dealing with turbulence in mcao roberto ragazzoni inaf – padova (italy) alghero, sept. 17 th 2008...
TRANSCRIPT
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)
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???
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
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!
Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Canary, fall 2001
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
Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Prototyping(4 stars)
Opticaldesign
Optomechanicaldesign
Glass andAlluminum
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!
Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
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
Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
70.5”
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%
Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Not a star!!!
Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
A. Moretti et al.
Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
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…
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)
Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
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
Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
0.45”
0.60”
0.95”
Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
3x V=11.5
Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
3x V=12
3x V=13
Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
3x V=12
3x V=13
~1.5mag
Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
Dealing with turbulence in MCAO Roberto RagazzoniINAF – Padova (Italy)
Alghero, Sept. 17th 2008Astronomy meets Metereology
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
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
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
!
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
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
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
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
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…
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!!
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!
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…
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…
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…
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…
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
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!!!
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
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
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!!!