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
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