Performance of keck adaptive optics with sodium laser guide star

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The Keck telescope adaptive optics system is designed to optimize performance in he 1 to 3 micron region of observation wavelengths (J, H, and K astronomical bands). The system uses a 249 degree of freedom deformable mirror, so that the interactuator spacing is 56 cm as mapped onto the 10 meter aperture. 56 cm is roughly equal to r0 at 1.4 microns, which implies the wavefront fitting error is 0.52 ({lambda}/2{pi})({ital d}/{ital r}{sub 0}){sup 5/6} = 118 nm rms. This is sufficient to produce a system Strehl of 0.74 at 1.4 microns if all other sources of error are negligible, ... continued below

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4 p.

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Gavel, D.T.; Olivier, S. & Brase, J. March 8, 1996.

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The Keck telescope adaptive optics system is designed to optimize performance in he 1 to 3 micron region of observation wavelengths (J, H, and K astronomical bands). The system uses a 249 degree of freedom deformable mirror, so that the interactuator spacing is 56 cm as mapped onto the 10 meter aperture. 56 cm is roughly equal to r0 at 1.4 microns, which implies the wavefront fitting error is 0.52 ({lambda}/2{pi})({ital d}/{ital r}{sub 0}){sup 5/6} = 118 nm rms. This is sufficient to produce a system Strehl of 0.74 at 1.4 microns if all other sources of error are negligible, which would be the case with a bright natural guidestar and very high control bandwidth. Other errors associated with the adaptive optics will however contribute to Strehl degradation, namely, servo bandwidth error due to inability to reject all temporal frequencies of the aberrated wavefront, wavefront measurement error due to finite signal-to-noise ratio in the wavefront sensor, and, in the case of a laser guidestar, the so-called cone effect where rays from the guidestar beacon fail to sample some of the upper atmosphere turbulence. Cone effect is mitigated considerably by the use of the very high altitude sodium laser guidestar (90 km altitude), as opposed to Rayleigh beacons at 20 km. However, considering the Keck telescope`s large aperture, this is still the dominating wavefront error contributor in the current adaptive optics system design.

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4 p.

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OSTI as DE96014132

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  • OSA/IEEE-LEOS/SPIE summer topical meeting on adaptive optics, international symposium on optical memory and optical data storage and topical meeting on nonlinear optics: materials, fundamentals and applications, Maui, HI (United States), 8-12 Jul 1996

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  • Other: DE96014132
  • Report No.: UCRL-JC--123529
  • Report No.: CONF-9607118--1
  • Grant Number: W-7405-ENG-48
  • Office of Scientific & Technical Information Report Number: 377539
  • Archival Resource Key: ark:/67531/metadc685666

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  • March 8, 1996

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  • July 25, 2015, 2:20 a.m.

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  • Feb. 17, 2016, 3:18 p.m.

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Gavel, D.T.; Olivier, S. & Brase, J. Performance of keck adaptive optics with sodium laser guide star, article, March 8, 1996; California. (digital.library.unt.edu/ark:/67531/metadc685666/: accessed December 12, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.