Adaptive Optics: Concepts & Key Numbers Jean-Marc Conan
ONERA - Optics Dept (France)
[email protected]
Adaptive Optics: Concepts & Key Numbers
FAWSA – JM Conan – Nov. 2016
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Adaptive Optics Principle
Correcting for turbulence with adaptive optics
Key components & System specification
Closing the loop & Corrected Images
New Developments in Adaptive Optics
eXtreme Adaptive Optics: the search for exoplanets
Wide Field Adaptive Optics : origin of the universe
From VLT (10 m class) to ELT (30 m class) telescopes
Beyond astronomical applications ?
Astronomical Imaging Through Turbulence •
Astronomy often implies high angular resolution imaging of distant objects: solar system bodies, stars, galaxies…
FAWSA – JM Conan – Nov. 2016
Loss in resolution and sensitivity
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D/r0 key parameter gives resolution ratio seeing over diffraction
FAWSA – JM Conan – Nov. 2016
λ/D
D = 10m
λ/D = 10 mas λ/D = 45 mas 1 mas = 10-3 arcsec
In IR, large telescopes (10m for instance) give same resolution as amateur 60cm instrument 5
400 Years of Ground Based Astronomical Instrumentation •
From few centimeters in 1609…
…to 39 meters… in 2024 (?)
D=39 m Isaac Newton D=0.15 m 1671
Galileo Galilei
FAWSA – JM Conan – Nov. 2016
1953 Concept Optique Adaptative par Babcock
2024 ?
1990 Optique Adaptative COME-ON @ 3.6m ESO
Angular Resolution 4 ” [arcsec]
1”
1”
1”
1” 0.100”
λ/D diffraction limited case
0.040” VLTs
0.010” ELTs
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Adaptive Optics Principle
Incoming Plane Wave
Object
Atmospheric turbulence Turbulent wavefront Deformable Mirror
Uncorrected Image
Reconstruction & Control
WaveFront Sensor
FAWSA – JM Conan – Nov. 2016
Corrected wavefront
Corrected Image
Imaging Camera
¾ Adaptive Optics allows to reach near diffraction limited angular resolution ¾ Main components: Turbulence ; Def. Mirror ; Wave-Front Sensor ; Rec. & Control 7
Adaptive Optics: Concepts & Key Numbers
Correcting for turbulence with adaptive optics
Key components & System specification
Closing the loop & Corrected Images
New Developments in Adaptive Optics
eXtreme Adaptive Optics: the search for exoplanets
Wide Field Adaptive Optics : origin of the universe
From VLT (10 m class) to ELT (30 m class) telescopes
Beyond astronomical applications ?
FAWSA – JM Conan – Nov. 2016
Adaptive Optics Principle
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AO Performance: Main Contributors to Residual Phase Residual phase variance
σ2 φ residual = Incoming Plane Wave
σ2fitting 䊽 spatial sampling
Atmospheric turbulence
(Deformable Mirror pitch) Turbulent wavefront Deformable Mirror
+ σ2wfs-noise 䊽 number of photons (guide star magnitude)
Reconstruction & Control
+ σ2tempo 䊽 temporal sampling WaveFront Sensor
FAWSA – JM Conan – Nov. 2016
Corrected wavefront
'ŽŽĚŝŵĂŐŝŶŐƋƵĂůŝƚLJƌĞƋƵŝƌĞƐ͗ Imaging Camera
㼼ϯ
σ φ residual << λim
Is it a perfect plane wave?
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FAWSA – JM Conan – Nov. 2016
PSD alias Energy versus spatial frequency
Residual Phase after AO Correction Turbulent Phase PSD Kolmogorov Spectrum α f -11/3
Rejection by AO
Corrected Phase
σ2wfs-noise & σ2tempo
Low Frequencies partially corrected by AO
σ2fitting High Frequencies non corrected by AO
Spatial Frequencies (1/m)
fc = 1/(2 pitch)
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IR Adaptive Optics: Key numbers
Incoming Plane Wave
Object
Atmospheric turbulence
Turbulent Phase Amplitude PV 10 à 50 µm
Turbulent wavefront Deformable Mirror
Uncorrected Image
Reconstruction & Control
WaveFront Sensor
FAWSA – JM Conan – Nov. 2016
Corrected wavefront
Corrected Image
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Imaging Camera
Objective: Residual Amplitude PV < 1 µm (fraction of λim)
Implies a precise wave-front sensing precision : °spatial resolution ~ 50 cm ~ r 0 @ λim °temporal resolution ~ 2 ms ∝ (r0 @ λim / Vwind) °« bright » guide star > 100 photons / m ² / ms (0~12)
What if VIS AO ? r0 ÷ 6 !
Deformable Mirrors (DMs): Small Post-Focal DMs
Thin optical plate with aluminum coating Piezo-electric / Magnetic / Electrostatic actuators often on Cartesian grid Distance between actuators = pitch Typical size of DM: few cms to few decimeters implies optical conjugation between DM & Tel. pupil
FAWSA – JM Conan – Nov. 2016
pitch
Piezo DM (CILAS Orléan) Magnetic DM (ALPAO Grenoble)
pitch = spatial resolution ~ 50 cm ~ r0 @ λim 12
Deformable Mirrors (DMs): Adaptive Secondary Mirrors
Thin optical plate (1-2 m) Magnetic actuators (voice coil + magnets) driven by Nact control signals (generally current) Distance between actuators = pitch
MMT Deformable Secondary
FAWSA – JM Conan – Nov. 2016
typical diameter 1 or 2 meters ! Included in the telescope itself
Shack-Hartmann Wave-Front Sensor (WFS) d: sub-aperture size
FAWSA – JM Conan – Nov. 2016
WFS data are called “slopes”
« bright » guide star > 100 photons / m² / ms (0~12) 14
Typical design for VLT class IR Adaptive Optics : NAOS since 2001 on ESO VLT @ Paranal (Chile)
Beta Pictoris
FAWSA – JM Conan – Nov. 2016
NAOS (coupled to CONICA IR Camera)
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15x15 actuators
500 Hz sampling frequency (alias 2 ms temporal resolution)
Guide star magnitude for good performance 0 12
Faint companion: brown dwarf
Adaptive Optics: Concepts & Key Numbers
Correcting for turbulence with adaptive optics
Key components & System specification
Closing the loop & Corrected Images
New Developments in Adaptive Optics
eXtreme Adaptive Optics: the search for exoplanets
Wide Field Adaptive Optics : origin of the universe
From VLT (10 m class) to ELT (30 m class) telescopes
Beyond astronomical applications ?
FAWSA – JM Conan – Nov. 2016
Adaptive Optics Principle
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We can now close the loop ! ONERA AO bench Analyseur de surface d’onde (Shack-Hartmann)
miroir déformable SAM
caméra d’imagerie
FAWSA – JM Conan – Nov. 2016
RTC: PC-Linux (Shaktiware)
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FAWSA – JM Conan – Nov. 2016
Observation of Io (Jupiter satellite) with AO@Keck
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Adaptive Optics: Concepts & Key Numbers
FAWSA – JM Conan – Nov. 2016
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Adaptive Optics Principle
Correcting for turbulence with adaptive optics
Key components & System specification
Closing the loop & Corrected Images
New Developments in Adaptive Optics
eXtreme Adaptive Optics: the search for exoplanets
Wide Field Adaptive Optics : origin of the universe
From VLT (10 m class) to ELT (30 m class) telescopes
Beyond astronomical applications ?
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FAWSA – JM Conan – Nov. 2016
108 light-years
1010 light-years eWXGHGHVJDOD[LHVSULPRUGLDOHV Ö QDLVVDQFHGHO·XQLYHUV *SF
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Adaptive Optics: Concepts & Key Numbers
FAWSA – JM Conan – Nov. 2016
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Adaptive Optics Principle
Correcting for turbulence with adaptive optics
Key components & System specification
Closing the loop & Corrected Images
New Developments in Adaptive Optics
eXtreme Adaptive Optics: the search for exoplanets
Wide Field Adaptive Optics : origin of the universe
From VLT (10 m class) to ELT (30 m class) telescopes
Beyond astronomical applications ?
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eXtreme Adaptive Optics: SPHERE since 2014 on ESO-VLT
Objective :
FAWSA – JM Conan – Nov. 2016
detection of exo-planets around nearby stars
flux ratio between star / exo-planet ~ 1 million !
SPHERE system :
XAO system : 41x41 actuators ; sampling frequency 1200 Hz ; wave-front sensing on star 0 10
+ Coronagraph to suppress star photons
+ spectro-imaging instruments
+ smart post-processing
Hence direct detection & analysis of exo-planet photons
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SPHERE … from concept to reality Premières idées 2002 Design final 2008
Intégration à Grenoble (2011-13)
FAWSA – JM Conan – Nov. 2016
Sur VLT 2014
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SPHERE compared with american competitor GEMINI-GPI GPI
*3
20 minutes in H band
15 minutes in H2 band
HD 165054, G4V, V=8.5 28
Preliminary reduced data © A. Vigan (LAM)
Adaptive Optics: Concepts & Key Numbers
Correcting for turbulence with adaptive optics
Key components & System specification
Closing the loop & Corrected Images
New Developments in Adaptive Optics
eXtreme Adaptive Optics: the search for exoplanets
Wide Field Adaptive Optics : origin of the universe
From VLT (10 m class) to ELT (30 m class) telescopes
Beyond astronomical applications ?
FAWSA – JM Conan – Nov. 2016
Adaptive Optics Principle
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FAWSA – JM Conan – Nov. 2016
Anisoplanatism issue
BAD NEWS : Guide star has to be bright and close to object of interest (within few arcsec) !
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FAWSA – JM Conan – Nov. 2016
FAWSA – JM Conan – Nov. 2016
2 arcmin
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10 arcsec
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FAWSA – JM Conan – Nov. 2016
Laser Guide Star for Adaptive Optics
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Lasers for each and every telescope Gemini Sud
Sodium : λ = 589 nm Continuous Laser ~20 W
Subaru
(Keck)
WHT
FAWSA – JM Conan – Nov. 2016
VLT ESO
laser guide stars delivering the required few 100 ph/m²/ ms & low order aberrations (tip-tilt, focus...) measurement on very faint natural guide stars ~ 1 photon / m² / ms 38
Rayleigh : λ = 532 nm Pulsed @ 10kHz ~ 20 W
Multiplication of the Laser Guide Stars
FAWSA – JM Conan – Nov. 2016
There must be a smarter way...
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Tomographic AO : think collective !
FAWSA – JM Conan – Nov. 2016
This should do!
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5 Sodium Laser Guide Stars
+ Tomographic AO GEMS
GEMINI South Chile 8m telescope
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+ GSAOI IR Camera
5 Etoiles Laser
x3
+ 3 Etoiles Naturelles très faibles
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Crédit Benoit Neichel AO4ELT3
Adaptive Optics: Concepts & Key Numbers
Correcting for turbulence with adaptive optics
Key components & System specification
Closing the loop & Corrected Images
New Developments in Adaptive Optics
eXtreme Adaptive Optics: the search for exoplanets
Wide Field Adaptive Optics : origin of the universe
From VLT (10 m class) to ELT (30 m class) telescopes
Beyond astronomical applications ?
FAWSA – JM Conan – Nov. 2016
Adaptive Optics Principle
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Extremely Large Telescopes are BIG ! European ELT 39 m telescope 798 individual segments (1.45m) to be cophased Up to 6 Laser Guide Stars 2.5 m deformable mirror with ~ 5316 actuators (2 mm thick, 6 petals)
fusion of ~30000 wave-front sensing data for tomographic AO !
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FAWSA – JM Conan – Nov. 2016
Pupils through the ages
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Adaptive Optics: Concepts & Key Numbers
FAWSA – JM Conan – Nov. 2016
53
Adaptive Optics Principle
Correcting for turbulence with adaptive optics
Key components & System specification
Closing the loop & Corrected Images
New Developments in Adaptive Optics
eXtreme Adaptive Optics: the search for exoplanets
Wide Field Adaptive Optics : origin of the universe
From VLT (10 m class) to ELT (30 m class) telescopes
Beyond astronomical applications ?
High Resolution Imaging @ Onera Optics Dpt (DOTA) more than 100 researchers @ DOTA ; ~15 on High Resolution Imaging
Earth-Space Observations (astronomy, earth obs...) Propagation through turbulence, adaptive optics, active optics
Earth-Space Optical Links Turbulence effects on high data rate links and clock transfer
Ophtalmology Aberrometry, adaptive optics assisted retinal imaging and surgery
FAWSA – JM Conan – Nov. 2016
Microscopy Optical wave control for 2-photon microscopy and 3D imaging
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Beam shaping for high power lasers
more than 10 docs and post-docs on these research activities
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