The Experts below are selected from a list of 24360 Experts worldwide ranked by ideXlab platform
Andrea Masiero - One of the best experts on this subject based on the ideXlab platform.
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ECC - Efficient algorithms for the reconstruction and prediction of atmospheric turbulence in AO systems
2014 European Control Conference (ECC), 2014Co-Authors: Alessandro Beghi, Angelo Cenedese, Andrea MasieroAbstract:Technological advances and the ever-growing human quest for improving the resolution of telescope observations are motivating the design of larger and larger Ground Telescopes: indeed, the larger is the telescope lens diameter, the better is the diffraction limited resolution of the telescope. Unfortunately, the terrestrial atmospheric turbulence, if not properly compensated, negatively affects the telescope observations, limiting its real resolution. Adaptive Optics (AO) systems are used in large Ground Telescopes in order to compensate the effect of the atmosphere, and hence to make the real telescope resolution be determined by the diffraction properties of the lens. AO systems exploit the measurements of wavefront sensors to estimate the current values of the atmospheric turbulence, and compensate its effect by properly adapting the shape of a set of deformable mirrors. As the size of the telescope lenses is increasing, then the size of the AO system (e.g. the number of deformable mirror actuators and the size of the wavefront sensor) is increasing as well. This causes the increase of the computational burden needed to compute a proper compensation of the effect of the atmosphere. Consequently, as the potential telescope resolution increases, the task of the AO systems becomes more challenging. Motivated by the need of providing AO solutions useful for the next generations of Ground Telescopes, then a number of efficient algorithms have been recently considered in the literature to solve the problems related to the AO system. This paper considers the combination of a recently proposed very efficient phase reconstruction method, namely the CuRe, with a properly defined Kalman filter in order to obtain a dynamic compensation of the atmospheric turbulence. The performance of the proposed approach is investigated in some simulations.
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Multiscale phase screen synthesis based on local principal component analysis.
Applied optics, 2013Co-Authors: Alessandro Beghi, Angelo Cenedese, Andrea MasieroAbstract:Motivated by the increasing importance of adaptive optics (AO) systems for improving the real resolution of large Ground Telescopes, and by the need of testing the AO system performance in realistic working conditions, in this paper we address the problem of simulating the turbulence effect on Ground telescope observations at high resolution. The procedure presented here generalizes the multiscale stochastic approach introduced in our earlier paper [Appl. Opt.50, 4124 (2011)], with respect to the previous solution, a relevant computational time reduction is obtained by exploiting a local spatial principal component analysis (PCA) representation of the turbulence. Furthermore, the turbulence at low resolution is modeled as a moving average (MA) process, while previously [Appl. Opt.50, 4124 (2011)] the wind velocity was restricted to be directed along one of the two spatial axes, the use of such MA model allows the turbulence to evolve indifferently in all the directions. In our simulations, the proposed procedure reproduces the theoretical statistical characteristics of the turbulent phase with good accuracy.
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CDC - Turbulence modeling and Kalman prediction for the control of large AO systems
52nd IEEE Conference on Decision and Control, 2013Co-Authors: Alessandro Beghi, Angelo Cenedese, Andrea MasieroAbstract:Measurements of large Ground Telescopes are affected by the presence of the terrestrial atmospheric turbulence: local changes of the atmospheric refraction index (e.g. due to wind and temperature variations) cause a non flat surface of the wavefront of light beams incoming on the telescope, thus degrading the quality of the observed images. Adaptive Optics (AO) systems are of fundamental importance to reduce such atmospheric influence on Ground Telescopes and thus to obtain high resolution observations. The goal of the AO system is that of estimating and compensating the atmospheric turbulence effect by properly commanding a set of deformable mirrors. Because of delays in the closed loop system, the Kalman filter plays an important role in ensuring an effective control performance by providing good atmosphere predictions. However, the need of periodically updating the Kalman filter gain because of changes in the atmosphere characteristics, the increase of Telescopes and sensors resolutions and the high sampling rate impose quite strict restrictions to the computational load for computing the Kalman gain. Motivated by the above considerations, some strategies have been recently considered in the system theory and astronomical communities for the efficient computation of the Kalman gain for large AO systems. Specifically, this paper presents some changes to a recently proposed procedure: the proposed approach, which exploits some results in the control theory of distributed systems, computes an approximation of the optimal gain in the frequency domain exploiting the spatial homogeneity of the system. Then, the control strategy takes advantage of some information on the turbulent phase dynamic, that is estimated from the turbulence measurements. Performances of the proposed method are investigated in some simulations.
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ICCA - Multiscale phase screens synthesis based on local PCA
2013 10th IEEE International Conference on Control and Automation (ICCA), 2013Co-Authors: Alessandro Beghi, Angelo Cenedese, Andrea MasieroAbstract:Motivated by the increasing importance of Adaptive Optics (AO) systems for improving the real resolution of large Ground Telescopes, and by the need of testing the AO system performance in realistic working conditions, in this paper we address the problem of simulating the turbulence effect on Ground telescope observations at high resolution. The multiscale approach presented here generalizes that in [3]: First, a relevant computational time reduction is obtained by exploiting a local spatial principal component analysis (PCA) representation of the turbulence. Furthermore, differently from [3], the turbulence at low resolution is modeled as a moving average (MA) process. While in [3] the wind velocity was restricted to be directed along one of the two spatial axes, the approach proposed here allows to evolve the turbulence indifferently in all the directions. In our simulations the proposed procedure reproduces with good accuracy the theoretical statistical characteristics of the turbulent phase.
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ECC - On the estimation of atmospheric turbulence layers for AO systems
2013 European Control Conference (ECC), 2013Co-Authors: Alessandro Beghi, Angelo Cenedese, Andrea MasieroAbstract:In current and next generation of Ground Telescopes, Adaptive Optics (AO) are employed to overcome the detrimental effects induced by the presence of atmospheric turbulence, that strongly affects the quality of data transmission and limits the actual resolution of the overall system. The analysis as well as the prediction of the turbulent phase affecting the light wavefront is therefore of paramount importance to guarantee the effective performance of the AO solution. In this work, a layered model of turbulence is proposed, based on the definition of a Markov-Random-Field whose parameters are determined according to the turbulence statistics. The problem of turbulence estimation is formalized within the stochastic framework and conditions for the identifiability of the turbulence structure (numbers of layers, energies and velocities) are stated. Finally, an algorithm to allow the layer detection and characterization from measurements is designed. Numerical simulations are used to assess the proposed procedure and validate the results, confirming the validity of the approach and the accuracy of the detection.
Alessandro Beghi - One of the best experts on this subject based on the ideXlab platform.
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ECC - Efficient algorithms for the reconstruction and prediction of atmospheric turbulence in AO systems
2014 European Control Conference (ECC), 2014Co-Authors: Alessandro Beghi, Angelo Cenedese, Andrea MasieroAbstract:Technological advances and the ever-growing human quest for improving the resolution of telescope observations are motivating the design of larger and larger Ground Telescopes: indeed, the larger is the telescope lens diameter, the better is the diffraction limited resolution of the telescope. Unfortunately, the terrestrial atmospheric turbulence, if not properly compensated, negatively affects the telescope observations, limiting its real resolution. Adaptive Optics (AO) systems are used in large Ground Telescopes in order to compensate the effect of the atmosphere, and hence to make the real telescope resolution be determined by the diffraction properties of the lens. AO systems exploit the measurements of wavefront sensors to estimate the current values of the atmospheric turbulence, and compensate its effect by properly adapting the shape of a set of deformable mirrors. As the size of the telescope lenses is increasing, then the size of the AO system (e.g. the number of deformable mirror actuators and the size of the wavefront sensor) is increasing as well. This causes the increase of the computational burden needed to compute a proper compensation of the effect of the atmosphere. Consequently, as the potential telescope resolution increases, the task of the AO systems becomes more challenging. Motivated by the need of providing AO solutions useful for the next generations of Ground Telescopes, then a number of efficient algorithms have been recently considered in the literature to solve the problems related to the AO system. This paper considers the combination of a recently proposed very efficient phase reconstruction method, namely the CuRe, with a properly defined Kalman filter in order to obtain a dynamic compensation of the atmospheric turbulence. The performance of the proposed approach is investigated in some simulations.
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Multiscale phase screen synthesis based on local principal component analysis.
Applied optics, 2013Co-Authors: Alessandro Beghi, Angelo Cenedese, Andrea MasieroAbstract:Motivated by the increasing importance of adaptive optics (AO) systems for improving the real resolution of large Ground Telescopes, and by the need of testing the AO system performance in realistic working conditions, in this paper we address the problem of simulating the turbulence effect on Ground telescope observations at high resolution. The procedure presented here generalizes the multiscale stochastic approach introduced in our earlier paper [Appl. Opt.50, 4124 (2011)], with respect to the previous solution, a relevant computational time reduction is obtained by exploiting a local spatial principal component analysis (PCA) representation of the turbulence. Furthermore, the turbulence at low resolution is modeled as a moving average (MA) process, while previously [Appl. Opt.50, 4124 (2011)] the wind velocity was restricted to be directed along one of the two spatial axes, the use of such MA model allows the turbulence to evolve indifferently in all the directions. In our simulations, the proposed procedure reproduces the theoretical statistical characteristics of the turbulent phase with good accuracy.
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CDC - Turbulence modeling and Kalman prediction for the control of large AO systems
52nd IEEE Conference on Decision and Control, 2013Co-Authors: Alessandro Beghi, Angelo Cenedese, Andrea MasieroAbstract:Measurements of large Ground Telescopes are affected by the presence of the terrestrial atmospheric turbulence: local changes of the atmospheric refraction index (e.g. due to wind and temperature variations) cause a non flat surface of the wavefront of light beams incoming on the telescope, thus degrading the quality of the observed images. Adaptive Optics (AO) systems are of fundamental importance to reduce such atmospheric influence on Ground Telescopes and thus to obtain high resolution observations. The goal of the AO system is that of estimating and compensating the atmospheric turbulence effect by properly commanding a set of deformable mirrors. Because of delays in the closed loop system, the Kalman filter plays an important role in ensuring an effective control performance by providing good atmosphere predictions. However, the need of periodically updating the Kalman filter gain because of changes in the atmosphere characteristics, the increase of Telescopes and sensors resolutions and the high sampling rate impose quite strict restrictions to the computational load for computing the Kalman gain. Motivated by the above considerations, some strategies have been recently considered in the system theory and astronomical communities for the efficient computation of the Kalman gain for large AO systems. Specifically, this paper presents some changes to a recently proposed procedure: the proposed approach, which exploits some results in the control theory of distributed systems, computes an approximation of the optimal gain in the frequency domain exploiting the spatial homogeneity of the system. Then, the control strategy takes advantage of some information on the turbulent phase dynamic, that is estimated from the turbulence measurements. Performances of the proposed method are investigated in some simulations.
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ICCA - Multiscale phase screens synthesis based on local PCA
2013 10th IEEE International Conference on Control and Automation (ICCA), 2013Co-Authors: Alessandro Beghi, Angelo Cenedese, Andrea MasieroAbstract:Motivated by the increasing importance of Adaptive Optics (AO) systems for improving the real resolution of large Ground Telescopes, and by the need of testing the AO system performance in realistic working conditions, in this paper we address the problem of simulating the turbulence effect on Ground telescope observations at high resolution. The multiscale approach presented here generalizes that in [3]: First, a relevant computational time reduction is obtained by exploiting a local spatial principal component analysis (PCA) representation of the turbulence. Furthermore, differently from [3], the turbulence at low resolution is modeled as a moving average (MA) process. While in [3] the wind velocity was restricted to be directed along one of the two spatial axes, the approach proposed here allows to evolve the turbulence indifferently in all the directions. In our simulations the proposed procedure reproduces with good accuracy the theoretical statistical characteristics of the turbulent phase.
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ECC - On the estimation of atmospheric turbulence layers for AO systems
2013 European Control Conference (ECC), 2013Co-Authors: Alessandro Beghi, Angelo Cenedese, Andrea MasieroAbstract:In current and next generation of Ground Telescopes, Adaptive Optics (AO) are employed to overcome the detrimental effects induced by the presence of atmospheric turbulence, that strongly affects the quality of data transmission and limits the actual resolution of the overall system. The analysis as well as the prediction of the turbulent phase affecting the light wavefront is therefore of paramount importance to guarantee the effective performance of the AO solution. In this work, a layered model of turbulence is proposed, based on the definition of a Markov-Random-Field whose parameters are determined according to the turbulence statistics. The problem of turbulence estimation is formalized within the stochastic framework and conditions for the identifiability of the turbulence structure (numbers of layers, energies and velocities) are stated. Finally, an algorithm to allow the layer detection and characterization from measurements is designed. Numerical simulations are used to assess the proposed procedure and validate the results, confirming the validity of the approach and the accuracy of the detection.
Angelo Cenedese - One of the best experts on this subject based on the ideXlab platform.
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ECC - Efficient algorithms for the reconstruction and prediction of atmospheric turbulence in AO systems
2014 European Control Conference (ECC), 2014Co-Authors: Alessandro Beghi, Angelo Cenedese, Andrea MasieroAbstract:Technological advances and the ever-growing human quest for improving the resolution of telescope observations are motivating the design of larger and larger Ground Telescopes: indeed, the larger is the telescope lens diameter, the better is the diffraction limited resolution of the telescope. Unfortunately, the terrestrial atmospheric turbulence, if not properly compensated, negatively affects the telescope observations, limiting its real resolution. Adaptive Optics (AO) systems are used in large Ground Telescopes in order to compensate the effect of the atmosphere, and hence to make the real telescope resolution be determined by the diffraction properties of the lens. AO systems exploit the measurements of wavefront sensors to estimate the current values of the atmospheric turbulence, and compensate its effect by properly adapting the shape of a set of deformable mirrors. As the size of the telescope lenses is increasing, then the size of the AO system (e.g. the number of deformable mirror actuators and the size of the wavefront sensor) is increasing as well. This causes the increase of the computational burden needed to compute a proper compensation of the effect of the atmosphere. Consequently, as the potential telescope resolution increases, the task of the AO systems becomes more challenging. Motivated by the need of providing AO solutions useful for the next generations of Ground Telescopes, then a number of efficient algorithms have been recently considered in the literature to solve the problems related to the AO system. This paper considers the combination of a recently proposed very efficient phase reconstruction method, namely the CuRe, with a properly defined Kalman filter in order to obtain a dynamic compensation of the atmospheric turbulence. The performance of the proposed approach is investigated in some simulations.
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Multiscale phase screen synthesis based on local principal component analysis.
Applied optics, 2013Co-Authors: Alessandro Beghi, Angelo Cenedese, Andrea MasieroAbstract:Motivated by the increasing importance of adaptive optics (AO) systems for improving the real resolution of large Ground Telescopes, and by the need of testing the AO system performance in realistic working conditions, in this paper we address the problem of simulating the turbulence effect on Ground telescope observations at high resolution. The procedure presented here generalizes the multiscale stochastic approach introduced in our earlier paper [Appl. Opt.50, 4124 (2011)], with respect to the previous solution, a relevant computational time reduction is obtained by exploiting a local spatial principal component analysis (PCA) representation of the turbulence. Furthermore, the turbulence at low resolution is modeled as a moving average (MA) process, while previously [Appl. Opt.50, 4124 (2011)] the wind velocity was restricted to be directed along one of the two spatial axes, the use of such MA model allows the turbulence to evolve indifferently in all the directions. In our simulations, the proposed procedure reproduces the theoretical statistical characteristics of the turbulent phase with good accuracy.
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CDC - Turbulence modeling and Kalman prediction for the control of large AO systems
52nd IEEE Conference on Decision and Control, 2013Co-Authors: Alessandro Beghi, Angelo Cenedese, Andrea MasieroAbstract:Measurements of large Ground Telescopes are affected by the presence of the terrestrial atmospheric turbulence: local changes of the atmospheric refraction index (e.g. due to wind and temperature variations) cause a non flat surface of the wavefront of light beams incoming on the telescope, thus degrading the quality of the observed images. Adaptive Optics (AO) systems are of fundamental importance to reduce such atmospheric influence on Ground Telescopes and thus to obtain high resolution observations. The goal of the AO system is that of estimating and compensating the atmospheric turbulence effect by properly commanding a set of deformable mirrors. Because of delays in the closed loop system, the Kalman filter plays an important role in ensuring an effective control performance by providing good atmosphere predictions. However, the need of periodically updating the Kalman filter gain because of changes in the atmosphere characteristics, the increase of Telescopes and sensors resolutions and the high sampling rate impose quite strict restrictions to the computational load for computing the Kalman gain. Motivated by the above considerations, some strategies have been recently considered in the system theory and astronomical communities for the efficient computation of the Kalman gain for large AO systems. Specifically, this paper presents some changes to a recently proposed procedure: the proposed approach, which exploits some results in the control theory of distributed systems, computes an approximation of the optimal gain in the frequency domain exploiting the spatial homogeneity of the system. Then, the control strategy takes advantage of some information on the turbulent phase dynamic, that is estimated from the turbulence measurements. Performances of the proposed method are investigated in some simulations.
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ICCA - Multiscale phase screens synthesis based on local PCA
2013 10th IEEE International Conference on Control and Automation (ICCA), 2013Co-Authors: Alessandro Beghi, Angelo Cenedese, Andrea MasieroAbstract:Motivated by the increasing importance of Adaptive Optics (AO) systems for improving the real resolution of large Ground Telescopes, and by the need of testing the AO system performance in realistic working conditions, in this paper we address the problem of simulating the turbulence effect on Ground telescope observations at high resolution. The multiscale approach presented here generalizes that in [3]: First, a relevant computational time reduction is obtained by exploiting a local spatial principal component analysis (PCA) representation of the turbulence. Furthermore, differently from [3], the turbulence at low resolution is modeled as a moving average (MA) process. While in [3] the wind velocity was restricted to be directed along one of the two spatial axes, the approach proposed here allows to evolve the turbulence indifferently in all the directions. In our simulations the proposed procedure reproduces with good accuracy the theoretical statistical characteristics of the turbulent phase.
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ECC - On the estimation of atmospheric turbulence layers for AO systems
2013 European Control Conference (ECC), 2013Co-Authors: Alessandro Beghi, Angelo Cenedese, Andrea MasieroAbstract:In current and next generation of Ground Telescopes, Adaptive Optics (AO) are employed to overcome the detrimental effects induced by the presence of atmospheric turbulence, that strongly affects the quality of data transmission and limits the actual resolution of the overall system. The analysis as well as the prediction of the turbulent phase affecting the light wavefront is therefore of paramount importance to guarantee the effective performance of the AO solution. In this work, a layered model of turbulence is proposed, based on the definition of a Markov-Random-Field whose parameters are determined according to the turbulence statistics. The problem of turbulence estimation is formalized within the stochastic framework and conditions for the identifiability of the turbulence structure (numbers of layers, energies and velocities) are stated. Finally, an algorithm to allow the layer detection and characterization from measurements is designed. Numerical simulations are used to assess the proposed procedure and validate the results, confirming the validity of the approach and the accuracy of the detection.
Alessandro Chiuso - One of the best experts on this subject based on the ideXlab platform.
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Dynamic Calibration of Adaptive Optics Systems: A System Identification Approach
IEEE Transactions on Control Systems Technology, 2010Co-Authors: Alessandro Chiuso, Riccardo Muradore, Enrico MarchettiAbstract:Adaptive optics is used in astronomy to obtain high resolution images, close to diffraction limited, of stars and galaxies with Ground Telescopes, otherwise blurred by atmospheric turbulence. The measurements of one or more wavefront sensor are used to flatten distorted wavefronts with one or more deformable mirror in a feedback loop. In this brief, we shall report our experience on the problem of building an accurate (dynamical) model of the actuation (deformable mirror) and sensing (wavefront sensor) of adaptive optics system. This will be done adapting state-of-the-art system identification and model reduction techniques to the problem at hand. Our results are based on real data collected under various operating conditions from a demonstrator developed at the European Southern Observatory (ESO), which is now operating in the Paranal Observatory (Chile).
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CDC - Sparse calibration of an extreme Adaptive Optics system
49th IEEE Conference on Decision and Control (CDC), 2010Co-Authors: Alessandro Chiuso, Riccardo Muradore, Emmanuel Aller-carpentierAbstract:Adaptive optics systems are extensively used in astronomy to obtain high resolution pictures of stars and galaxies with Ground Telescopes. The crucial point is to shape deformable mirrors in order to compensate for the incoming wave distorted by the atmospheric turbulence. The calibration of the system is the cornerstone to obtain good performance. The next generation of adaptive optics system, eXtreme Adaptive Optics (XAO), will have a very large number of actuators and sensors (∼ 104) in order to guarantee high Strehl ratio and contrast levels; as such computational burden could become a serious bottleneck. For this reason several iterative methods have been proposed in the last decade. Since convergence and computational complexity of these methods depend on the sparsity of the interaction matrix (matrix projecting commands into measurements), the problem of calibrating an XAO system forcing the interaction matrix to be as sparse as possible is clearly important. In this paper we propose a method based on the LASSO regression algorithm that solves efficiently this problem.
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CDC - Dynamic calibration of adaptive optics systems: A system identification approach
2008 47th IEEE Conference on Decision and Control, 2008Co-Authors: Alessandro Chiuso, Riccardo Muradore, Enrico MarchettiAbstract:Adaptive optics is used in astronomy to obtain high resolution images, close to diffraction limited, of stars and galaxies with Ground Telescopes, otherwise blurred by atmospheric turbulence. The measurements of one or more wavefront sensor are used to flatten distorted wavefronts with one or more deformable mirror in a feedback loop. In this paper we shall report our experience on the problem of building an accurate (dynamical) model of the actuation (deformable mirror) and sensing (wavefront sensor) of adaptive optics system. This will be done adapting state-of-the-art system identification and model reduction techniques to the problem at hand. Our results are based on real data collected under various operating conditions from a demonstrator developed at the European Southern Observatory (ESO), which is now operating in the Paranal observatory (Chile).
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ACC - Adaptive Optics Systems: A Challenge for Closed Loop Subspace Identifcation
2007 American Control Conference, 2007Co-Authors: Alessandro Chiuso, Riccardo Muradore, Enrico FedrigoAbstract:Adaptive optics allows to obtain pictures of the sky (stars and galaxies) on Ground Telescopes with a resolution close to those obtained from Telescopes outside the atmosphere, for example the Hubble telescope. This requires controlling a deformable mirror in order to compensate for the distortion introduced by the atmosphere. In this paper the problem of obtaining a model based on which controllers can be designed is discussed. This problem is particularly challenging for many reasons, among which the high dimensions of the input and output spaces. The system has 60 inputs (piezoelectric actuators on the mirror) and 60 outputs (avalanches photodiodes sensing the wavefront "slope"). Some promising preliminary results are reported using a recently developed subspace method which allows identification to be performed in closed loop.
Enrico Marchetti - One of the best experts on this subject based on the ideXlab platform.
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Dynamic Calibration of Adaptive Optics Systems: A System Identification Approach
IEEE Transactions on Control Systems Technology, 2010Co-Authors: Alessandro Chiuso, Riccardo Muradore, Enrico MarchettiAbstract:Adaptive optics is used in astronomy to obtain high resolution images, close to diffraction limited, of stars and galaxies with Ground Telescopes, otherwise blurred by atmospheric turbulence. The measurements of one or more wavefront sensor are used to flatten distorted wavefronts with one or more deformable mirror in a feedback loop. In this brief, we shall report our experience on the problem of building an accurate (dynamical) model of the actuation (deformable mirror) and sensing (wavefront sensor) of adaptive optics system. This will be done adapting state-of-the-art system identification and model reduction techniques to the problem at hand. Our results are based on real data collected under various operating conditions from a demonstrator developed at the European Southern Observatory (ESO), which is now operating in the Paranal Observatory (Chile).
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CDC - Dynamic calibration of adaptive optics systems: A system identification approach
2008 47th IEEE Conference on Decision and Control, 2008Co-Authors: Alessandro Chiuso, Riccardo Muradore, Enrico MarchettiAbstract:Adaptive optics is used in astronomy to obtain high resolution images, close to diffraction limited, of stars and galaxies with Ground Telescopes, otherwise blurred by atmospheric turbulence. The measurements of one or more wavefront sensor are used to flatten distorted wavefronts with one or more deformable mirror in a feedback loop. In this paper we shall report our experience on the problem of building an accurate (dynamical) model of the actuation (deformable mirror) and sensing (wavefront sensor) of adaptive optics system. This will be done adapting state-of-the-art system identification and model reduction techniques to the problem at hand. Our results are based on real data collected under various operating conditions from a demonstrator developed at the European Southern Observatory (ESO), which is now operating in the Paranal observatory (Chile).
