Transcript Document

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
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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
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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
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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
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Thermal emission
Requirement on thermal emission < 50% (telescope + sky) @ K
No cooling for T < 30C
No cooling for T < 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/paranal/temperature/)
AO for ELT – Paris, 22-26 June 2009
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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
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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

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?)
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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
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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
256256 pixels detector required.
This is 2 the foreseen high speed IR
sensor by Teledyne (128128, 5e- RON
@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
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
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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
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Strehl Ratio
NGS search field
AO for ELT – Paris, 22-26 June 2009
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Encircled Energy (0.8" seeing)
500 mas
200 mas
75 mas
50 mas
AO for ELT – Paris, 22-26 June 2009
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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
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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
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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 INFRA2007-2.2.1.28
AO for ELT – Paris, 22-26 June 2009
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