Thesis

Fast wave-front reconstructors for Astronomical Adaptive Optics in the spatial-frequency domain

• Call:

  IDPASC Portugal - PHD Programme 2014

• Academic Year:

  2014 /2015

• Domains:

• Supervisor:

  Carlos M Correia

• Co-Supervisor:

  Thierry Fusco

• Institution:

  Universidade do Porto

• Host Institution:

  Laboratoire d'Astrophysique de Marseille and SIM/FEUP

• Abstract:

  The European Extremely Large Telescope (E-ELT) is a ground-breaking project for a 39m diameter ground-based optical/NIR telescope with unprecedented scientific goals and system complexity. Portugal has recently joined as a member. Unlike current telescopes, the E-ELT is fully adaptive, since its optical elements adapt in real-time to changing observing conditions. The European Southern Observatory (ESO) leads and manages the overall E-ELT project development. Portugal is an ESO member for over a decade now. Light propagating through the atmosphere is bent due to local variations of the index of refraction, the consequence of which are blurred images where the angular resolution – the power to distinguish light from 2 different sources apart – is severely damaged. Adaptive Optics systems use a set of wave-front sensors to measure the distorted wave-fronts, deformable mirrors to put it back to a planar shape and a real-time computer that estimates the wave-fronts from measurements. This is done both in a single direction (classical AO) or in the atmospheric volume (tomographic AO). The wave-front reconstruction, name by which is known the inverse problem of estimating the wave-front from the measurements involves massive computation, in particular for E-ELT-sized AO systems. Recent progress in real-time implementation of wave-front reconstructors for adaptive optics applications have shown the huge potential for spatial-frequency domain techniques – or commonly called Fourier-domain techniques – for they scale much slower than conventional vector-matrix multiplies used hitherto to solve linear systems of equations or the order 10k squared or so. Of particular interest for wide-field and extreme adaptive optics alike, Fourier-domain reconstructors have been developed in the last decade and are now ripe for further testing and implementation. There are still some shortcomings mainly emanating from the incomplete forward model that neglects several error terms. This project has three major components: 1) high-performance computing simulations with the analytical development of a novel approach to remove remaining errors after reconstruction 2) extend results to the pyramid wave-front sensor in tight collaboration with Italian partners 3) implementation and test on an Adaptive Optics optical bench at LAM – Laboratoire d'Astrophysique de Marseille. Profile: Student with strong interest in astronomy, mathematical modelling, numerical simulations, data/signal processing, statistical methods, optics. Availability for extended missions in Marseille is required. References C. Correia et al, Anti-aliasing Wiener filtering for wave-front reconstruction in the spatial-frequency domain in adaptive-optics-assited astronomical high-contrast imaging instruments JOSA-A, submitted (Jul 2014) C. Correia, C. Kulcsar, J-M. Conan and H.-F. Raynaud, Hartmann modelling in the Fourier domain; Application to real-time reconstruction in Adaptive Optics, Proceedings of the SPIE - Ground-based Astronomical Instrumentation, Volume 7015, 2008. http://dx.doi.org/10.1117/12.788455