Minisymposia Abstracts

Speaker: Brent Ellerbroek
TMT project Office
Title: Progress in Atmospheric Tomography Methods for Extremely Large Telescopes over the Past Decade
Abstract: TBA

Speaker: Andreas Neubauer
Johannes Kepler University
Title: Cumulative wavefront reconstructor for the Shack-Hartmann sensor
Abstract: TBA

Speaker: Simone Esposito
Osservatorio Astrofisico di Arcetri
Title: Wavefront Reconstruction for the AO system FLAO of Large Binocular Telescope (LBT)
Abstract: TBA

Speaker: Clementine Bechet
ESO, Munich
Title: Algorithms for fast wavefront reconstruction and model update : needs for next generation Adaptive Optics
Abstract: The astrophysical objectives of the future Extremely Large Telescopes (ELTs) will be achieved only with innovative Adaptive Optics (AO) systems to compensate the wavefront distortions induced by the turbulence in the atmosphere above the telescope. The challenge is to cope with a huge jump in size and complexity of the future AO systems, such that the wavefront correct ion requires to be done faster, better and in a smarter way than in the existing systems.
The Fractal Iterative Method (FriM) has been developed to provide a fast algorithm for Minimum-Variance reconstruction and control on ELTs. The principle of the algorithm based on the "inverse approach" is presented, as well as its performance results on European Southern Observatory end-to-end AO simulator. We show successful tests of single conjugate AO, and ground-layer AO, as well as first results of AO with tomography (MCAO). In that way, we emphasize remark able benefits of our approach with respect to complexity, closed-loop configuration, noise correlation in wavefront sensing, and tomography quality.
In a second part, we extend the inverse approach to investigate the update of non-stationary model parameters involved in FriM, or any other AO control. The problem of system parameters identification in closed-loop AO is investigated here, which is critical for next generation AO. We introduce a novel iterative method in that purpose. First simulations results enhance the ability to retrieve internal model parameters directly from data, without introducing additional disturbance.

Speaker: Ronny Ramlau
Johannes Kepler University
Title: Iterative Reconstructors for Multi Conjugate Adaptive Optics
Abstract: TBA

Speaker: Curtis Vogel
The Optical Science Company
Title: Modeling and parameter estimation for deformable mirrors used in ground-based astronomical adaptive optics
Abstract: TBA

Speaker: Francois-Xavier Dupe
Laboratoire de Cosmologie et Statistiques
Title: Recovering the galaxy density
Abstract: TBA

Speaker: Adrienne Leonard
Pisa
Title: Compressed Sensing for Weak Lensing
Abstract: Weak gravitational lensing allows us to map the distribution of matter in the universe by measuring the small distortions to galaxy images arising due to the gravitational potential along the line of sight. The measured shear is effectively a convolution of the matter overdensity with a broad radial kernel encoding geometrical information. Therefore, the weak lensing problem can be modeled as an instance of compressed sensing, as we know that the matter overdensity is mostly sparse in some wavelets domains. In this case, the sensing operator models an integration along each line of sight, from low redshift (i.e. close distance) to high redshift (i.e. far away distance). Then, we exploit current results on the compress sensing theory in order to build an efficient method for estimating the matter density along lines of sight using most of the theoretical knowledge available. More precisely, the reconstruction problem is cast as a constraints convex optimization problem, where we seek a sparse solution under data fidelity constraints. We also characterize the solution and prove the convergence of the global scheme. The results show that we are able to reconstruct the matter cluster in different redshifts without the smooth and shift issues that occur in the current state-of-art methods.


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