MAORY Multi conjugate Adaptive Optics RelaY for the EELT

1
MAORYMulti conjugate Adaptive Optics RelaY for
the E-ELT

• Emiliano Diolaiti (INAFOsservatorio Astronomico
  di Bologna)
• On behalf of the MAORY Consortium

INAF University of Bologna ONERA ESO
http//www.bo.astro.it/maory
2
Concept

• Corrected field of view
• Central 53"x53" unvignetted for MICADO
• Outer field Ø160" 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

3
Two ports1) gravity invariant w/ field
derotation2) vertical w/o field
derotation Preliminary bench size 6335 mm ?
6755 mm Preliminary mass estimate 13 t
See poster by Italo Foppiani
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Optical design
M9 R 9.8 m K -0.91 D 1.1 m
M13 R 10 m K -0.87 D 0.9 m
M7 R 10 m K -0.87 D 1 m
M11 R 9,.8 m K -0.91 D 0.9 m
M8 DM _at_4km D 370 45 act/D
M10 Flat D 0.9 m
To LGS channel
Field Ø160" WFE ? 25 nm Distortion lt 0.1 Field
curvature R 1.3m
M12DM _at_12.7km D 414 mm 52 act./D
M13 R 10 m K -0.87 D 0.9 m
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LGS optics and aberrations
L1 D 800 mm
L2D 700 mm
L3D 580 mm
L4D 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

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Thermal emission
Requirement on thermal emission lt 50 (telescope
sky) _at_ K
No cooling for T lt 30?C
No cooling for T lt 16?C
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 (13.1?2.6) ?C
(from http//www.eso.org/gen-fac/pubs/astclim/par
anal/temperature/)
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Pupil rotations

• Baseline
• LGS fixed wrt telescope
• Post-focal DMs derotated by 60 (?30)
• LGS WFS probes derotated by 60 (?30)
• How do things move in this scheme?
• 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

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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

• Evaluation of algorithms performance for SH WFS
• WFS noise
• Impact of Sodium profile
• LGS aberrations
• Alternative WFS
• Pyramid (smaller detectors)
• Dynamic refocus (by segmented mirrors on
  sub-pupils?)

0.75 "/pixel
Poster by Matteo Lombini
1.0 "/pixel
1.5 "/pixel
Non linearity
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Focus reconstruction scheme
F(?)
F(?5) Na
F(?6) Na
F(?1) Na
F(?4) Na
F(?2) Na
F(?3) 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

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NGS Wavefront Sensor
NGS measured in IR benefit from high-order loop
correctionBaseline H band
T 5 ms
Target WFE 100 nm (3 NGS)? 4 mas residual
jitter per NGS
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)
4-5 mas/pixel, 1"?1" FoV ? at least 256?256
pixels detector required. This is 2? the
foreseen high speed IR sensor by Teledyne
(128?128, 5e- RON _at_900Hz, J. Beletic, SPIE 2008
Marseille)
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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

WFS1
WFS2
WFS3
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Error sources
Estimated by Fourier code cone effect
degradation factor
Input to NGS WFS design and sky coverage
estimation
Top level allocations
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
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Strehl Ratio
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Encircled Energy (0.8" seeing)
500 mas
200 mas
75 mas
50 mas
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Performance Sky coverage
Nominal average performance over MICADO field of
view (53"?53")
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
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PSF modeling for scientific analysis
Simulated PSF
PSF model
Strehl Ratio ? 0.6 Image size 2.7"
?
Model components
Airy
Hexagonal Moffat
Moffat
Moffat
DIFFRACTION
FITTING ERRORS, UNSEEN MODES
SEEING
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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 INFRA-2007-2.2.1.28