Scuola Nazionale di tecnologie astromiche
Napoli, 23-28 Settembre 2002
Sistemi Adattivi per l’astronomia:
concetti ed esempi
S. Esposito, Osservatorio Astrofisico di Arcetri, INAF
Sommario
 Immagini da telescopi a terra e turbolenza atmosferica
 Concetti e parametri fondamentali dei
sistemi ottici adattivi Astronomici
 I sistemi adattivi di:
 CFHT/Gemini
 VLT
 TNG
 Novità nel settore: Sistema adattivo di LBT
 La prossima tappa: Extremely Large Telescopes
AO system layout
Atmosfera turbolenta
Keck Telescope
Keck Telescope
Immagini da telescopi a terra
Measured
Intensity


  
I ()   O() P(  )d

I( )
Teoretical Point Spread function
Obj. Intensity
distribution

O()

P ( )
l/D
1.22 l/D
La Modulation transfer function (MTF)
~  ~  ~ 
Optical Transfer function
I (f )  O(f )  P (f )
 
 
~
MTF= P(f )   W ( r  d )W ( r ) dr
La MTF teorica
MTFs
Overlap area
f  d/l
D
W = Funzione Pupilla
1 r < D/2
0 r > D/2
r0/l
D/l
Turbolenza I
Strati turbolenti


6
dn  79 P / T 10 dT
2
~20Km
~1mm/K/m
telescopio
Funzione di struttura della fase

 2
53
D (r )  ( r2 )  ( r1 )  6.88r r0 
Media statistica delle
differenze quadratiche
di fase fra due punti
Valori di r0 a 0.5
e 2.2 mm
Acromaticità della perturbazione in mm
r0  l
65
I polinomi di Zernike
i/j
2
3
4
5
6
7
8
9
10
2
0.449
0
0
0
0
0
0.0142
0
0
3
0
0.449
0
0
0
0.0142
0
0
0
4
5
6
7
8
0
0
0
0
0.0142
0
0
0
0.0142
0
0.0232
0
0
0
0
0
0.0232
0
0
0
0
0
0.0232
0
0
0
0
0
0.00619
0
0
0
0
0
0.00619
0
0
0
0
0
0
0
0
0
0
Matrice di varianza-covarianza statistica
9
0
0
0
0
0
0
0
0.00619
0
10
0
0
0
0
0
0
0
0
0.00619
Turbolenza II
MTF media in atmosfera
Turbolenta
MTFs
W = Funzione Pupilla

i (r )
r  D/2
e
0
r  D/2
Area di coerenza
D = r0
r0/l
D/l
Effetto della correzione adattiva !
MTF ( f )  T0 ( f )  exp  0.5D (lf ) 
Questioni fondamentali
 Numero di gradi di libertà ?
Natt ~ (D/r0)^2
 Tempi caratteristici di
funzionamento ?
Nsamp ~ (D/r0)^2
 Numero di punti di sampling del wf ?
 Massima sep. Oggetto scientifico
stella di guida ?
Angolo Isoplanatico

Angolo di decorrelazione:
Angolo isoplanatico 
 ~ r0 / h
r0
h
Evoluzione temporale
0 ~ r0 / v
l 
2
5
  10 m sec
2
  25 sec

v
telescopio
D
 >> D/V
1
Stelle di riferimento laser
Tilt Indetermination
Pos. reale
Pos. apparente
Focus Anisoplanatism
  r 1 h / H 
NGS
LGS
LGS
Strato di
sodio
10 km
90 km
Strato turbolento
d
r
Tel. pupil
Tel. pupil
h
Loop di controllo
Natt ~ (D/r0)^2
Control
system
C

R
[Natt x Nsens]
S
Nsens ~ 2 (D/r0)^2
Bibliografia
•"Adaptive Optics for Astronomy”,
Francois Roddier (ed.), Cambridge University Press, 1999
•"Adaptive Optics for Astronomical Telescopes",
John W. Hardy, Oxford Books, 1998
•"Adaptive Optics for Astronomy",
ed. Danielle M. Alloin & Jean-Marie Mariotti, Kluwer Academic Publishers, Dordrecht, 1994
•"Imaging Through Turbulence",
Michael C. Roggemann & Byron Welsh, CRC Press, 1996
•"Principles of Adaptive Optics",
Robert K. Tyson, Academic Press, 1997
•"Adaptive Optics for Atmospheric Compensation",
James E. Pearson (ed.), SPIE Milestone Series, Volume MS 92
•“Introduction to Wavefront Sensors” (Tutorial Texts in Optical Engineering, Vol Tt18,)
Joseph M. Geary, Society of Photo-optical Instrumentation Engineers, 1995
•Babcock, H. W. "Adaptive Optics Revisited." Science 249, 253-257, 1990.
•Beckers, J. M. "Adaptive Optics for Astronomy: Principles, Performance, and Applications." Ann.
Rev. Astron. Astrophys. 31, 13-62, 1993.
•Hubin, N. and Noethe, L. "Active Optics, Adaptive Optics, and Laser Guide Stars." Science 262,
1390-1394, 1993.
•Collins, G. P. "Making Stars to See Stars--DOD Adaptive Optics Work is Declassified." Physics
Today 45, 17-21, Feb. 1992.
Pueo & Hokupaa: Curvature AO
Wavefront Sensor
Deformable Mirror
Sampling Rate
Imager
Curvature 36 elements,
2 arcsec WFS FOV,
12 arcsec guide star patrol radius
36 element Bimorph
60mm pupil
DM stroke sufficient for ~ 0.9arcsec seeing
1 kHz
University of Hawaii's QUIRC
1-2.5 micron HgCdTe 1k2 HAWAII array,
19.7 milliarcsec/pixel
~20 arcsec FOV
Def mirrors: bimorph
Geometria
degli elettrodi
Deformazione del bimorfo
V proporzionale al laplaciano della sup. ottica
No. Di attuatori
13-85
DM size
30-200 mm
Geometria attuatori
radiale
Voltaggio
100 V
Freq. Di risonanza
500 Hz
Curvature sensor: concept



I1 r   I 2 (r )
f  f  l 2
 w fr / l 

 
I1 r   I 2 (r )
l
Esiste un valore minimo per l !
I / I  f2/l
 f 

l  l
 d sub 
2
Curvature sensor: optics
Pupil image
Oscillating membrane
Pupil image
2l
NAOS images
NAOS images
Thetis
Differential tracking
Composite image H-K
20.6 arcsec diameter
resolution 70 mas or 410 km
~10 sec exposure time
Naos@VLT
VLT Adapter
NAOS
Cable Twist
CONICA
NAOS at Paranal Nov. 2001
Naos optical layout
CONICA
Input focus
Deformable
mirror
Input
parabola
VLT Nasmyth focus
Dichroic
Tip-Til
mirror
Output
parabola
WFS input
focus
Naos def. Mirror: 185 attuatori
Piezo-Stacked monolithic
deformable mirrors
V proporzionale allo spostamento della sup. ottica
No. Di attuatori
30 – 349
Spaziatura attuatori
5-10 mm
DM size
50-150 mm
Geometria attuatori
griglia quadrata
Voltaggio
100 V
Freq. di risonanza
500-1000 Hz
Shack-Hartmann sensor: concept
2sub
x
S


x 
 w(r ) xdr
subap
I1  I 2  I 3  I 4
 x  sub S x  sub
I1  I 2  I 3  I 4
1
Asub
Shack-Hartmann sensor: optics
NAOS WFS characteristic
Visible WFS
Infrafred WFS
Wavelenght range
0.45-1.0 mm
0.8-2.5 mm
14x14 FOV
Mag. range
2.3 arcsec
0-13
5.15 arcsec
0-11
7x7 FOV
Mag. range
4.6 arcsec
13-19
5.15
11-15
Deetector
128x128 EEV
CCD50
1024x1024
Rockwell hawaii
NAOS IR WFS
TNG
Primo anello di diffrazione
Settembre 2001
NICS@K band, FWHM 0.15
Marzo 2002
NICS ,K band,
35% SR
TNG optical layout
Speckle Module
Tip-Tilt module
HO module PS, SHS
F/32 dal telescopio
Pyramid WFS: concept
Immagini
pupille

I2

I1

Y
I3
R mod

I4
Sx(x,y) = ([I1(x,y)+I4(x,y)] - [I2(x,y)+I3(x,y)])/Itot
y0
x0
Sy(x,y) = ([I1(x,y)+I2(x,y)] – [I3(x,y)+I4(x,y)])/Itot
X
w/x = R/F Sx
Pyramid WFS: optics
Un raffronto........
 f 
l
 w
S lmin  l d 
 sub 
f  f  l
2
2
l
w / x 
Sx
d sub
PS
CS
SH
w / x  Open
subSloop
x
w/x = R/F Sx
w/x
Ad oggi……………….
• Curvature systems: modesto numero di gardi di libertà (dof)
– Canada France Hawaii Telescope: 13 dof, 14th mag
– Univ. of Hawaii: 19 dof, 12th mag
– San Pedro Martir (Baja CA): 19 dof
– Subaru: 19 dof
– Hokupaa on Gemini Telescope: 36 dof, 13-17th mag
– Hokupaa 85 (under construction): 85 dof
• Shack-Hartmann systems: tendono ad avere più gradi di liberta ma
richiedono stelle di rif. più brillanti.
– Lick: 61 dof, 13.5 mag
– Palomar: 241 dof
– Keck: 250 dof, 13.5 mag
– ADONIS: 50 dof (?), 13 mag
– VLT (ESO) NAOS
• Pyramid Sensor
- TNG: 97dof, mag ?
Scuola Nazionale di tecnologie astromiche
Napoli, 23-28 Settembre 2002
Sistemi Adattivi per l’astronomia:
concetti ed esempi II
S. Esposito, Osservatorio Astrofisico di Arcetri, INAF
Sommario
 Immagini da telescopi a terra e turbolenza atmosferica
 Concetti e parametri fondamentali dei
sistemi ottici adattivi Astronomici
 I sistemi adattivi di:
 CFHT/Gemini
 VLT
 TNG
 Novità nel settore: Sistema adattivo di LBT
 La prossima tappa: Extremely Large Telescopes
System Overview & Location
LUCIFER window LGS
LUCIFER
NGS
AGW
System Key features
Adaptive Secondary mirror: LBT672
[4839-85], A. Riccardi
Improves AO channel transmission ~ 40% (WFS)
Actuators pitch ~ 28cm ~ ro @ 0.75 mm, (0.8” seeing V Band)
effective correction down to sensing wavelenght
Pyramid wavefront Sensor (PS)
Better performance WRT Shack-Hartmann > 1 mag
Pupil sampling adjustable using on-chip binning, LBT
30x30,15x15,10x10...
Moveable WFS
Allows use of small refractive optics, 32mm Ø max.
Reference star acquisition on a 3x2 arcmin FOV
Small AOS opto-mechanics 320x400 mm (20 kg)
Reduces costs, flexures, turbulence.....
WFS Opto -Mechanical design
Two WFS optical path:
Pyramid sensor optical path: blue, 500mm, [0.6-0.9 mm]
Tech./Acquisition camera: red
F/15 LBT beam reflected
on LUCIFER 15° window
(1) Fixed telecentric lens, 80mm ø
2 arcmin FOV, (3x2 arcmin)
(2) Refocusing triplet, 32mm ø
320mm
(5) Fast steering mirror: ± 0.8” (PI)
(6) Pupil Rotator
(8) Refractive pyramid, 2.5” FOV ø
(9) Camera triplet, 10mm ø
(10) Pyramid sensor CCD
(12) Technical/acquisition camera
max FOV 30 arcsec
Four on-board motorized
parts (3),(4),(6),(9)
ADC (4)
400mm
Secondario adattivo: Concetto
Secondario
adattivo
Secondario
convenzionale
•Minori superfici
calde
WFS
TTM
Coll.
BS
DM
•K band: riduzione
tempo esposizione
di 2-2.6 volte
•Attuatori elettromagnetici: ampio
stroke (LBT>100mm)
Sci. Camera Correttore di TT e Sci. Camera
wind buffeting
WFS
Secondario adattivo per LBT
Ogni AdSec:
672 attuatori
911mm diam.
2x8.4m specchi primari
Da MMT336 a LBT672
LBT: Gregoriano
672 attuatori
MMT: Cassegrain
336 attuatori
642mm
911mm
Schema di LBT676
Esapodo
Flangia di interfaccia e
supporto strutturale
3 scatole di elettr.
raffreddate
Esapodo fisso
Cold-plate e
supporto per att.
Leve astatiche
Ref-plate di Zerodur
(spessore 50mm)
Shell deformabile
di Zerodur (spessore 1.6mm)
Attuatori e sensori capacitivi
Armature sens. Capacit. (ref.plate)
(MMT336) shell asferica
642mm diam.
2mm spessore
Magneti
(12mm diam.)
Elettronica per LBT672
All’AO
Fibra comunicazione diagnostica
supervisor
400Mbit/s
Gigabit Ethernet Switch
Connessione in dasy chain
Comunicaz.
Real-time
2.9 Gbit/s
Communication Board
(1x backplane)
Communication Board
(1x backplane)
Reference Signal
Generator Board (1x backplane)
Communication Board
(1x backplane)
Reference Signal
Generator Board (1x backplane)
Reference Signal
Generator Board (1x backplane)
DSP control Board (14x backplane)
DSP control Board (14x backplane)
DSP control Board (14x backplane)
± 48V, 35 A
Alimentazione
DSP control Board (14x backplane)
DSP control Board (14x backplane)
Potenza di calcolo totale:
60 Gmac/s (32bit fp)
Ricostruttore real-time a bordo
WFS: 30x30 => 34-47ms (z-m)
Trasferimento slopes: 20ms
Communication Board
(1x backplane)
Reference Signal
Generator Board (1x backplane)
DSP control Board (14x backplane)
Communication Board
(1x backplane)
Communication Board
(1x backplane)
Reference Signal
Generator Board (1x backplane)
Reference Signal
Generator Board (1x backplane)
DSP control Board (14x backplane)
DSP control Board (14x backplane)
Liquid cooled crates,
each comprehending 2 backplanes (3x)
Distribution boards
Actuators
Coil
Specchio sottile
Gap
Segnale di riferimento
3 scatole di elettronica raffreddate
2 crate per scatola
84 schede DSP custom
4 DSP/scheda - 8 attuatori/scheda
32-bit floating-point 180Mmac/s
(MMT: 16-bit integer 40Mmac/s)
Prestazioni
r0=15cm@500nm
Diametro
N attuatori
Fitting error
Efficienza att.
Potenza nell’att.
Potenza nei crate
Comun. Real-time
Comun. Diagnost.
DSP
MMT
641 mm
336
72 nm
0.5 N/W1/2
0.41 W/act
4.7 W/act
160 Mbit/s
No dedicated
40 Mmac/s (int)
LBT
911 mm
672
64 nm
0.5 N/W1/2
0.19 W/act
3.8 W/act
2.9 Gbit/s
400 Mbit/s
160 Mmac/s
System performance simulations I
Parameter
Simulation values
Atmospheric parameters
Two layers with wind velocity 15 m/s
Fried parameter 15cm @500nm => 0.67 arcsec
Turbulence outer scale 40m
Guide Star
Spectral type K5,
V-magnitude in range 9.85—17.5
LBT Telescope
Diameter 8.25m
Obstruction ratio 0.11
Pyramid WFS
WF sampling: 10x10, 15x15, 30x30 (obtained using on chip binning)
Exposure time: in range 1 – 10ms
RON from 3.5 to 8.4 e- according to frame rate (SciMeasure camera specs)
Tilt mod.: ±1 ±2 (30x30sub), ±3 (15x15sub), ±4,±5,±6 (10x10sub) l/D
System Transmission
0.9^3 * 0.7 * CCD QE = 0.4, (CCD average QE = 0.8 @ [600—900 nm])
Wavefront reconstructor:
LBT672 mirror modes
Time filtering
36, 44, 55 and 66 modes @ 10x10 conf.
78, 105 and 136 modes @ 15x15 conf.
231, 351 and 496 modes @ 30x30 conf
Pure integrator with gain = 0.5
Sistem performance simulations II
15x15
30x30
Max SRs: 87,93,96
10x10
SR 0.2, mR = 14.3, 15.5, 16.7
On-Axis SR 20 %
Max off-axis 30 arcsec
Sky Coverage
(b=20,l=180)
J band H band
K band
Pyramid (PS)
11
33
83
Shack-Hartmann
6
18
47
SR 0.2, mR = 15.5 (SH), 16.7(PS)
Current situation & schedule
SciMeasure Analytical
Systems, Inc.
DR
RS232
4X HIGH SPEED COMMUNICATION MODULES
ETHERNET COMMUNICATION
TIMING REFERENCE RX
TIMING REFERENCE TX
CCD60 FASTI controller design and test LLLCCD
WFS HO
Final controller test BI L3CCD
Test tower
AO system parts acquisition: Oct/Nov 2002
ETHERNET
CONTROLLER
.
Co
mm
AO system HW cost: 600K USD (two units)
Manpower: 10 person / year (two years)
People involved: ~ 8-10 people
is s
Shipping
Installation
2001
2002
2003
2004
J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J
act design
LBT672
Adaptive Secondary
procurement
P36' test P45 test Closed loop
inst&test CL WFS
Design phase
assemb. P45+WFS+RTR
Tower +LBT672
Wavefront sensor
MMTtest
OptoMecc Procur. and test
inst.
RT software
System Software
Debugging
Diagnostic Design phase 1 Design phase 2
Coding phase 1
Coding phase 2
SERDES
P45+PWFS+RTR lab test: 4Q 2002 -1Q 2003
BOTTOM HEAT SINK
BACKPLANE SLOT CONNECTORS
LBT672+PWFS tower test: 4Q 2003 -1Q 2004
ELT’s
Tecnologia dei secondari
adattivi per ELTs
ELT’s
Euro 50
Optical diagram for MCAO
Turb. Layers
#1
Atmosphere
UP
#2
Telescope
WFS
DM1
DM2