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GLAO Workshop, Leiden; April 26 th 2005 Ground Layer Adaptive Optics, N. Hubin Ground Layer Adaptive Optics Status and strategy at ESO Norbert Hubin European.

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Presentation on theme: "GLAO Workshop, Leiden; April 26 th 2005 Ground Layer Adaptive Optics, N. Hubin Ground Layer Adaptive Optics Status and strategy at ESO Norbert Hubin European."— Presentation transcript:

1 GLAO Workshop, Leiden; April 26 th 2005 Ground Layer Adaptive Optics, N. Hubin Ground Layer Adaptive Optics Status and strategy at ESO Norbert Hubin European Southern Observatory With contributions from: R. Conzelman, B. Delabre, M. Le Louarn, S. Stroebele, R. Stuik, E. Vernet

2 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. HubinSCOPE  Is there a Ground Layer Adaptive Optics?  FAQ about GLAO and astronomical interest  VLT GLAOs: GALACSI and GRAAL projects  Adaptive secondary: an essential element of GLAO  Laser requirements, R&D status and issues  Optimization, calibration and testing of GLAO  Minimizing telescope down time during GLAO-DSM commissioning?

3 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. Hubin WHAT IS GROUND LAYER AO? WFSs Reference Stars Telescope High Altitude Layer Ground Layer DM conjugated Telescope pupil Real Time Computer Averaged WF.. Ground Layer Altitude Layers Laser beams

4 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. Hubin Ex: 50% of the time there is 55% OR LESS turbulence in the 1 st 500m More measurements are being carried out (M. Sarazin) Does a ground layer exist? PARANAL OBSERVATORY Courtesy: M. Sarazin

5 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. Hubin Turbulence Profile and ground layer Mauna Kea, October 22/23, 2002: G-scidar 0km 5km 10km 15km Data: J.Vernin, A.Ziad

6 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. Hubin Turbulence profile investigation tools Courtesy: M. Sarazin

7 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. Hubin Turbulence Profile and ground layer CERRO TOLOLO OBSERVATORY Courtesy: M. Sarazin R. Wilson

8 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. Hubin Turbulence Profile and ground layer CERRO TOLOLO OBSERVATORY Courtesy: M. Sarazin

9 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. Hubin Investigation of Ground layer at Paranal  Multi Aperture Scintillation Sensor MASS + DIMM: Cn2 profile  SLODAR: Slope Detection and ranging: Higher resolution of ground layer Courtesy: R. Wilson

10 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. Hubin GLAO as seeing reducer? VIS TT NGS Acquisition FoV 7.5 arc-minutes 13,2 arc-minutes 15,2 arc-minutes VIS TT NGS LGS IR TT NGS Pupil Rotation Field Rotation 7.8 arc-minutes Improved seeing, Sr(K) ~ 4% 8’ FOV SeeingPSF on-axisPSF off-axis Seeing reducer Reduced exposure & Telescope time Better light concentration Reduced confusion in Stellar populations & Cluster fields

11 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. Hubin GLAO as seeing reducer? VLT-GRAAL K Band, gain: 100% FWHM Y Band, Gain: 30% Seeing With AO

12 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. Hubin GLAO improves Ensquared Energy? VLT GRAAL Y Band, gain: 50% K Band, EE doubled With AO Seeing Pixel: 0.1”

13 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. Hubin GLAO reduces confusion?: VLT GRAAL K Band, gain: 40% Y Band, Gain: 30% Seeing With AO Yes but more difficult!

14 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. Hubin GLAO and full sky coverage?  Need Laser artificial stars for WFS tomography because of: Median to bad seeing conditions assumptions Median to bad seeing conditions assumptions Science performed down to short λ Science performed down to short λ  Require 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

15 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. Hubin GLAO in the visible?: VLT FOV=1’ GLAO Seeing Science 1’ FOV 4’ FOV 4 Sodium LGSs Ø120” Faint vis. TT-NGS

16 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. Hubin GLAO: useful for most astronomical programs  Ground Layer Adaptive Optics = Seeing reducer  Reduced Seeing => reduced exposure & telescope times  Reduced seeing => Reduced confusion in Stellar populations & Cluster fields  Ground Layer Adaptive Optics = Seeing “stabilizer”  Seeing stabilizer => better percentile seeing for your site!  Seeing reducer is “easily” achievable at all λs (down to vis.)  High Sky coverage GLAO systems will benefit most astronomical programs  Seeing reducer = light concentration: Sufficient for distant (“small”) galaxies with low surface brightness ( ” pixel enough)

17 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. Hubin VLT GLAO Top Level Requirements  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 required High sky coverage required Provide factor 2 EE improvement (0.2”) over 1’ FOV in [ ] Provide factor 2 EE improvement (0.2”) over 1’ FOV in [ ] Diffraction 750 nm over ~10’’ FOV=> LTAO! Diffraction 750 nm over ~10’’ FOV=> LTAO!  GRAAL: VLT-GLAO for an NIR Imager (HAWK-I) reduce by % in Y-Ks bands the diameter collecting 50% of the encircled energy (for seeing 1”) over 8’ FOV reduce by % in Y-Ks bands the diameter collecting 50% of the encircled energy (for seeing 1”) over 8’ FOV

18 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. Hubin GALACSI: Baseline concept  Wavefront tomography using 4 sodium LGSs  Four 32x32 subapertures Shack Hartmann WFS  Ground layer correction: one Deformable Mirror  Sodium notch filter to block the laser Rayleigh light  Off-axis visible tip-tilt NGS for Wide Field Mode  On-axis NIR tip-tilt NGS for Narrow Field Mode

19 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. Hubin GALACSI Narrow Field Mode Sr(R)~10% 4 Sodium LGSs Ø30” Faint NIR TT-NGS Science 7.5”FOV GALACSI Wide Field Mode EEx2 in 0.2” Science 1’ FOV 4’ FOV 4 Sodium LGSs Ø120” Faint vis. TT-NGS From GLAO to LTAO: Laser Tomography AO LTAO essentially correct for Laser cone effect within small FOV

20 European Southern Observatory European Southern Observatory © ESO 2005 Page 20 AO Department LYON, January 18/19th 2005 Reimaging lens F/4.0 Field separator Nasmyth Adaptor flange 4’ Field selector Visible TT Sensor 1’ Optics free Scientific Field LGS WFS LGS WFS LGS Focus compensation 500 mm BFD 180mm defocused Laser beam 1.45 arc min Hole FIELD SEPARATOR 4 arc min GALACSI: Ground Atmospheric Layer Adaptive Corrector for Spectroscopic Imaging Exchangeable unit for NFM See S. Stroebele talk`

21 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. Hubin GALACSI mechanical concept See S. Stroebele talk`

22 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. Hubin GLAO: Practical implementations GRAAL: GRound layer AO Assisted by Laser Goal: reduce by 15 % in Y and 30% in Ks band the diameter collecting 50% of the encircled energy (for 1”) over 7.5’ FOV Goal: reduce by 15 % in Y and 30% in Ks band the diameter collecting 50% of the encircled energy (for 1”) over 7.5’ FOV  HAWK-I camera size: 4k×4k, 7.5×7.5 arcmin, arcsec/pixel  Wavefront tomography using 4 sodium LGSs  Four Shack-Hartmann WFS for LGSs  Ground layer correction: one Deformable Secondary Mirror (only solution!)  On-axis NIR tip-tilt NGS using the HAWK-I detector  As alternative, off-axis visible tip-tilt NGS  One NGS WFS for DSM commissioning & maintenance

23 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. Hubin GRAAL on-sky guide stars geometry VIS TT NGS Acquisition FoV 7.5 arc-minutes 13,2 arc-minutes 15,2 arc-minutes VIS TT NGS LGS IR TT NGS Pupil Rotation Field Rotation 7.8 arc-minutes

24 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. Hubin GRAAL Functional Block Diagram WFS Calibration IR NGS TT Sensing Off-axis Vis NGS TT Sensor VLT ADAPTERVLT ADAPTER 4 LGS Wavefront sensors with LGS focus System HAWK-I HAWK-I Calibration 7.5’ FOV Pupil LGSs VLT M1 M2 +DM Laser Launch Telescopes Position 1 Pupil

25 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. Hubin CCD VIS TT Sensor Four 32x32 LGS WFSs 40x40 VIS NGS WFS DSM comm lenses unit Calibration fiber GRAAL: Opto-mechanical Design Rotating Structure to follow pupil rotation

26 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. Hubin Lenses DSM comm 40x40 VIS NGS WFS 32x32 LGS WFS VIS TT Sensor SKY HAWK-I Calibration fiber GRAAL Opto-mechanical Design

27 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. Hubin DSM commissioning & maintenance mode  40x40 subapertures Shack-Hartmann WFS  6x6 pixels per subaperture, pixel scale: 0.3 arcsec/pix  1.8 arcsec FOV per sub-aperture  Focal Elongator in front of HAWK-I  Pixel scale up to 10 milli arcsec/pixel 10 milli arcsec/pixel on a 10’’ FoV on a 10’’ FoV

28 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. Hubin Large FOV GLAO: The essential DSM VLT-Deformable Secondary Mirror  Full replacement unit  Ø 1.1m with 1170 act.  29 mm pitch  1 ms response  Total actuator stroke: ±40-50µm P-V  Total inter-actuator stroke: 1.3 µm P-V (goal 1.5  m PV)  Stroke resolution: 5 nm VLT-DSM

29 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. Hubin ACTUATORS SEPARATION 28.5 < Dist. < 29.6 VLT DSM Actuator Pattern

30 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. Hubin Large Deformable mirror design Reference plate Heat-sink and act. support plate Electronics boxes deformable shell: 2mm! Central membrane for lateral support

31 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. Hubin Laser Guide Star Requirements  Photon flux: at least 1.5x10 6 Na photons/m 2 /s (goal 2.5x10 6 )  LGS pointing range up to 5.5 arcmin / VLT optical axis  Max. spot size of 1.25arcsec FWHM at 45 degrees from Zenith  Absolute LGS pointing precision in open loop: 1.1” (goal 0.5”)  Total residual jitter smaller than 50 mas rms  Output power stability: <1 % on a 10 ms time scale, <15 % on longer time scales (days)

32 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. Hubin 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

33 Ground Layer AO, N. Hubin33 ESO Fibre Raman laser demonstrator setup 1178 nm, 0.75 GHz fibre Raman seed laser Fibre Raman pre-amplifier Fibre Raman booster amplifier Diode-pumped 1121-nm Yb-doped fibre pump laser Bulk 2nd-harmonic generation in periodically-poled KTP crystal 589 nm, 1.5 GHz Courtesy: D. Bonaccini W. Hackenberg

34 Ground Layer AO, N. Hubin34 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 linewidth PPKTP, 30mm long used for SHG from 1178 to 589nm Courtesy: D. Bonaccini W. Hackenberg

35 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. Hubin Rayleigh scattering and “Fratricide” effect  Simulated for large field  WFS cut a small section  4 LGS  Launch behind M2  Pointing 60“ off axis  Subaperture pos. (0, -1) [m] View of one individual sub aperture

36 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. Hubin Optimization and calibration aspects Optimization of WFS square –DSM circular geometry Influence functions optimization Synthetic versus on-sky interaction matrix?

37 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. Hubin GLAO-DSM laboratory testing facility 3D Turbulence generator 2’ FOV Optical corrector ~1.7 m Spherical mirror 1.1m Adaptive secondary 4’ Field selector Visible TT Sensor LGS WFS LGS WFS Full testing of DSM and GLAO facility before installation at the VLT!! GALACSI

38 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. Hubin GLAO as 1 st 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

39 GLAO Workshop, Leiden; April 26 th 2005Ground Layer AO, N. HubinConclusions  GLAO is: a seeing reducer & stabilizer at all λ and essentially gives access to a better site a seeing reducer & stabilizer at all λ and essentially gives access to a better site improves Ensquared Energy, reduce confusion and reduce telescope time improves Ensquared Energy, reduce confusion and reduce telescope time if designed for full sky coverage will impact most of astronomical fields if designed for full sky coverage will impact most of astronomical fields  GRAAL for large FOV in NIR  GALACSI for 1’ FOV correction in the visible  GALACSI with Laser reconfiguration provides LTAO correction  Large DM and LGSs are essential for GLAO  Intensive calibration & testing essential for on-site robust operation  GLAO is an important 1 st stage corrector for FALCON or MCAO  GRAAL-GALACSI-DSM-LGSF4: a VLT Facility? => ESO Facility design review: end 05


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