GLAO simulations at ESO European Southern Observatory M. Le Louarn, Ch. Verinaud, V. Korkiakoski, N. Hubin European Southern Observatory

Summary of GLAO simulations @ESO Hawk-I (GRAAL) Large field (8’) Near IR (1-2.5 μm) Improved seeing, improved energy in pixel 4 Na-LGS MUSE (GALACSI) Moderate field (1’ -> 10’’) EE x 2 in 0.2’’ pixel or Diffraction limited (NFM) Visible (450 to 930 nm) OWL – GLAO/MOAO 3-6 NGSs Up to 6’ FOV or IFU GLAO as such (WF imaging ?) or first stage of MOAO

Atmosphere - HawkI GL r0=0.11 m at 0.5μm 0: 3.25 ms θ0=1.7’’ L0= 25m Turbulence Height (m) Fraction of Cn2 0.0000 0.334611 300.00 0.223074 900.00 0.111537 1800.0 0.09040635 4500.0 0.079603013 7100.0 0.05155671 11000. 0.04498746 12800. 0.0339061 14500. 0.0191147 16500. 0.0112030 GL r0=0.11 m at 0.5μm 0: 3.25 ms θ0=1.7’’ L0= 25m

PSF estimation stars 8’

AO parameters Muse NFM Hawaii 2 RG (?) Parameter Value Number of sub-apertures (linear) / LGS 32x32 Number of active sub-apertures / LGS 768 Active actuators 881 Number of LGS 4 Position of LGS 5.65’ off-axis (i.e. x=4’, y=4’) Flux from LGS 84 photons / sub-aperture / frame High order WFS frame rate 500 Hz Temporal delay 2 frames pure delay WFS CCD read-out noise 3 e- rms Loop gain 0.4 Position of NGS 2.8’ off-axis (x=2’,y=2’) Tip-tilt guide star flux ~115000 photons / sub-aperture / frame (K~10) Tip-tilt frame-rate 100 Hz Tip-tilt centroiding pixels 16x16 TT detector read-out noise 17 e- rms Wavelength 2.2 μm Seeing at 0.5 μm 0.94’’ Correlation time at 0.5 μm 3.25 ms Hawaii 2 RG (?)

EE in 0.1’’ pixel K Band Y Band

50% EE diameter K Band Y Band

FWHM (Gaussian fit) K Band Y Band

Different LGS config as previous slides Number of TT stars Peaks @ LGS locations 1 TT star Peaks @ TT stars 4 TT star Different LGS config as previous slides

Sub-aperture number (K band)

Single Rayleigh LGS On Axis R=1.4’ R=4’

Diamonds: seeing, stars: multi RLGS, crosses: Multi-Na LGS 4 Rayleigh LGS Diamonds: seeing, stars: multi RLGS, crosses: Multi-Na LGS

4 R LGS R-LGSs for GLAO as good as Na (or ~better) Cheap Decrease height to increase homogeneity Focusing problems ? (H ~ a few km) ? Spot elongation reduced (enough ?) by narrow gating Power req should be investigated Synchronization with WFSs must be dealt with Cheap No “synergy” with other LGS efforts @ ESO New designs required (launch telescopes ? Beam transfer ?)…

Hawk-I GLAO conclusions “Conventional GLAO” Gain in FWHM, telescope time (EE) Cn2 is a big unknown TT sensing scheme is still under study Hawaii 2 RG on-chip TT sensing seems promising. Use of narrow band filters might make things complicated Pick-off arms for TT are “ugly” !

Muse wide field performance Pixel size (arcseconds) Muse WFM On-axis and 0.5’ Off-axis 1.1’’ seeing

MUSE Narrow Field Mode on-axis : ~15% Median (0.65'') seeing Strehl Ratio @ 650nm on-axis : ~15% Median (0.65'') seeing Conditions Without error budget!

Muse Narrow field mode No Error budget 100 nm WFE 150 nm WFE See Hubin & al. For more on MUSE

Muse GLAO conclusions Muse explores a slightly different parameter space than “conventional GLAO” Visible light, high Strehl mode is challenging First attempt at Cone effect correction Drives ASM requirements + laser power req Calibration issues on ASM…

Simulations for ELTs Averaging control algorithm Average WFS measurements from N (3-6) stars Use much smaller control matrix Faster, less memory (good for simulations !) But not especially “clever” algorithm GLAO highly parallelizable for simulations Atmospheric propagations independent Each WFS runs separately On “small” (single star) matrix-vector multiplication Drawback: usually want stability in the field  many PSFs to compute  many (large) FFTs (but can be //-ized) Also used Cibola (Analytic, B. Ellerbroek) for rapid perf. estimation

OWL-GLAO Goal: Keep the same DM as in SCAO, (90x90 / 83x83) Improved seeing over ~6’ FOV K-Band Ground layer correction scheme Keep the same DM as in SCAO, (90x90 / 83x83) Use 3-6 Shack-Hartmann WFSs SH for GLAO: Linearity, no RON NGSs only for this study Located at the edges of 6’ FOV Performance estimation at FOV center

OWL-GL: Radial averaged profiles 10m 30m 60m 100m L0 effect like for seeing (R. Conan 03)

OWL GLAO (90x90), 0.5’’ seeing 6 NGS 3 NGS 10 ph /s /integ time

OWL GLAO (90x90), 50 mas, 0.8’’ Constellation edge 10 ph /s /integ time

1.9' (radius), mag 16, transmission 20%, GLAO vs seeing (100m) – 3 NGS K H J 1.9' (radius), mag 16, transmission 20%, 200 Hz, r0=0.15, 1m sub-apertures. Cibola

MOAO – (Falcon like) 3 NGS H J 1.9' (radius), mag 16, transmission 20%, 200 Hz, r0=0.15, 1m sub-apertures. Cibola

1.9' (radius), mag 16, transmission 20%, GLAO vs. MOAO 1.9' (radius), mag 16, transmission 20%, 200 Hz, r0=0.15, 1m sub-apertures.

OWL GLAO conclusions Woofer for MOAO seems mandatory (stroke issues of MEMs) MOAO provides better performance in small FOV Homogeneity of MOAO (in different IFUs must be studied) In GLAO, better PSF uniformity than on 8m Beam overlap gets better Performance not necessarily much better GLAO might constraints site for ELT

Conclusions Cn2 properties largely unknown (!) Statistics: Beginning vs. middle of night vs. end of night Variations within one night Seasonal variations Correlations “Good” seeing vs. “bad” seeing With wind direction (especially in Paranal) With other meteo Parameters SLODAR + MASS + DIMM running @ Paranal Balloon data unreliable for Paranal (site has changed significantly since campaign) NGS case: effect of in-equal NGS brightness  Optim modal gains being implemented for GLAO

Muse : Requirements Muse: Multi-Unit Spectroscopic Explorer 2 Modes: 24 4kx4k integral field spectrographs Very deep field spectroscopy 2 Modes: Wide Field Mode (WFM) 1’x1’ FOV from 450 nm to 930 nm 2 x EE of seeing in 0.2’’ pixel 1.1’’ seeing (80h integration times) Narrow Field Mode (NFM) ~10’’x10’’ FOV Diffraction limited (Sr(650nm)~10%) 25 mas pixels (?). 0.65’’ seeing Absolutely no scattered light in science field (WFM) High sky coverage (towards poles)

Muse: The AO 4 x High order (32x32) SH WFSs 4 Sodium LGSs high sky coverage (~60% at galactic poles, WFM) 2.5 – 5.0 106 ph/s/m2 Single high order DM conjugated to ground Ground-Layer AO (Rigaut 2002) 2 designs: with or without Adaptive secondary Visible (WFM) or IR (NFM) TT sensor Search field: 3’ (diam, WFM), 10’’ (diam, NFM) Repositionning of the LGSs to switch from WFM to NFM (cone effect correction).

TT correction only ? – K-band