stars for WFS tomography because of: Median to bad seeing conditions assumptionsMedian to bad seeing conditions assumptions Science performed down to short Science performed down to short λλ

Require Natural Guide Star for Tip-tilt correctionRequire Natural Guide Star for Tip-tilt correction

Tip-tilt limiting magnitude (R-Band)Probability for (top to bottom) 1,2,3 TT NGS

In 1arcmin annular FOV

Tip-tilt limiting magnitude (R-Band)Probability for (top to bottom) 1,2,3 TT NGS

In 2 arcmin annular FOV

1 VIS NGS


GLAO in the visible?: VLT GALACSIGLAO in the visible?: VLT GALACSI

@750nm; FOV=1’

GLAO

Seeing

Science 1’ FOV

4’ FOV

4 Sodium LGSsØ120”

Faint vis. TT-NGS


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

Ground Layer Adaptive Optics = Seeing reducerGround Layer Adaptive Optics = Seeing reducer Reduced Seeing => reduced exposure & telescope timesReduced Seeing => reduced exposure & telescope times Reduced seeing => Reduced confusion in Stellar Reduced seeing => Reduced confusion in Stellar

populations & Cluster fieldspopulations & Cluster fields Ground Layer Adaptive Optics = Seeing “stabilizer”Ground Layer Adaptive Optics = Seeing “stabilizer” Seeing stabilizer => better percentile seeing for your site!Seeing stabilizer => better percentile seeing for your site! Seeing reducer is “easily” achievable at all Seeing reducer is “easily” achievable at all λλss (down to vis.) (down to vis.) High Sky coverage GLAO systems will benefit most High Sky coverage GLAO systems will benefit most

astronomical programsastronomical programs Seeing reducer = light concentration: Sufficient for distant Seeing reducer = light concentration: Sufficient for distant

(“small”) galaxies with low surface brightness (0.2-0.1” (“small”) galaxies with low surface brightness (0.2-0.1” pixel enough)pixel enough)


VLT GLAO Top Level RequirementsVLT GLAO Top Level Requirements

GALACSI: VLT-GLAO for a Visible 3D Spectro (MUSE):GALACSI: VLT-GLAO for a Visible 3D Spectro (MUSE): Very deep exposures (80 h) =>NGSs in Scientific FOV forbidden !Very deep exposures (80 h) =>NGSs in Scientific FOV forbidden ! Statistically BAD seeing (1.1’’)Statistically BAD seeing (1.1’’) High sky coverage requiredHigh sky coverage required Provide factor 2 EE improvement (0.2”) over 1’ FOV in [450-930]Provide factor 2 EE improvement (0.2”) over 1’ FOV in [450-930] Diffraction limited @ 750 nm over ~10’’ FOV=> Diffraction limited @ 750 nm over ~10’’ FOV=> LTAO!LTAO!

GRAAL: VLT-GLAO for an NIR Imager (HAWK-I)GRAAL: VLT-GLAO for an NIR Imager (HAWK-I) reduce by 15-30 % in Y-Ks bands the diameter collecting 50% of reduce by 15-30 % in Y-Ks bands the diameter collecting 50% of

the encircled energy (for seeing 1”) over 8’ FOVthe encircled energy (for seeing 1”) over 8’ FOV


GALACSI: Baseline conceptGALACSI: Baseline concept

Wavefront tomography using 4 sodium LGSsWavefront tomography using 4 sodium LGSs Four 32x32 subapertures Shack Hartmann WFSFour 32x32 subapertures Shack Hartmann WFS Ground layer correction: one Deformable MirrorGround layer correction: one Deformable Mirror Sodium notch filter to block the laser Rayleigh lightSodium notch filter to block the laser Rayleigh light Off-axis visible tip-tilt NGS for Wide Field ModeOff-axis visible tip-tilt NGS for Wide Field Mode On-axis NIR tip-tilt NGS for Narrow Field ModeOn-axis NIR tip-tilt NGS for Narrow Field Mode


GALACSI Narrow Field ModeGALACSI Narrow Field ModeSr(R)~10%Sr(R)~10%


Faint NIR TT-NGSScience

7.5”FOV

GALACSI Wide Field ModeGALACSI Wide Field ModeEEx2 in 0.2”EEx2 in 0.2”

Science 1’ FOV

4’ FOV


Faint vis. TT-NGS

From GLAO to LTAO: Laser Tomography AOFrom GLAO to LTAO: Laser Tomography AO

LTAO essentially correct for Laser cone effect within small FOV

LYON, January 18/19th 2005LYON, January 18/19th 2005

EuropeanSouthernObservatory

EuropeanSouthernObservatory

© ESO 2005© ESO 2005Page 20 AO DepartmentAO Department

Reimaging lens F/4.0

Field separator

Nasm

yth

Adap

tor

flang

e

4’ Field selector

VisibleTT

Sensor

1’ Optics free Scientific Field

LGS WFS

LGS WFS

LGS Focus compensation

500 mm BFD500 mm BFD

180mm defocused Laser beam

1.45 arc min

Hole

FIELD SEPARATOR

4 a

rc m

in

GALACSI: Ground Atmospheric Layer Adaptive Corrector for Spectroscopic Imaging

Exchangeable unit for NFMExchangeable unit for NFM

See S. Stroebele talk`


GALACSI mechanical conceptGALACSI mechanical concept

See S. Stroebele talk`


GLAO: Practical implementationsGLAO: Practical implementationsGRAAL: GRAAL: GRGRound layer ound layer AAO O AAssisted by ssisted by 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 (for 1”) over 7.5’ FOVcollecting 50% of the encircled energy (for 1”) over 7.5’ FOV

HAWK-I camera size: 4kHAWK-I camera size: 4k×4k×4k, 7.5, 7.5×7.5 arcmin, 0.1063 arcsec/pixel×7.5 arcmin, 0.1063 arcsec/pixel Wavefront tomography using 4 sodium LGSsWavefront tomography using 4 sodium LGSs Four Shack-Hartmann WFS for LGSsFour Shack-Hartmann WFS for LGSs Ground layer correction: one Deformable Secondary Mirror (only Ground layer correction: one Deformable Secondary Mirror (only

solution!)solution!) On-axis NIR tip-tilt NGS using the HAWK-I detectorOn-axis NIR tip-tilt NGS using the HAWK-I detector As alternative, off-axis visible tip-tilt NGSAs alternative, off-axis visible tip-tilt NGS One NGS WFS for DSM commissioning & maintenanceOne NGS WFS for DSM commissioning & maintenance


GRAAL on-sky guide stars geometryGRAAL on-sky 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


GRAAL Functional Block DiagramGRAAL Functional Block Diagram

WFS Calibration

IR NGS TT

Sensing

Off-axis Vis NGS

TT Sensor

VLT

ADAPTER

4 LGS Wavefront

sensors withLGS focus

System

HAWK-I

HAWK-I Calibration

7.5’ FOV

Pupil

LGSs

VLT M1

M2 +DM

Laser LaunchTelescopesPosition 1

Pupil


CCD VIS TT Sensor

Four 32x32 LGS WFSs

40x40 VIS NGS WFS

DSM comm lenses unit

Calibration fiber

GRAAL: Opto-mechanical DesignGRAAL: Opto-mechanical Design

Rotating Structure to follow pupil rotation


Lenses DSM comm

40x40 VIS NGS WFS

32x32 LGS WFS

VIS TT Sensor

SKY HAWK-I

Calibration fiber

GRAAL Opto-mechanical DesignGRAAL Opto-mechanical Design


DSM commissioning & maintenance modeDSM commissioning & maintenance mode

40x40 subapertures Shack-Hartmann WFS40x40 subapertures Shack-Hartmann WFS 6x6 pixels per subaperture6x6 pixels per subaperture, pixel scale: 0.3 arcsec/pix, pixel scale: 0.3 arcsec/pix 1.8 arcsec FOV per sub-aperture1.8 arcsec FOV per sub-aperture Focal Elongator in front of HAWK-IFocal Elongator in front of HAWK-I Pixel scale up to Pixel scale up to

10 milli arcsec/pixel 10 milli arcsec/pixel

on a 10’’ FoVon a 10’’ FoV

15:29:24

Scale: 0.80 26-Oct-04

31.25 MM


Large FOV GLAO: The essential DSMLarge FOV GLAO: The essential DSM

VLT-Deformable Secondary MirrorVLT-Deformable Secondary MirrorFull replacement unitFull replacement unitØ Ø 1.1m with 1170 act.1.1m with 1170 act. 29 mm pitch29 mm pitch 1 ms response1 ms responseTotal actuator stroke: ±40-50µm P-VTotal actuator stroke: ±40-50µm P-VTotal inter-actuator stroke: 1.3 µm P-Total inter-actuator stroke: 1.3 µm P-V (goal 1.5V (goal 1.5m PV)m PV)Stroke resolution: 5 nmStroke resolution: 5 nm

VLT-DSMVLT-DSM


ACTUATORS SEPARATION

28.5 < Dist. < 29.6

VLT DSM Actuator PatternVLT DSM Actuator Pattern


Large Deformable mirror designLarge Deformable mirror design

Reference plateHeat-sink and act.support plate

Electronics boxes

deformable shell: 2mm!

Central membranefor lateral support


Laser Guide Star RequirementsLaser Guide Star Requirements

Photon flux: at least Photon flux: at least 1.5x101.5x1066 Na photons/m Na photons/m22/s (goal 2.5x10/s (goal 2.5x1066) ) LGS pointing range up to 5.5 arcmin / VLT optical axisLGS pointing range up to 5.5 arcmin / VLT optical axis Max. spot size of 1.25arcsec FWHM at 45 degrees from Max. spot size of 1.25arcsec FWHM at 45 degrees from

ZenithZenith Absolute LGS pointing precision in open loop: 1.1” (goal Absolute LGS pointing precision in open loop: 1.1” (goal

0.5”)0.5”) Total residual jitter smaller than 50 mas rmsTotal residual jitter smaller than 50 mas rms Output power stability: Output power stability: <1 % on a 10 ms time scale, <15 % <1 % on a 10 ms time scale, <15 %

on longer time scales (days)on longer time scales (days)


ESO’s fibre laser programme

• For next generation LGS-AO systems and MCAO, ESO’s strategy is to develop ~1 GHz 15 W CW*) fiber lasers at 589 nm, together with industry

• This strategy has created a collaboration agreement with LLNL to develop a sum-frequency fiber laser and an internal effort on fiber Raman laser/amplifier for which we ask support to the EU funding schemes*)The design also allows a pulsed laser output format if needed

Courtesy: D. Bonaccini W. Hackenberg

Ground Layer AO, N. HubinGround Layer AO, N. Hubin 3333

ESO Fibre Raman laser demonstrator setup

1178 nm, 0.75 GHzfibre Raman

seed laser

Fibre Ramanpre-amplifier

Fibre Ramanbooster amplifier

Diode-pumped 1121-nm Yb-doped fibre pump laser

Bulk 2nd-harmonic generation in periodically-poled KTP crystal

589 nm, 1.5 GHz


Ground Layer AO, N. HubinGround Layer AO, N. Hubin 3344

First 589-nm light with the frequency-doubled fibre Raman laser demonstrator in Oct ‘04

• achieved 150 mW CW at 589-

nm

• diffraction-limited output

beam

• 1.5 GHz linewidthPPKTP, 30mm long used for SHG from 1178 to 589nm



Rayleigh scattering and “Fratricide” effectRayleigh scattering and “Fratricide” effect

-80 -60 -40 -20 0 20 40 60 80

-80

-60

-40

-20

0

20

40

60

80

field position ["]

field

pos

ition

["]

View of 1 subap. "Big WFS" Simulated for large fieldWFS cut a small section4 LGSLaunch behind M2Pointing 60“ off axisSubaperture pos. (0, -1) [m]

View of one individual sub aperture


Optimization and calibration aspectsOptimization and calibration aspects

10 20 30 40 50 60

10

20

30

40

50

6010 20 30 40 50 60

10

20

30

40

50

60

IM on beacon IM on sky

Interaction matrices measured on MACAO UT4with a membrane stroke of 10% and a DM stroke of 4%On sky, the seeing was 0.63" and the T0 2.3 ms

• Optimization of WFS square –DSM circular geometry• Influence functions optimization• Synthetic versus on-sky interaction matrix?•


GLAO-DSM laboratory testing facilityGLAO-DSM laboratory testing facility

3D Turbulence generator

2’ FOVOpticalcorrector

~1.7 m Spherical mirror

1.1m Adaptive secondary

4’ Field selector

VisibleTT

Sensor

LGS WFS

LGS WFS

Full testing of DSM and GLAO facilitybefore installation at the VLT!!GALACSI


GLAO as 1GLAO as 1stst stage for FALCON-MCAO stage for FALCON-MCAO

multi-IFUs

3WFS/IFU

GLAO as a first stage for FALCON-MOAO concept Correct ground layer over a large FOV ~ concept of Woofer DM Reduce stroke requirements for the local corrector (MEMS) Optimum use of the numerous WFSs needed for multi-IFU

GLAO is a natural 1st stage for MCAO system


ConclusionsConclusions

GLAO is:GLAO is: a seeing reducer & stabilizer at all a seeing reducer & stabilizer at all λλ and essentially gives access to a better site and essentially gives access to a better site improves Ensquared Energy, reduce confusion and reduce telescope timeimproves Ensquared Energy, reduce confusion and reduce telescope time if designed for full sky coverage will impact most of astronomical fieldsif designed for full sky coverage will impact most of astronomical fields

GRAAL for large FOV in NIRGRAAL for large FOV in NIR GALACSI for 1’ FOV correction in the visibleGALACSI for 1’ FOV correction in the visible GALACSI with Laser reconfiguration provides LTAO correction GALACSI with Laser reconfiguration provides LTAO correction Large DM and LGSs are essential for GLAOLarge DM and LGSs are essential for GLAO Intensive calibration & testing essential for on-site robust operationIntensive calibration & testing essential for on-site robust operation GLAO is an important 1GLAO is an important 1stst stage corrector for FALCON or MCAO stage corrector for FALCON or MCAO GRAAL-GALACSI-DSM-LGSF4: a VLT Facility? GRAAL-GALACSI-DSM-LGSF4: a VLT Facility?

=> ESO Facility design review: end 05=> ESO Facility design review: end 05

glao workshop, leiden; april 26 th 2005 ground layer adaptive optics, n. hubin ground layer adaptive...

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