Green Light for the WHT

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Green Light for the WHT. Overview. GLAS : G round-layer L aser A daptive optics S ystem. Science drivers AO Infrastructure at WHT GLAS technicalities Current status of development. Strategic Considerations. GLAS is only major project on WHT for the next few years - PowerPoint PPT Presentation

Transcript of Green Light for the WHT

  • Overview Science drivers

    AO Infrastructure at WHT

    GLAS technicalities

    Current status of developmentGLAS: Ground-layer Laser Adaptive optics System

  • GLAS is only major project on WHT for the next few years

    Overall top objective: = Increasing sky coverage, approaching 100% = Niche: Integral Field Spectroscopy from 0.6 - 1m = Ground-layer correction: not highest Strehl, but scientifically useful correction = Aim for easy operation keep (relatively) simple

    Rayleigh option for cost & operational reasons

    Strategic Considerations

  • Why on a 4-m telescope ? Big enough to produce exciting science

    Exploit good seeing on La Palma

    Prospect of large science programmes

    Complement large telescopes

    Cost effective

    Natural seeing NAOMI AO in I band

  • Sky coverage expectationsR = 18 & search field of 2 arcmin diameterThank-youRemko !

  • Ground layer turbulenceJimenez & IAC team, 2004

  • Performance expectationsPSF specifications using R=17th mag tip-tilt star(R=18 goal) in median seeing conditions

    RIJHUncorrected0.610.580.530.51Corrected0.300.200.110.11

  • AO corrects 2D PSF IFS can fully exploit increased resolution

    Integral field spectroscopy

  • (Becker et al, astro-ph/0311315)Crowded field spectroscopy

  • Infrastructure

  • Goal beacon

    20 km

    turbulence

    laserLaser beacon at fixed distance of 20km, of 200m depth.

    Laser beam will remain always on-axis.

    Laser wavelength primarily defined by availability of affordable quality solid-state lasers.

  • System diagram

  • The laserSolid state, diode-pumped Yb-YAG disk laserWavelength: 515nmOutput power: 30WBeam quality: M2 < 1.1Q-switched, 400ns pulse

  • Laser location

  • Beam launch telescope

  • Wavefront sensor shutter

  • Wavefront sensor8 x 8 Shack-HartmanMatched to DM2 arcsec wide aperturesMax. elongation 0.2 arcsec

  • WFS detectorsStandard CCD39 for LGSL3CCD for NGS: ~zero read noise gives 1-2 mag advantageLGS loop speed 300 HzNGS loop speed 100 Hz

  • MILESTONEDATEKick-off meetingApr 2004 Preliminary Design Review Jan 2005 Final Design Review Aug 2005Lab verification of sub systems May 2006Science verification Sep 2006Operation Oct 2006 Schedule