LGS spot truncation mitigation in ELTs: optimizing the pixel usage L.Blanco 1 , C. Correia 1 , T. Fusco 2 , B. Neichel 1 , Y. Ono 1 1 Laboratoire d’Astrophysique de Marseille (UMR7326 - CNRS-INSU, Université d’Aix-Marseille) 2 ONERA - The French Aerospace Lab
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LGS spot truncation mitigation in ELTs: optimizing …research.iac.es/congreso/AO4ELT5/media/thursday/ao4elt5...LLT Detector plane Pupil plane 25” 1” On a ~40m telescope Full E-ELT
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LGS spot truncation mitigation in ELTs: optimizing the pixel usage
L.Blanco1, C. Correia1, T. Fusco2, B. Neichel1, Y. Ono1
1 Laboratoire d’Astrophysique de Marseille (UMR7326 - CNRS-INSU, Université d’Aix-Marseille) 2 ONERA - The French Aerospace Lab
LGS Spot elongation
LLT
Sodium layer
D e t e c t o r plane
T ~ 20km
H ~ 90km
Distance from launch site
P u p i l plane
Predicted spot elongation pattern
LLT
2AO4ELT 2017
3
LLT
D e t e c t o r plane
P u p i l plane
25”
1”
Ideally, we need subapertures with 25x25 pixels of ~1”
For 80x80 subapertures, we need 2000 x 2000 pixels
Most likely, we will have no more than 10x10 pixels
On a ~40m telescope
LGS Spot elongation
Strong truncation
AO4ELT 2017
4
• À la Diolaiti/Schreiber, we simulate elongated spots (normalized by the Na profile intensity)
• Compute the centroid of each sub-aperture, and project the resulting wave-front on Zernikes
• No elongation: no aberration
• No truncation: Tip/Tilt/Focus only
Impact of truncation on a single WFSAl
titu
de
Time
AO4ELT 2017
5
(blue = peak; error bar = rms ; histogram = avg ; red = cumulative of avg)
Impact of truncation on a single WFSAl
titu
de
Time
• Select 11 Na profiles showing a large variety of configurations
• For each profile, and each time, compute the residual aberrations (for a single WFS)
6 LGS-Asterism diameter : 42’’ 30% central obscuration
High flux
Performance increases as we discard subapertures with too large an elongation/truncation
WFE due to elongation reduced from 152nm to 106nm RMS
Elongated spots cropping
223nm
270nm247nm
AO4ELT 2017 22
152nm106nm
Differential subaperture weighting
- à la Tallon 2008/Robert 2010 - Takes into account the elongation in the noise covariance matrix - Takes into account cross-coupling between X and Y slopes
AO4ELT 2017 23
Differential subaperture weighting
- Tallon 2008/Robert 2010 - Takes into account the elongation in the noise covariance matrix - Takes into account cross-coupling between X and Y slopes
AO4ELT 2017 24
Differential subaperture weighting
- Tallon 2008/Robert 2010 - Takes into account the elongation in the noise covariance matrix - Takes into account cross-coupling between X and Y slopes
AO4ELT 2017 25
Differential subaperture weighting
- Tallon 2008/Robert 2010 - Takes into account the elongation in the noise covariance matrix - Takes into account cross-coupling between X and Y slopes
6 LGS-Asterism diameter : 42’’ 30% central obscuration
High flux
Very perturbed profile with sharp peak at high altitude Unstable loop when taking into account all subapertures Weighting mandatory for full pupil High cropping (40%) improves performance over weighting but far from ideal
6 LGS-Asterism diameter : 42’’ 30% central obscuration
High flux
Stre
hl in
K-b
and
(%)
Very perturbed profile with sharp peak at high altitude Unstable loop when taking into account all subapertures Weighting mandatory for full pupil High cropping (40%) improves performance over weighting but far from ideal
AO4ELT 2017 35
Truth sensor
How many modes do we need to measure to remain below a prescribed WFE due to spot elongation ?
AO4ELT 2017 36
Truth sensor
How many modes do we need to measure to remain below a prescribed WFE due to spot elongation ?
AO4ELT 2017 37
8x8 truth sensor sufficient to remain below 10nm at all times
Truth sensor
How many modes do we need to measure to remain below a prescribed WFE due to spot elongation ?
AO4ELT 2017 38
Single Top hat Double Very
narrowMulti peak
Very wide
Top hat +peak
10nm z1 z10 z14 z14 z28 z42 z56
20nm z1 z1 z1 z1 z1 z42 z42
30nm z1 z1 z1 z1 z1 z42 z42
40nm z1 z1 z1 z1 z1 z28 z28
50nm z1 z1 z1 z1 z1 z28 z28
223nm
270nm247nm
WFS sensorWithout truncation
160 pixels10pix/subap
160 pixels10 pix/subap
160 pixels12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
Corner Shack-Hartmann
AO4ELT 2017 39
223nm
270nm247nm
WFS sensorWithout truncation
160 pixels10pix/subap
160 pixels10 pix/subap
160 pixels12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
Corner Shack-Hartmann
Not needed
AO4ELT 2017 40
223nm
270nm247nm
WFS sensorWithout truncation
160 pixels10pix/subap
160 pixels10 pix/subap
160 pixels12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WFS sensorWithout truncation
160 pixels10pix/subap
160 pixels10 pix/subap
160 pixels12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
Corner Shack-Hartmann
AO4ELT 2017 41
Corner Shack-Hartmann
WFS
sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional S
H
Corner S
H
Pupil cropping increases
AO4ELT 2017 42
WFS sensorWithout truncation
160 pixels10pix/subap
160 pixels10 pix/subap
160 pixels12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WFS sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WF
S s
ensor
Without
truncation
160 p
ixels
10pix
/subap
160 p
ixels
10 p
ix/s
ubap
160 p
ixels
12 p
ix/s
ubap
Conventional S
H
Corn
er
SH
Pupil
cro
ppin
g incre
ases
WFS sensorWithout truncation
160 pixels10pix/subap
160 pixels10 pix/subap
160 pixels12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WFS sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WF
S s
ensor
Without tr
uncation
160 p
ixels
10pix
/subap
160 p
ixels
10 p
ix/s
ubap
160 p
ixels
12 p
ix/s
ubap
Conventional S
H
Corn
er
SH
Pupil
cro
ppin
g incre
ases
WFS
sen
sor
With
out t
runc
atio
n
160
pixe
ls
10pi
x/su
bap
160
pixe
ls
10 p
ix/s
ubap
160
pixe
ls
12 p
ix/s
ubap
Con
vent
iona
l SH
Cor
ner S
H
Pup
il cr
oppi
ng in
crea
ses
WFS sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WF
S s
ensor
With
out tru
ncatio
n
160 p
ixels
10pix
/subap
160 p
ixels
10 p
ix/s
ubap
160 p
ixels
12 p
ix/s
ubap
Conventio
nal S
H
Corn
er S
H
Pupil c
roppin
g in
cre
ases
6 LGS configuration
4 LGS configuration
Corner Shack-Hartmann
WFS
sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional S
H
Corner S
H
Pupil cropping increases
AO4ELT 2017 43
WFS sensorWithout truncation
160 pixels10pix/subap
160 pixels10 pix/subap
160 pixels12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WFS sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WF
S s
ensor
Without
truncation
160 p
ixels
10pix
/subap
160 p
ixels
10 p
ix/s
ubap
160 p
ixels
12 p
ix/s
ubap
Conventional S
H
Corn
er
SH
Pupil
cro
ppin
g incre
ases
WFS sensorWithout truncation
160 pixels10pix/subap
160 pixels10 pix/subap
160 pixels12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WFS sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WF
S s
ensor
Without tr
uncation
160 p
ixels
10pix
/subap
160 p
ixels
10 p
ix/s
ubap
160 p
ixels
12 p
ix/s
ubap
Conventional S
H
Corn
er
SH
Pupil
cro
ppin
g incre
ases
WFS
sen
sor
With
out t
runc
atio
n
160
pixe
ls
10pi
x/su
bap
160
pixe
ls
10 p
ix/s
ubap
160
pixe
ls
12 p
ix/s
ubap
Con
vent
iona
l SH
Cor
ner S
H
Pup
il cr
oppi
ng in
crea
ses
WFS sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WF
S s
ensor
With
out tru
ncatio
n
160 p
ixels
10pix
/subap
160 p
ixels
10 p
ix/s
ubap
160 p
ixels
12 p
ix/s
ubap
Conventio
nal S
H
Corn
er S
H
Pupil c
roppin
g in
cre
ases
6 LGS configuration
4 LGS configuration
Corner Shack-Hartmann
WFS
sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional S
H
Corner S
H
Pupil cropping increases
AO4ELT 2017 44
WFS sensorWithout truncation
160 pixels10pix/subap
160 pixels10 pix/subap
160 pixels12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WFS sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WF
S s
ensor
Without
truncation
160 p
ixels
10pix
/subap
160 p
ixels
10 p
ix/s
ubap
160 p
ixels
12 p
ix/s
ubap
Conventional S
H
Corn
er
SH
Pupil
cro
ppin
g incre
ases
WFS sensorWithout truncation
160 pixels10pix/subap
160 pixels10 pix/subap
160 pixels12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WFS sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WF
S s
ensor
Without tr
uncation
160 p
ixels
10pix
/subap
160 p
ixels
10 p
ix/s
ubap
160 p
ixels
12 p
ix/s
ubap
Conventional S
H
Corn
er
SH
Pupil
cro
ppin
g incre
ases
WFS
sen
sor
With
out t
runc
atio
n
160
pixe
ls
10pi
x/su
bap
160
pixe
ls
10 p
ix/s
ubap
160
pixe
ls
12 p
ix/s
ubap
Con
vent
iona
l SH
Cor
ner S
H
Pup
il cr
oppi
ng in
crea
ses
WFS sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WF
S s
ensor
With
out tru
ncatio
n
160 p
ixels
10pix
/subap
160 p
ixels
10 p
ix/s
ubap
160 p
ixels
12 p
ix/s
ubap
Conventio
nal S
H
Corn
er S
H
Pupil c
roppin
g in
cre
ases
6 LGS configuration
4 LGS configuration
Corner Shack-Hartmann
WFS
sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional S
H
Corner S
H
Pupil cropping increases
AO4ELT 2017 45
WFS sensorWithout truncation
160 pixels10pix/subap
160 pixels10 pix/subap
160 pixels12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WFS sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WF
S s
ensor
Without
truncation
160 p
ixels
10pix
/subap
160 p
ixels
10 p
ix/s
ubap
160 p
ixels
12 p
ix/s
ubap
Conventional S
H
Corn
er
SH
Pupil
cro
ppin
g incre
ases
WFS sensorWithout truncation
160 pixels10pix/subap
160 pixels10 pix/subap
160 pixels12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WFS sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WF
S s
ensor
Without tr
uncation
160 p
ixels
10pix
/subap
160 p
ixels
10 p
ix/s
ubap
160 p
ixels
12 p
ix/s
ubap
Conventional S
H
Corn
er
SH
Pupil
cro
ppin
g incre
ases
WFS
sen
sor
With
out t
runc
atio
n
160
pixe
ls
10pi
x/su
bap
160
pixe
ls
10 p
ix/s
ubap
160
pixe
ls
12 p
ix/s
ubap
Con
vent
iona
l SH
Cor
ner S
H
Pup
il cr
oppi
ng in
crea
ses
WFS sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WF
S s
ensor
With
out tru
ncatio
n
160 p
ixels
10pix
/subap
160 p
ixels
10 p
ix/s
ubap
160 p
ixels
12 p
ix/s
ubap
Conventio
nal S
H
Corn
er S
H
Pupil c
roppin
g in
cre
ases
6 LGS configuration
4 LGS configuration
Corner Shack-Hartmann
WFS
sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional S
H
Corner S
H
Pupil cropping increases
AO4ELT 2017 46
WFS sensorWithout truncation
160 pixels10pix/subap
160 pixels10 pix/subap
160 pixels12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WFS sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WF
S s
ensor
Without
truncation
160 p
ixels
10pix
/subap
160 p
ixels
10 p
ix/s
ubap
160 p
ixels
12 p
ix/s
ubap
Conventional S
H
Corn
er
SH
Pupil
cro
ppin
g incre
ases
WFS sensorWithout truncation
160 pixels10pix/subap
160 pixels10 pix/subap
160 pixels12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WFS sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WF
S s
ensor
Without tr
uncation
160 p
ixels
10pix
/subap
160 p
ixels
10 p
ix/s
ubap
160 p
ixels
12 p
ix/s
ubap
Conventional S
H
Corn
er
SH
Pupil
cro
ppin
g incre
ases
WFS
sen
sor
With
out t
runc
atio
n
160
pixe
ls
10pi
x/su
bap
160
pixe
ls
10 p
ix/s
ubap
160
pixe
ls
12 p
ix/s
ubap
Con
vent
iona
l SH
Cor
ner S
H
Pup
il cr
oppi
ng in
crea
ses
WFS sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WF
S s
ensor
With
out tru
ncatio
n
160 p
ixels
10pix
/subap
160 p
ixels
10 p
ix/s
ubap
160 p
ixels
12 p
ix/s
ubap
Conventio
nal S
H
Corn
er S
H
Pupil c
roppin
g in
cre
ases
6 LGS configuration
4 LGS configuration
Corner Shack-Hartmann
WFS
sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional S
H
Corner S
H
Pupil cropping increases
AO4ELT 2017 47
WFS sensorWithout truncation
160 pixels10pix/subap
160 pixels10 pix/subap
160 pixels12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WFS sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WF
S s
ensor
Without
truncation
160 p
ixels
10pix
/subap
160 p
ixels
10 p
ix/s
ubap
160 p
ixels
12 p
ix/s
ubap
Conventional S
H
Corn
er
SH
Pupil
cro
ppin
g incre
ases
WFS sensorWithout truncation
160 pixels10pix/subap
160 pixels10 pix/subap
160 pixels12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WFS sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WF
S s
ensor
Without tr
uncation
160 p
ixels
10pix
/subap
160 p
ixels
10 p
ix/s
ubap
160 p
ixels
12 p
ix/s
ubap
Conventional S
H
Corn
er
SH
Pupil
cro
ppin
g incre
ases
WFS
sen
sor
With
out t
runc
atio
n
160
pixe
ls
10pi
x/su
bap
160
pixe
ls
10 p
ix/s
ubap
160
pixe
ls
12 p
ix/s
ubap
Con
vent
iona
l SH
Cor
ner S
H
Pup
il cr
oppi
ng in
crea
ses
WFS sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WF
S s
ensor
With
out tru
ncatio
n
160 p
ixels
10pix
/subap
160 p
ixels
10 p
ix/s
ubap
160 p
ixels
12 p
ix/s
ubap
Conventio
nal S
H
Corn
er S
H
Pupil c
roppin
g in
cre
ases
6 LGS configuration
4 LGS configuration
Corner Shack-Hartmann
WFS
sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional S
H
Corner S
H
Pupil cropping increases
AO4ELT 2017 48
WFS sensorWithout truncation
160 pixels10pix/subap
160 pixels10 pix/subap
160 pixels12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WFS sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WF
S s
ensor
Without
truncation
160 p
ixels
10pix
/subap
160 p
ixels
10 p
ix/s
ubap
160 p
ixels
12 p
ix/s
ubap
Conventional S
H
Corn
er
SH
Pupil
cro
ppin
g incre
ases
WFS sensorWithout truncation
160 pixels10pix/subap
160 pixels10 pix/subap
160 pixels12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WFS sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WF
S s
ensor
Without tr
uncation
160 p
ixels
10pix
/subap
160 p
ixels
10 p
ix/s
ubap
160 p
ixels
12 p
ix/s
ubap
Conventional S
H
Corn
er
SH
Pupil
cro
ppin
g incre
ases
WFS
sen
sor
With
out t
runc
atio
n
160
pixe
ls
10pi
x/su
bap
160
pixe
ls
10 p
ix/s
ubap
160
pixe
ls
12 p
ix/s
ubap
Con
vent
iona
l SH
Cor
ner S
H
Pup
il cr
oppi
ng in
crea
ses
WFS sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WF
S s
ensor
With
out tru
ncatio
n
160 p
ixels
10pix
/subap
160 p
ixels
10 p
ix/s
ubap
160 p
ixels
12 p
ix/s
ubap
Conventio
nal S
H
Corn
er S
H
Pupil c
roppin
g in
cre
ases
6 LGS configuration
4 LGS configuration
Corner Shack-Hartmann
WFS
sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional S
H
Corner S
H
Pupil cropping increases
AO4ELT 2017 49
WFS sensorWithout truncation
160 pixels10pix/subap
160 pixels10 pix/subap
160 pixels12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WFS sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WF
S s
ensor
Without
truncation
160 p
ixels
10pix
/subap
160 p
ixels
10 p
ix/s
ubap
160 p
ixels
12 p
ix/s
ubap
Conventional S
H
Corn
er
SH
Pupil
cro
ppin
g incre
ases
WFS sensorWithout truncation
160 pixels10pix/subap
160 pixels10 pix/subap
160 pixels12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WFS sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WF
S s
ensor
Without tr
uncation
160 p
ixels
10pix
/subap
160 p
ixels
10 p
ix/s
ubap
160 p
ixels
12 p
ix/s
ubap
Conventional S
H
Corn
er
SH
Pupil
cro
ppin
g incre
ases
WFS
sen
sor
With
out t
runc
atio
n
160
pixe
ls
10pi
x/su
bap
160
pixe
ls
10 p
ix/s
ubap
160
pixe
ls
12 p
ix/s
ubap
Con
vent
iona
l SH
Cor
ner S
H
Pup
il cr
oppi
ng in
crea
ses
WFS sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WF
S s
ensor
With
out tru
ncatio
n
160 p
ixels
10pix
/subap
160 p
ixels
10 p
ix/s
ubap
160 p
ixels
12 p
ix/s
ubap
Conventio
nal S
H
Corn
er S
H
Pupil c
roppin
g in
cre
ases
6 LGS configuration
4 LGS configuration
Corner Shack-Hartmann
WFS
sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional S
H
Corner S
H
Pupil cropping increases
AO4ELT 2017 50
WFS sensorWithout truncation
160 pixels10pix/subap
160 pixels10 pix/subap
160 pixels12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WFS sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WF
S s
ensor
Without
truncation
160 p
ixels
10pix
/subap
160 p
ixels
10 p
ix/s
ubap
160 p
ixels
12 p
ix/s
ubap
Conventional S
H
Corn
er
SH
Pupil
cro
ppin
g incre
ases
WFS sensorWithout truncation
160 pixels10pix/subap
160 pixels10 pix/subap
160 pixels12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WFS sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WF
S s
ensor
Without tr
uncation
160 p
ixels
10pix
/subap
160 p
ixels
10 p
ix/s
ubap
160 p
ixels
12 p
ix/s
ubap
Conventional S
H
Corn
er
SH
Pupil
cro
ppin
g incre
ases
WFS
sen
sor
With
out t
runc
atio
n
160
pixe
ls
10pi
x/su
bap
160
pixe
ls
10 p
ix/s
ubap
160
pixe
ls
12 p
ix/s
ubap
Con
vent
iona
l SH
Cor
ner S
H
Pup
il cr
oppi
ng in
crea
ses
WFS sensor
Without truncation
160 pixels
10pix/subap
160 pixels
10 pix/subap
160 pixels
12 pix/subap
Conventional SH
Corner SH
Pupil cropping increases
WF
S s
ensor
With
out tru
ncatio
n
160 p
ixels
10pix
/subap
160 p
ixels
10 p
ix/s
ubap
160 p
ixels
12 p
ix/s
ubap
Conventio
nal S
H
Corn
er S
H
Pupil c
roppin
g in
cre
ases
6 LGS configuration
4 LGS configuration
Corner SH always better than conventional SH for a given # of subapertures
51
->Completely discarding 10-40% of the truncated subapertures actually increases Strehl Ratio (depending on Sodium profiles)
->Combining subaperture differential weighting and cropping allow us to reach quasi-ideal performance on most sodium profiles
-> Help release constraints on Truth Sensor design: 8(x8) is enough !
-> Corner Shack-Hartmann to optimize pixel usage
AO4ELT 2017
Conclusion
AO4ELT 2017 52
- Thorough analysis of more parameters (truncation, d/r0, central obscuration, asterism diameter, #LGS…)
- Advanced centroiding algorithms/strategies
- Actual ELT M4 geometry (see N. Schwartz talk tomorrow 12:30)
- Temporal aspects, sodium profil evolution during the night
On-going work
The authors thanks the European Research Council for its support through the grant ERC-STG-2015 ICARUS 678777