Thierry Fusco Gérard Rousset NAOS-CONICA (a.k.a NACO) for the VLT
Jan 06, 2016
Thierry FuscoGérard Rousset
NAOS-CONICA (a.k.a NACO) for the VLT
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NACO History
~5 years
CFT for the VLT Coude AO feasibility study: Feb. 91CONICA contract signed with MPIA et al: 1991VLT Coude AO feasibility study: Matra-Marconi-Space in 92-93VLT Coude AO project (4 AO systems) cancelled: Council Dec 93NAOS concept is proposed by ESO to STC-FC-Council: end 1994CONICA is redesigned by MPIA et al.: end 1994NAOS Preliminary Inquiry & CFT: Dec. 94- March 96NAOS audit: March 96- December 96NAOS contract signed with ONERA et al.: March 97CONICA FDR: mid 98NAOS PDR - FDR: Oct. 98 - June 99NAOS-CONICA PAE: Sept. 2001NAOS-CONICA first light: Nov. 2001NACO open to the community: Oct 2002
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NAOS in figures
4 Institutes : ONERA, LAOG, ODP, ESO
5-year project ~5 Meuros 60 FTEs Tests in France in 2001 First light 25/11/2001
NAOS: 2.3 tons
CONICA: 0.9 tons
(attached to Nasmyth rotator)
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Two Shack-Hartmann Wavefront Sensors,each including 2 pupil samplings: 14x14 (144 valid subap.) and 7x7 (36)
NAOS main features (1/2)…
IR WFS :• Spectral range: 0.8 - 2.5 mm• 14x14 array + 2 arrays of 7x7 on 3 fixed detector areas (0.8 and 0.4 arcsec/pix)• Rockwell Hawaii 1024x1024 pixels frame rate from 180 to 15 Hz noise : from 10 to 20 e- • 36 configurations !!!
VWFS : • Spectral range: 0.45 - 1 mm • 2 interchangeable lenslet arrays (0.29 and 0.58 arcsec/pixel)• EEV CCD 128x128 pixels, 16 outputs (ESO) frame rate from 444 to 15 Hz binning, windowing noise : 2.9e- to 5.4e-• 48 configurations!!!
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NAOS main features (2/2)
Dichroic Wheel:• 2 neutral and 3 dichroic BS
WFS Field Selector: • NGS in 2 arcmin FOV• Tracking (refraction, flexures, moving object)
Deformable mirror (Cilas)• 185 actuators (piezo-stacked), 10 m stroke
2-axis Tip/Tilt Mirror: 2.1 mas resolution
Real time Computer (Shakti):• 0dB Error BW: 27 Hz (V) and 22 Hz (IR)• modal optimization (every 2 mn)• on-line performance and seeing
Off-line preparation software
Observation software: • NAOS configuration, control of Field Selector• Aberration pre-compensation, chopping
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Diameter: 2m Max Length: 3m Thickness: 0.7m
IR WFS
V-WFS
DM Output
input
Mechanical structure PM 2
PM 1
TTM
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Pupil sampling
185 useful actuators
144 useful subapertures
Telescope pupil
Central obscuration
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CONICA
1-5 microns (1Kx1K) 34 filters 4 grisms 7 cameras 3 slits Polarimetry Coronography Fabry-Perot Imaging
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Flange to “rotate” CONICA
Imaging: 1-5 µmPolarisationCoronographySpectro 1-5 µm: max 2500Fabry Perot: R=1800
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VLT Nasmyth Platform
NAOS
CONICA
VLT-UT4: F/15Cable twist
… and NAOS-CONICA became NACO …
They lived happy everafter … and they had plenty of photons …
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• High order correction in near IR (Sr(K)=70%)• Faint limiting magnitude star in V (Mv>17)• IR wavefront sensing for embedded objects• Compatibility with LGS operation• Minimization of instrument thermal and sky bkg effects
• Minimise the number of optical surfacesno derotator direct rotation of NACO
• AO with Chopping and Counter chopping• Very low flexure requirements (NAOS & CONICA)• “background limiter” to reduce dichroic background
• High image quality for CONICA (Sr(K)>90%)• Low Instrumental background <1e• One detector for 1-5 m!• Many CONICA observing modes: Imaging, coronagraphy, Low resolution spectroscopy, FP, polarimetry
And now … let’s go on sky … with a pit-stop in lab
NACO challenges
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12Result: SR 65 % @ 0.93 arcsec seeing (specification 70 %)
First laboratory results Turbulent image AO corrected image Image without
turbulence
SR = 69% 90%Seeing 0.6 arcsec
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Paranal re-integration NOOOOOOOO !Oh my god …
I have to make it work ! YESSSSSSSS !
I’m gonna observe in J, H, K, L, M …
I’m gonna detect exoplanets
The astronomer The instrumentalist
(use to be an astronomer )
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Let’s go on the telescope
Is this going to work??
Well … maybe ...
Of course it will !!!!!!!!!!
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High Strehl (K)50%
And yes … it worked and it is still working
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Faint star correctionStrehl (K)=17%
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The Galactic Centre with and without AO in L'-band seen by NAOS(Clénet et al. 2004)
The Galactic CentreThe Galactic Centre
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Thetis
Differential tracking
Composite image H-K20.6 arcsec diameterresolution 70 mas or 410 km~10 sec exposure time
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Io with NAOS-CONICALong wavelengths
capabilitiesBr-L’
230/4.2 s exposure68mas or 210 km
1.2 arcsec diameter
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On-sky SR behavior versus magnitude
Visible WFS IR WFS
• Bright NGS : SR loss of 20-30 %• Faint NGS : significant correction
Stars: seeing 0.7 ’ ’, crosses: 1.1 ’ ’, diamonds: 1.1 ’ ’ ; 14x14 arrays: large symbols, 7x7 arrays: small symbols
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Exoplanet detection with NACO
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SR loss sources (1/2)Vibrations detected on WFS data:
On-sky
Laboratory
No vibration Vibration lines
• 16 - 18 Hz : 3000 -10000 nm²• 48 - 55 Hz : 2000 - 5000 nm²• 68 - 70 Hz : 500 - 1000 nm²
No vibration on Comas
Variations in amplitude and
occurence
No vibration in laboratoryNothing on internal source: telescope vibrations
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SR loss sources (2/2)
Telescope vibrations:
Strehl loss estimated to 10 %
Main influence on Tip-Tilt modes but other excitations detected on high order modes
Vibrations not compensated for: out of the NAOS temporal bandwidth
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Differential aberrations in CONICA and dichroics
Without turbulence, SR ~ 93 % in K with pre-compensation
With
pre-com
pen
sation b
y NA
OS
d
eformab
le mirror
No
com
pen
sati
on
At 2.15 m
At 1.09 m
SR = 93 %SR = 89 %
SR= 56% SR =66%
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Conclusion
In median seeing conditions: SR ~ 50% at K band; best Sr(K)=64% on sky
Substantial compensation with very faint NGS: Mv=17.6, SR=6% (gain of 7)
Fully automated operation (VLT software) Many features available in NAOS for specific astronomical
observations: IR WFS differential refraction, pointing model tracking on moving object, chopping, counter-chopping
241 scientific papers so far
=> 34.5 papers per year => Good scientific return !