Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Dealing with turbulence in MCAO
Document related concepts
no text concepts found
Transcript
Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 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 Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 What is MCAO…??? Why is important the knowledge of the 3D turbulence??? Roberto Ragazzoni INAF – Padova (Italy) Dealing with turbulence in MCAO Alghero, Sept. Turbulent layers #2 Astronomy meets Metereology 17th 2008 Telescope #1 Atmosfera UP Multi Conjugated Adaptive Optics: MCAO WFS DM1 DM2 Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 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 Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 Canary, fall 2001 Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 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 Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 Optomechanical design Prototyping (4 stars) Optical design Glass and Alluminum Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Astronomy meets Metereology Alghero, Sept. 17th 2008 vWFS on MAD vs 3SH…: FoV of single stars enlarger ~0.95arcsec! 70,00 400 Hz - 0.85" 200 Hz - 0.85" 60,00 LOWFS 100 Hz - 0.85" 50 Hz - 0.85" SHWFS 50,00 400 Hz - 0.45" 200 Hz - 0.45" Strehl Ratio (%) 100 Hz - 0.45" 50 Hz - 0.45" 40,00 30,00 20,00 10,00 0,00 7 8 9 10 11 12 13 14 15 16 V Magnitude 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 17 Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 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 Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. 70.5” Astronomy meets Metereology 17th 2008 Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. • • • • • • 107x107arcsec GLAO 5 NGSs Vmag tot=13.8 Here is S=10% Var. +/- 3% Astronomy meets Metereology 17th 2008 Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 Not a star!!! Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 A. Moretti et al. Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 • 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… Roberto Ragazzoni INAF – Padova (Italy) Dealing with turbulence in MCAO Alghero, Sept. Astronomy meets Metereology 17th 2008 A. Moretti et al. NGC6388 (LO data) Omega Cen (public data) Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 LayerOriented Star Oriented Layer oriented Star Oriented With an uniform “standard” reduction magnitude errors are slightly (10%) better for LO than SO, and viceversa for centroiding Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. 0.45” 0.60” 0.95” Astronomy meets Metereology 17th 2008 Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. 3x V=11.5 Astronomy meets Metereology 17th 2008 Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 3x V=12 3x V=13 Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 3x V=12 3x V=13 ~1.5mag Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 Red: estimates given in the 2002 paper Blue: left – actual measurements in the sky; right – laboratory measures Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 Red: estimates given in the 2002 paper Blue: left – actual measurements in the sky; right – laboratory measures Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. 0.70 … 0.99 Astronomy meets Metereology 17th 0.10 … 0.25 2008 0.07 … 0.25 ! Remember that the CCD is blue-sensitive…!!! Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 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… 2000 “Frozen” layer Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 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 Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 Linear or non-linear…??? a few stars Layer you are “looking” (say 8km) Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 Linear or non-linear…??? a lot of stars Layer you are “looking” (say 8km) Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 Linear or non-linear…??? a few stars This layer is sampled Ok… Layer you are “looking” (say 8km) Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 Linear or non-linear…??? a lot of stars This layer is smoothed out!! Layer you are “looking” (say 8km) Roberto Ragazzoni INAF – Padova (Italy) Dealing with turbulence in MCAO Alghero, Sept. Astronomy meets Metereology 17th 2008 Linear or non-linear…??? a lot of stars Layer you are “looking” (say 8km) Numerically averaging leads to the same trouble! + + + Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 Linear or non-linear…??? a lot of stars Layer you are “looking” (say 8km) It only goes to zero if all the WF is flatted… multiply or adding the square Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 Linear or non-linear…??? a lot of stars Layer you are “looking” (say 8km) It only goes to zero if all the WF is flatted… multiply or adding the square Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 Linear or non-linear…??? a lot of stars Layer you are “looking” (say 8km) It only goes to zero if all the WF is flatted… multiply or adding the square Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 Linear or non-linear…??? a lot of stars Layer you are “looking” (say 8km) It only goes to zero if all the WF is flatted… multiply or adding the square Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 Propagation noise is more complex… 1st DM 2nd DM Pupil plane Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 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 Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 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 Ragazzoni INAF – Padova (Italy) Alghero, Sept. Pupil plane Astronomy meets Metereology 17th Focal plane 2008 Pupil plane LGS NGS Metapupil …and 2 LGSs! 4 NGSs Dealing with turbulence in MCAO Roberto Ragazzoni INAF – Padova (Italy) Alghero, Sept. Astronomy meets Metereology 17th 2008 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!!!
