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Green Light for the WHT

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

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Green Light for the WHT

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  1. Green Light for the WHT

  2. Overview GLAS: Ground-layer Laser Adaptive optics System • Science drivers • AO Infrastructure at WHT • GLAS technicalities • Current status of development

  3. Strategic Considerations • 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 - 1μm = Ground-layer correction: not highest Strehl, but scientifically useful correction = Aim for easy operation – keep (relatively) simple • Rayleigh option for cost & operational reasons

  4. 0.37” 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

  5. Sky coverage expectations • R = 18 & search field of 2 arcmin diameter Thank-you Remko !

  6. Ground layer turbulence Jimenez & IAC team, 2004

  7. Performance expectations PSF specifications using R=17th mag tip-tilt star (R=18 goal)in median seeing conditions

  8. Integral field spectroscopy • AO corrects 2D PSF IFS can fully exploit increased resolution

  9. Multiple band-pass Broad band-pass • Sources confused • Effective spatial resolution is low = ‘Monochromatic’ data-cube slices • Separate star from gas • Effective spatial resolution increased • Additional spectral separation Crowded field spectroscopy (Becker et al, astro-ph/0311315)

  10. Infrastructure

  11. Goal • Laser 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. beacon 20 km turbulence laser

  12. System diagram

  13. The laser • Solid state, diode-pumped Yb-YAG ‘disk’ laser • Wavelength: 515nm • Output power: 30W • Beam quality: M2 < 1.1 • Q-switched, 400ns pulse

  14. Laser location

  15. Beam launch telescope

  16. Wavefront sensor shutter

  17. Wavefront sensor • 8 x 8 Shack-Hartman • Matched to DM • 2 arcsec wide apertures • Max. elongation 0.2 arcsec

  18. WFS detectors • Standard CCD39 for LGS • L3CCD for NGS: ~zero read noise gives 1-2 mag advantage • LGS loop speed 300 Hz • NGS loop speed 100 Hz

  19. Schedule MILESTONEDATE • Kick-off meeting Apr 2004 • Preliminary Design Review Jan 2005 • Final Design Review Aug 2005 • Lab verification of sub systems May 2006 • Science verification Sep 2006 • Operation Oct 2006

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