Thesis

Turbulence profilometry for high-resolution astronomical adaptive optics

• Call:

  IDPASC Portugal - PHD Programme 2015

• Academic Year:

  2015 / 2016

• Domain:

  Astrophysics

• Supervisor:

  Carlos M Correia

• Co-Supervisor:

  Paulo Garcia

• Institution:

  Universidade do Porto

• Host Institution:

  FEUP

• Abstract:

  Adaptive Optics (AO) is a technique that currently equips most of the ground-based astronomical telescopes of classes 3-10m and will be at the heart of the future 20-40m-class telescopes. AO enables to correct the effects induced by atmospheric turbulence, which affect the telescopes’ resolution and hence image quality. Introduced in the 1990s, AO systems became tomographic, allowing the analysis of the 3D volumetric turbulence needed to achieve wide-field correction. Tomography is a linear, compute-intensive process requiring inverse-problem solvers. Bayesian approaches reach optimality but are deeply dependent on knowledge of the turbulence strength, scale, layer number and location, wind-speeds, etc along the lines of sight. Such parameters are commonly identified from optical data (scintillation, wave-front gradients) exploiting the angular correlation of signals – SCIDAR and SLODAR-like methods. Tomographic AO systems offer a wealth of information from which an enhanced processing can be envisaged. The precision required for next-generation instrumentation is also challenging to achieve. A promising method to be used complementary to the built-in SLODAR method consists in the enhancement of existing identification algorithms using principles of synchronous detection in the spatial-frequency domain and its generalisation to tomographic, multi-sensor systems. Applications foreseen are for Multi-Object AO systems – in particular Raven the science and technology demonstrator installed at the Subaru 8m telescope – and in general for wide-field AO systems and planet imagers ahead of the 39m diameter European Extremely Large Telescope to be in operation in the next decade. Profile: Student with strong interest in mathematical modelling, statistical physics, numerical simulations, data/signal processing. References: C. Correia et al, Static and predictive tomographic reconstruction for wide-field multi-object adaptive optics systems, JOSA-A 2014 http://dx.doi.org/10.1364/JOSAA.31.000101 Olivier Lardière, David R. Andersen, Colin Bradley, Kate J. Jackson, Reston Nash, Darryl Gamroth, Célia Blain, Przemek Lach, Jean-Pierre Véran, Shin Oya, Yoshito Ono, Carlos M. Correia, Kim Venn, Yutaka Hayano, Hiroshi Terada, Masayuki Akiyama, Multi-object adaptive optics on-sky results with Raven SPIE Astronomical Telescopes + Instrumentation, Jun 2014, http://dx.doi.org/10.1117/12.2055480