OverviewOverview

Science drivers

AO Infrastructure at WHT

GLAS technicalities

Current status of development

GLAS: 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 - 1μm

= Ground-layer correction:

not highest Strehl, but scientifically useful correction

= Aim for easy operation – keep (relatively) simple

Rayleigh option for cost & operational reasons

Strategic ConsiderationsStrategic Considerations

Why on a 4-m telescope ?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

0.37”

Natural seeing NAOMI AO in I band

Sky coverage expectationsSky coverage expectations

R = 18 & search field of 2 arcmin diameter

Thank-you

Remko !

Ground layer turbulenceGround layer turbulence

Jimenez & IAC team, 2004

Performance expectationsPerformance expectations

R I J H

Uncorrected 0.61 0.58 0.53 0.51

Corrected 0.30 0.20 0.11 0.11

PSF specifications using R=17th mag tip-tilt star

(R=18 goal) in median seeing conditions

AO corrects 2D PSF

IFS can fully exploit

increased resolution

Integral field spectroscopyIntegral field spectroscopy

Multiple band-pass

• Sources confused• Effective spatial

resolution is low=

Broad band-pass

‘Monochromatic’ data-cube slices• Separate star

from gas• Effective spatial

resolution increased• Additional spectral

separation(Becker et al, astro-ph/0311315)

Crowded field spectroscopyCrowded field spectroscopy

InfrastructureInfrastructure

GoalGoal

beacon

20 km

turbulence

laser

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.

System diagramSystem diagram

The laserThe laser

Solid state, diode-pumped

Yb-YAG ‘disk’ laser

Wavelength: 515nm

Output power: 30W

Beam quality: M2 < 1.1

Q-switched, 400ns pulse

Laser locationLaser location

Beam launch telescopeBeam launch telescope

Wavefront sensor shutterWavefront sensor shutter

Wavefront sensorWavefront sensor

8 x 8 Shack-Hartman

Matched to DM

2 arcsec wide apertures

Max. elongation 0.2 arcsec

WFS detectorsWFS 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

ScheduleSchedule

MILESTONEMILESTONE DATEDATE

Kick-off meetingKick-off meeting Apr 2004 Apr 2004

Preliminary Design Review Preliminary Design Review Jan 2005 Jan 2005

Final Design Review Final Design Review Aug 2005Aug 2005

Lab verification of sub systems Lab verification of sub systems May 2006May 2006

Science verification Science verification Sep 2006Sep 2006

Operation Operation Oct 2006Oct 2006