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Tilt anisoplanatism and PSF retrieval in LGS MCAO using a predictive controller

Flicker, Ralf LU and Rigaut, François (2002) Beyond conventional adaptive optics : a conference devoted to the adaptive optics for extremely large telescopes. Proceedings of the Topical Meeting In Beyond conventional adaptive optics : ESO Conference and Workshop Proceedings 58. p.377-377
Abstract
It is shown how tilt anisoplanatism in laser-supported multi-conjugatedadaptive optics (MCAO) systems can be a) predicted from a prioriknowledge, b) compensated using additional natural guide stars (NGS),and c) estimated in real time from control loop data to allow PSFretrieval. As a consequence of the problems associated with retrievingatmospheric tip and tilt from laser guide star (LGS) measurements, anMCAO system without additional reference beacons will have a set of nullmodes that can not be measured by the LGS. These are the global tip andtilt modes, and three plate scale modes deriving principally fromtomographical combinations of quadratic modes (focus and astigmatisms).These modes can be compensated by introducing a NGS-supported... (More)
It is shown how tilt anisoplanatism in laser-supported multi-conjugatedadaptive optics (MCAO) systems can be a) predicted from a prioriknowledge, b) compensated using additional natural guide stars (NGS),and c) estimated in real time from control loop data to allow PSFretrieval. As a consequence of the problems associated with retrievingatmospheric tip and tilt from laser guide star (LGS) measurements, anMCAO system without additional reference beacons will have a set of nullmodes that can not be measured by the LGS. These are the global tip andtilt modes, and three plate scale modes deriving principally fromtomographical combinations of quadratic modes (focus and astigmatisms).These modes can be compensated by introducing a NGS-supported null modecontrol loop totally decoupled from the LGS system. Invoking a prioriassumptions about the atmospheric turbulence, we compute the loss ofStrehl ratio from residual tilt anisoplanatism due to noise and servolag for some sample NGS configurations and magnitudes. PSF retrieval isdemonstrated in all cases. Results are obtained and compared using botha simple and a noise-weighted least squares estimator, and both anintegrating and a predictive linear controller. Finally, a method forreal time estimation is presented, and verification by monte carlogenerated loop data is work in progress. (Less)
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Chapter in Book/Report/Conference proceeding
publication status
published
subject
in
Beyond conventional adaptive optics : ESO Conference and Workshop Proceedings
editor
Vernet, E; Ragazzoni, S; Esposito, S; Hubin, N; ; ; and
volume
58
pages
377 - 377
publisher
European Southern Observatory
conference name
Beyond conventional adaptive optics : a conference devoted to the adaptive optics for extremely large telescopes. Proceedings of the Topical Meeting
ISBN
3923524617
language
English
LU publication?
yes
id
180f25e8-0878-4535-abd2-678d16043cf3 (old id 528019)
date added to LUP
2007-09-17 13:00:33
date last changed
2016-04-16 09:53:24
@inproceedings{180f25e8-0878-4535-abd2-678d16043cf3,
  abstract     = {It is shown how tilt anisoplanatism in laser-supported multi-conjugatedadaptive optics (MCAO) systems can be a) predicted from a prioriknowledge, b) compensated using additional natural guide stars (NGS),and c) estimated in real time from control loop data to allow PSFretrieval. As a consequence of the problems associated with retrievingatmospheric tip and tilt from laser guide star (LGS) measurements, anMCAO system without additional reference beacons will have a set of nullmodes that can not be measured by the LGS. These are the global tip andtilt modes, and three plate scale modes deriving principally fromtomographical combinations of quadratic modes (focus and astigmatisms).These modes can be compensated by introducing a NGS-supported null modecontrol loop totally decoupled from the LGS system. Invoking a prioriassumptions about the atmospheric turbulence, we compute the loss ofStrehl ratio from residual tilt anisoplanatism due to noise and servolag for some sample NGS configurations and magnitudes. PSF retrieval isdemonstrated in all cases. Results are obtained and compared using botha simple and a noise-weighted least squares estimator, and both anintegrating and a predictive linear controller. Finally, a method forreal time estimation is presented, and verification by monte carlogenerated loop data is work in progress.},
  author       = {Flicker, Ralf and Rigaut, François},
  booktitle    = {Beyond conventional adaptive optics : ESO Conference and Workshop Proceedings},
  editor       = {Vernet, E and Ragazzoni, S and Esposito, S and Hubin, N},
  isbn         = {3923524617},
  language     = {eng},
  pages        = {377--377},
  publisher    = {European Southern Observatory},
  title        = {Tilt anisoplanatism and PSF retrieval in LGS MCAO using a predictive controller},
  volume       = {58},
  year         = {2002},
}