Experimental Astronomy

, Volume 19, Issue 1, pp 103–109

The Ultimate CCD for Laser Guide Star Wavefront Sensing on Extremely Large Telescopes

  • James W. Beletic
  • Sean Adkins
  • Barry Burke
  • Robert Reich
  • Bernie Kosicki
  • Vyshnavi Suntharalingham
  • Charlie Bleau
  • Ray DuVarney
  • Richard Stover
  • Jerry Nelson
  • Francois Rigaut
Article

DOI: 10.1007/s10686-005-9012-3

Cite this article as:
Beletic, J.W., Adkins, S., Burke, B. et al. Exp Astron (2005) 19: 103. doi:10.1007/s10686-005-9012-3

Abstract

All of the extremely large telescopes (ELTs) will utilize sodium laser guide star (LGS) adaptive optics (AO) systems. Most of these telescopes plan to use the Shack-Hartmann approach for wavefront sensing. In these AO systems, the laser spots in subapertures at the edge of the pupil will suffer from spot elongation due to the 10 km extent of the sodium layer and the large separation from the projection laser. This spot elongation will severely degrade the performance of standard geometry wavefront sensing systems. In this paper, we present a CCD with custom pixel morphology that aligns the pixels of each subaperture with the radial extension of the LGS spot. This CCD design will give better performance than a standard geometry CCDs for continuous wave lasers. In addition, this CCD design is optimal for a pulsed sodium laser. The pixel geometry enables each subaperture to follow a laser pulse traversing the sodium layer, providing optimal sampling of a limited number of detected photons. In addition to novel pixel layout, this CCD will also incorporate experimental JFET sense amplifiers and use CMOS design approaches to simplify the routing of biases, clocks and video output. This CCD will attain photon-noise limited performance at high frame rates, and is being incorporated in the plans for the Thirty Meter Telescope (TMT).

Keywords

CCDCMOS design conceptsELTShack-Hartmann wavefront sensingsodium laser guide star

Copyright information

© Springer Science+Business Media, Inc. 2006

Authors and Affiliations

  • James W. Beletic
    • 1
  • Sean Adkins
    • 2
  • Barry Burke
    • 3
  • Robert Reich
    • 3
  • Bernie Kosicki
    • 3
  • Vyshnavi Suntharalingham
    • 3
  • Charlie Bleau
    • 4
  • Ray DuVarney
    • 4
  • Richard Stover
    • 5
  • Jerry Nelson
    • 6
  • Francois Rigaut
    • 7
  1. 1.Rockwell Scientific CompanyThousand OaksUSA
  2. 2.W.M. Keck ObservatoryMauna KeaUSA
  3. 3.MIT Lincoln LaboratoryLexingtonUSA
  4. 4.SciMeasure Analytical SystemsAtlantaUSA
  5. 5.Lick ObservatorySanta CruzUSA
  6. 6.University of CaliforniaSanta CruzUSA
  7. 7.Gemini ObservatoryHiloUSA