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Effects of atmospheric dispersion on the PSF background level

Owner-Petersen, Mette (2006) Astronomical Telescopes and Instrumentation - Advances in Adaptive Optics II, 2006 6272 II. p.839-846
Abstract
Atmospheric dispersion represents a relatively overlooked problem in connection with the ultimate quality of ELT images corrected by adaptive optics (AO). The aim of this paper is to evaluate the contribution from atmospheric dispersion to the background level of the point-spread function (PSF). Since proper suppression of this level is important for the prospects for direct exo-planet observation, it is necessary to quantify the contributions from all possible sources to it. Atmospheric dispersion will in principle result in three different kinds of contributions. The first one is related to the fact that two rays of different color following the same path through the atmosphere to the telescope do not have the same optical path-length... (More)
Atmospheric dispersion represents a relatively overlooked problem in connection with the ultimate quality of ELT images corrected by adaptive optics (AO). The aim of this paper is to evaluate the contribution from atmospheric dispersion to the background level of the point-spread function (PSF). Since proper suppression of this level is important for the prospects for direct exo-planet observation, it is necessary to quantify the contributions from all possible sources to it. Atmospheric dispersion will in principle result in three different kinds of contributions. The first one is related to the fact that two rays of different color following the same path through the atmosphere to the telescope do not have the same optical path-length difference (OPD). The second one is related to the fact that two coinciding rays of different color entering the atmosphere at a non zero zenith angle will be separated due to refraction before they reach the telescope. The third one is related to the fact that rays are diffracted by inhomogeneities in the atmosphere and that the diffraction angle is dependent on color. This last effect is small<sup>[2]</sup> and will not be treated here. As a consequence of dispersion phase fluctuations can, in principle, only be compensated at a single wavelength by AO systems with deformable mirrors (DMs). Hence looking for an exo-planet in a certain spectral bandwidth there will be a contribution from the parent star uncorrected background level. Hence it will be crucial to perform observations in a narrow spectral bandwidth and to ensure that the wavefront measurements used for AO correction are performed within the same narrow bandwidth. The last point affects the needed magnitude of the parent star, which is used for wavefront measurements. (Less)
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author
organization
publishing date
type
Chapter in Book/Report/Conference proceeding
publication status
published
subject
keywords
Optical path length difference (OPD), Point spread function (PSF), Extremely large telescopes, Atmospheric dispersion
host publication
Proceedings of SPIE - The International Society for Optical Engineering
volume
6272 II
pages
839 - 846
publisher
International Society for Optical Engineering
conference name
Astronomical Telescopes and Instrumentation - Advances in Adaptive Optics II, 2006
conference location
Orlando, FL, United States
conference dates
2006-05-24 - 2006-05-31
external identifiers
  • wos:000240348301020
  • scopus:33749388732
ISSN
0277-786X
1996-756X
DOI
10.1117/12.671481
language
English
LU publication?
yes
id
a24f2a8c-ff4e-4df2-bf7a-84868e530c7d (old id 616739)
date added to LUP
2016-04-01 11:48:03
date last changed
2021-02-17 04:25:52
@inproceedings{a24f2a8c-ff4e-4df2-bf7a-84868e530c7d,
  abstract     = {Atmospheric dispersion represents a relatively overlooked problem in connection with the ultimate quality of ELT images corrected by adaptive optics (AO). The aim of this paper is to evaluate the contribution from atmospheric dispersion to the background level of the point-spread function (PSF). Since proper suppression of this level is important for the prospects for direct exo-planet observation, it is necessary to quantify the contributions from all possible sources to it. Atmospheric dispersion will in principle result in three different kinds of contributions. The first one is related to the fact that two rays of different color following the same path through the atmosphere to the telescope do not have the same optical path-length difference (OPD). The second one is related to the fact that two coinciding rays of different color entering the atmosphere at a non zero zenith angle will be separated due to refraction before they reach the telescope. The third one is related to the fact that rays are diffracted by inhomogeneities in the atmosphere and that the diffraction angle is dependent on color. This last effect is small&lt;sup&gt;[2]&lt;/sup&gt; and will not be treated here. As a consequence of dispersion phase fluctuations can, in principle, only be compensated at a single wavelength by AO systems with deformable mirrors (DMs). Hence looking for an exo-planet in a certain spectral bandwidth there will be a contribution from the parent star uncorrected background level. Hence it will be crucial to perform observations in a narrow spectral bandwidth and to ensure that the wavefront measurements used for AO correction are performed within the same narrow bandwidth. The last point affects the needed magnitude of the parent star, which is used for wavefront measurements.},
  author       = {Owner-Petersen, Mette},
  booktitle    = {Proceedings of SPIE - The International Society for Optical Engineering},
  issn         = {0277-786X},
  language     = {eng},
  pages        = {839--846},
  publisher    = {International Society for Optical Engineering},
  title        = {Effects of atmospheric dispersion on the PSF background level},
  url          = {http://dx.doi.org/10.1117/12.671481},
  doi          = {10.1117/12.671481},
  volume       = {6272 II},
  year         = {2006},
}