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MAORY Multi conjugate Adaptive Optics RelaY for the E-ELT Emiliano Diolaiti (INAF–Osservatorio Astronomico di Bologna) On behalf of the MAORY Consortium INAF + University of Bologna ONERA ESO AO for ELT – Paris, 22-26 June 2009 http://www.bo.astro.it/~maory Concept Corrected field of view – Central 53"x53" unvignetted for MICADO – Outer field Ø=160" for Natural Guide Star search and other instruments Wavefront sensing – 6 Sodium Laser Guide Stars for high-order wavefront measurement – 3 Natural Guide Stars for low-order and windshake measurement – 1 Natural Guide Star used as high-order reference WFS Wavefront correction – Telescope M4 + M5 – 2 post-focal deformable mirrors – Simplified option with 1 post-focal DM and reduced outer field under study AO for ELT – Paris, 22-26 June 2009 2 Two ports 1) gravity invariant w/ field derotation 2) vertical w/o field derotation Preliminary bench size: 6335 mm 6755 mm Preliminary mass estimate: 13 t See poster by Italo Foppiani AO for ELT – Paris, 22-26 June 2009 3 Optical design M13 M9 R = 10 m K = -0.87 D = 0.9 m R = 9.8 m K = -0.91 D = 1.1 m M7 R = 10 m K = -0.87 D=1m M8 M11 DM @4km D = 370 ~45 act/D R = 9,.8 m K = -0.91 D = 0.9 m M10 Flat D = 0.9 m M12 DM @12.7km D = 414 mm ~52 act./D AO for ELT – Paris, 22-26 June 2009 To LGS channel M13 R = 10 m K = -0.87 D = 0.9 m Field Ø160" WFE 25 nm Distortion < 0.1% Field curvature R = 1.3m 4 LGS optics and aberrations L1 L2 L3 L4 D = 800 mm D = 700 mm D = 580 mm D = 460 mm Dichroic 200 km 80 km 350 mm Design features – All lenses made of BK7, spherical surfaces (with wedge) – Output focus F/5, telecentric Image quality – LGS spot FWHM 0.17 arcsec (LGS image through atmosphere 1.5 arcsec) – RMS WFE 2.6 (average for 6 LGS) SH WFS slope offset 0.5 arcsec Solutions to LGS aberrations – Correcting optics (likely not static) in each LGS probe – Handled as slope offset Pupil stabilization and jitter control to be implemented in each LGS probe AO for ELT – Paris, 22-26 June 2009 5 Thermal emission Requirement on thermal emission < 50% (telescope + sky) @ K No cooling for T < 30C No cooling for T < 16C Telescope emissivity = 10% Sky brightness K = 13 mag/arcsec2 Emissivity of MAORY optics = 1% per surface (left) or 2% per surface (right) Requirement seems to be fulfilled at ambient temperature Paranal average temperature year 2003 (highest average 1985-2006): T = (13.12.6) C (from http://www.eso.org/gen-fac/pubs/astclim/paranal/temperature/) AO for ELT – Paris, 22-26 June 2009 6 Pupil rotations Baseline – – – How do things move in this scheme? – – – LGS fixed wrt telescope Post-focal DMs derotated by 60° (30°) LGS WFS probes derotated by 60° (30°) All DMs (M4 and post-focal) appear fixed wrt LGS WFS Pupil rotates wrt post-focal NGS WFS at maximum speed ~15/s for a Zenith angle of 1°. Reconstruction matrix of low order modal loop to be updated every 10s High order loop reconstruction matrix (25GB of data) must be updated every 140s (LGS footprint variation) Alternatives – – Post-focal DMs cannot be derotated reconstruction matrix to be updated every 35s LGS fixed wrt sky reconstruction matrix to be updated every 0.5s AO for ELT – Paris, 22-26 June 2009 7 LGS Wavefront Sensor Weighted Center of Gravity Photons / subap = 500, RON = 3 Subaperture FoV = 15"15" WCoG vs. Quad-cell 0.75 "/pixel 1.0 "/pixel 1.5 "/pixel 0.75 "/pixel 1.0 "/pixel – – – 1.5 "/pixel Non linearity AO for ELT – Paris, 22-26 June 2009 Evaluation of algorithms performance for SH WFS Poster by Matteo Lombini WFS noise Impact of Sodium profile LGS aberrations Alternative WFS – – Pyramid (smaller detectors) Dynamic refocus (by segmented mirrors on sub-pupils?) 8 Focus reconstruction scheme F(θ6) + Na F(θ) F(θ5) + Na F(θ1) + Na F(θ4) + Na F(θ2) + Na F(θ3) + Na Sodium focus sequence on 42 m aperture Requires NGS reference 6 LGS measure atmospheric + Sodium focus Used to “predict” focus in direction of NGS Comparison of predicted NGS focus with actual focus gives Sodium term AO for ELT – Paris, 22-26 June 2009 9 NGS Wavefront Sensor NGS measured in IR benefit from high-order loop correction Baseline H band T = 5 ms Windshake is the most challenging issue for tip-tilt. After feedback on telescope main axes a residual jitter ~0.3 RMS is expected. Making use of a predictive control filter (like Kalman) it may be drastically reduced exploiting its high temporal correlation (low frequency components) AO for ELT – Paris, 22-26 June 2009 Target WFE = 100 nm (3 NGS) 4 mas residual jitter per NGS 4-5 mas/pixel, 1"1" FoV at least 256256 pixels detector required. This is 2 the foreseen high speed IR sensor by Teledyne (128128, 5e- RON @900Hz, J. Beletic, SPIE 2008 Marseille) 10 MCAO tomography More details by Jean-Marc Conan and Clélia Robert Tomography performed by – 6 LGS, launched from M1 edge, kept fixed with telescope to relax requirements on RTC. LGS FoV = 2' – 3 NGS for low-orders reconstruction Star oriented architecture Point source at infinity WFS1 WFS2 WFS3 LGS HLGS LGS off-axis angle a FoV/2 D AO for ELT – Paris, 22-26 June 2009 11 Error sources Item RMS WFE MCAO (High order) 255 nm Generalized fitting + tomography LGS WFS noise Generalized aliasing Temporal error 232 nm 77 nm 41 nm 60 nm NGS WFS 100 nm NGS WFS noise and time delay 100 nm Implementation errors Estimated by “Fourier” code + cone effect degradation factor Input to NGS WFS design and sky coverage estimation 140 nm Optics (including non-common path errors) Deformable mirrors AO control Sodium layer Atmosphere TOTAL Top level allocations 308 nm Current PSF estimates include MCAO error budget Other error sources included in Strehl Ratio and Encircled Energy End-to-end simulations ready soon More details on simulations by Cyril Petit AO for ELT – Paris, 22-26 June 2009 12 Strehl Ratio NGS search field AO for ELT – Paris, 22-26 June 2009 13 Encircled Energy (0.8" seeing) 500 mas 200 mas 75 mas 50 mas AO for ELT – Paris, 22-26 June 2009 14 Performance & Sky coverage Nominal average performance over MICADO field of view (53"53") Seeing @0.5 µm Strehl Ratio % Ks (2.16 µm) H (1.65 µm) J (1.215 µm) Y (1.021 µm) I (0.9 µm) 0.8" 53.1 33.8 13.6 6.0 2.7 0.6" 60.7 42.5 20.7 10.7 5.7 Sky coverage at North Galactic Pole (L0 = 25m, windshake included) 3 NGS (2 Tip-Tilt, 1 Tip-Tilt & Focus) measured at H band, NGS search field Ø = 2.5‘ Sky cov. estimated by Monte Carlo simulations of asterisms based on TRILEGAL code Seeing @0.5 µm 0.8" 0.6" Minimum field-averaged Strehl Ratio Probability Ks (2.16 µm) H (1.65 µm) J (1.215 µm) Y (1.021 µm) I (0.9 µm) 53.1 33.8 13.6 6.0 2.7 26% 47.8 28.2 9.7 3.7 1.5 38% 41.2 21.9 6.1 1.9 0.6 48% 60.7 42.5 20.7 10.7 5.7 33% 54.6 35.4 14.8 6.6 3.1 48% 47.1 27.5 9.3 3.4 1.3 57% AO for ELT – Paris, 22-26 June 2009 15 PSF modeling for scientific analysis Simulated PSF Strehl Ratio 0.6 Image size = 2.7" PSF model Model components Airy DIFFRACTION AO for ELT – Paris, 22-26 June 2009 Hexagonal Moffat Moffat FITTING ERRORS, UNSEEN MODES Moffat SEEING 16 Acknlowledgment The activities outlined in this talk were partially funded by the European Community under the following grants: – Framework Programme 6, ELT Design Study, contract No 011863 – Framework Programme 7, Preparing for the Construction of the European Extremely Large Telescope, contract No INFRA2007-2.2.1.28 AO for ELT – Paris, 22-26 June 2009 17