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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Dealing with turbulence in MCAO
Roberto Ragazzoni, Yazan Almomany, Carmelo Arcidiacono, Renato Falomo, Jacopo Farinato, Marco Gullieuszik, Osservatorio Astronomico di Padova (Italy);
Emiliano Diolaiti, Matteo Lombini, Osservatorio Astronomico di Bologna (Italy);Alessia Moretti, Osservatorio Astronomico di Padova (Italy);
Giampaolo Piotto, Univ. degli Studi di Padova (Italy);Enrico Marchetti, Robert Donaldson, European Southern Observatory (Germany);
Roberto Turolla, Univ. Degli Studi di Padova (Italy)
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
What is MCAO…??? Why is important the knowledge of the 3D turbulence???
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Telescope
DM1 DM2
Turbulent layers#2 #1
Atmosfera
WFS
UP
Multi Conjugated Adaptive Optics: MCAO
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
An historical perspective…
• MCAO is a “vision” of J. Beckers in 1988
• Pyramid WFS envisaged in 1995
• Layer Oriented approach is shown in Backaskog 1999 and Munich 2000
• LO approved as part of MAD in 2001
• MCAO with 3SH and LO
are on the sky in 2007!
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Canary, fall 2001
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Why pyramid..?
• They take advantage of the full aperture (spot is diffraction limited on the pin of the pyramid) Better limiting magnitude
• Better aliasing (larger Strehl in HO mode)
• It is a pupil plane WFSensor!
• It is “cheap” in terms of pixels usage
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Prototyping(4 stars)
Opticaldesign
Optomechanicaldesign
Glass andAlluminum
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
0,00
10,00
20,00
30,00
40,00
50,00
60,00
70,00
7 8 9 10 11 12 13 14 15 16 17
V Magnitude
Str
ehl R
atio
(%
)
400 Hz - 0.85"
200 Hz - 0.85"
100 Hz - 0.85"
50 Hz - 0.85"
400 Hz - 0.45"
200 Hz - 0.45"
100 Hz - 0.45"
50 Hz - 0.45"
Laboratory test in closed loop give evidence of higher limiting magnitude for the Layer Oriented WFS w.r.t the Star Oriented ~1.5 magnitude fainter
LOWFS SHWFS
vWFS on MAD vs 3SH…: FoV of single stars enlarger ~0.95arcsec!
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
The MAD-LO run• Basically the whole group of LO-MAD plus
ESO support (3 initially, then 1)
• Total of 9 contiguous nights
• First 3 night of technical run under ESO responsibility
• Then 6 nights of “GTO” basically devoted to science
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
70.5”
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
• 107x107arcsec
• GLAO
• 5 NGSs
• Vmag tot=13.8
• Here is S=10%
• Var. +/- 3%
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Not a star!!!
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
A. Moretti et al.
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
• We think to have material for further 3 science papers on other objects…
• A very productive run indeed, but….
• Which is the achieved quality compared to the SO one?
• Which is the sky coverage one can compute given the actual performances?
• Any answer will be plagues by doubts about seeing, f_G, scaling laws…
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
A. Moretti et al.
Omega Cen (public data)NGC6388 (LO data)
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
LayerOriented
Star Oriented
Layer oriented
Star Oriented
With an uniform “standard” reduction magnitude errors are slightly (10%) betterfor LO than SO, and viceversa for centroiding
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
0.45”
0.60”
0.95”
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
3x V=11.5
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
3x V=12
3x V=13
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
3x V=12
3x V=13
~1.5mag
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Red: estimates given in the 2002 paperBlue: left – actual measurements in the sky; right – laboratory measures
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Red: estimates given in the 2002 paperBlue: left – actual measurements in the sky; right – laboratory measures
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Remember that the CCD is blue-sensitive…!!!
0.70 … 0.99 0.10 … 0.25 0.07 … 0.25
!
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Areas to make MCAO with NGSs more sensitive…
• Using the Taylor hypothesys
• Layer Oriented “sees” the layers of turbulence so can use “several” previous measurements to estimate the coming one (not prediction, but better SNR of WFS…
“Frozen” layer2000
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Areas to make MCAO with NGSs more sensitive…
• Using non linear co-addition of stars
• It is well known that enlarging the FoV do not improve the correction because it is lowered the thickness of turbulence sampled… if linearly coadded!!!
a
2001
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Linear or non-linear…???
Layer you are “looking” (say 8km)
a few stars
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Linear or non-linear…???
Layer you are “looking” (say 8km)
a lot of stars
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Linear or non-linear…???
Layer you are “looking” (say 8km)
a few stars
This layer is sampled Ok…
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Linear or non-linear…???
Layer you are “looking” (say 8km)
a lot of stars
This layer is smoothed out!!
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Linear or non-linear…???
Layer you are “looking” (say 8km)
a lot of stars
+ + +
Numerically averaging leads to the same trouble!
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Linear or non-linear…???
Layer you are “looking” (say 8km)
a lot of stars
multiply or adding the square
It only goes to zero if all the WF is flatted…
Page 45
Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Linear or non-linear…???
Layer you are “looking” (say 8km)
a lot of stars
multiply or adding the square
It only goes to zero if all the WF is flatted…
Page 46
Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Linear or non-linear…???
Layer you are “looking” (say 8km)
a lot of stars
multiply or adding the square
It only goes to zero if all the WF is flatted…
Page 47
Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Linear or non-linear…???
Layer you are “looking” (say 8km)
a lot of stars
multiply or adding the square
It only goes to zero if all the WF is flatted…
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Propagation noise is more complex…
1st DM
2nd DM
Pupil plane
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Non-linear behaviour…• Algorithm is not conventional as the “sign” of
correction is unknown• A toy-model using the “bang-bang” algorithm
gives a bandwidth that is at worst 2x less…• There is a geometrical limit, that is about 10’ for
a 42m telescope (and 25’ for a 100m one…)• This makes the gain in FoV of 25• So the overall gain is in the ballpark of 12..!!!!• One order of magnitude improvement in sky
coverage!!!
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Future of Layer Oriented• A LO instrument started in 2002 now would
produce big science• NIRVANA is not optimized for deep single arm
MCAO but, ok…• In the timescale of a new instrument LGSs
should prove their maturity (or not???)
• Unexplored ways to improve sensitivity include Taylor hypothesis usage and non-linear coaddition of reference stars
• Mixing up LGS and NGS is a safe, robust way, and there are unexplored new schemes for that
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Metapupil
4 NGSs…and 2 LGSs!
Pupil planePupil plane Focal plane
NGS
LGS
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Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Conclusions…
• Beating 3D turbulence, after 20yrs from the J”D”B is a reality…
• MCAO is in its infancy…
• There are unexplored realms where NGSs based MCAO can achieve larger sky coverage…
• LGS are being deployed on a few sites and will progress as well…
• Stay tuned for a turbulent future!!!