Speckle lifetime in high-contrast adaptive optics

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The main noise source in detection of faint companions such as extrasolar planets near bright stars with AO is speckle noise - residual PSF structure caused by wavefront errors due to the atmosphere, the AO system, and static optical effects. Of these, the most fundamental are atmospheric speckles - even given infinite wavefront SNR and a perfect DM, timelag between sensing and correction will always lead to a residual atmospheric speckle pattern. There have been several suggestions as to the lifetime of these atmospheric speckles, none strongly supported by theory or simulation. We have carried out a systematic series of ... continued below

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Macintosh, B; Poyneer, L; Sivaramakrishnan, A & Marois, C August 19, 2005.

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The main noise source in detection of faint companions such as extrasolar planets near bright stars with AO is speckle noise - residual PSF structure caused by wavefront errors due to the atmosphere, the AO system, and static optical effects. Of these, the most fundamental are atmospheric speckles - even given infinite wavefront SNR and a perfect DM, timelag between sensing and correction will always lead to a residual atmospheric speckle pattern. There have been several suggestions as to the lifetime of these atmospheric speckles, none strongly supported by theory or simulation. We have carried out a systematic series of simulations and analysis to explore this question. We show that speckles have different behavior in the regime in which diffraction is significant (first-order speckles, which are rapidly modulated as a phase error translates across the aperture) and in the coronagraphic regime (second-order speckles, which evolve only as the phase screen completely clears the aperture). We use simulations to analyze the behavior of speckles in a variety of regimes, showing that the second-order atmospheric speckle lifetime is almost constant irrespective of the properties of the AO system, and is set primarily by the atmospheric clearing time of the telescope aperture.

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PDF-file: 10 pages; size: 0.7 Mbytes

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  • Presented at: SPIE Conference on Astronomical Adaptive Optics Systems and Applications II, San Diego, CA, United States, Jul 31 - Aug 04, 2005

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  • Report No.: UCRL-CONF-214737
  • Grant Number: W-7405-ENG-48
  • Office of Scientific & Technical Information Report Number: 875947
  • Archival Resource Key: ark:/67531/metadc881108

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  • August 19, 2005

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  • Sept. 21, 2016, 2:29 a.m.

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  • Dec. 2, 2016, 12:25 p.m.

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Macintosh, B; Poyneer, L; Sivaramakrishnan, A & Marois, C. Speckle lifetime in high-contrast adaptive optics, article, August 19, 2005; Livermore, California. (digital.library.unt.edu/ark:/67531/metadc881108/: accessed August 24, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.