Lorentz Center - Ground Layer Adaptive Optics from 26 Apr 2005 through 29 Apr 2005
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    Ground Layer Adaptive Optics
    from 26 Apr 2005 through 29 Apr 2005

Preliminary Program




Dear Workshop Participants,


For the discussion on Wednesday afternoon, we would like you to think about topics to bring into the discussion, such as: a new problem, a new invention, something that either other people or you could benefit by. Topics will, not exclusively, include the following:

  • Importance of site & turbulence characterization to GLAO
  • Limitations of the technique
  • Value of GLAO to the astronomical community
  • Experimental verification of the concepts


Thank you!

The organizers


Tuesday April 26


12:30-13:00 Registration and Coffee


13:00-13.05 Martje Kruk: Welcome to the Lorentz Center


13:05-13:15 Andreas Quirrenbach: Leiden Observatory Welcome


13:10-13:40 Remko Stuik: GLAO and workshop Introduction


Session 1 GLAO Projects


13:40-14:15 Rene Rutten

GLAS A Raleigh laser guide star system for the WHT



14:15-14:50 Roger Angel



15:00-15:15 Coffee break


15:15-15:50 Richard Myers

Gemini GLAO (30+5)


15:50-16:25 Norbert Hubin

GLAO Projects and status at ESO (30+5)


16:25-17:00 Stefan Strbele

Muse AO (30+5)


17:00-17:30 Topical Discussion

(GLAO challenges in current systems)


17:30 Wine and Cheese party at the Lorentz Center


Wednesday April 27



09:00-09:30 Coffee


Session 2 GLAO WFS concepts


09:30-10:20 Magalie Nicolle

Multi-object WFS concepts VLT/ELT GLAO (30+10)


10:20-11:00 Michael Lloyd-Hart

Multi-LGS wavefront sensing at MMT- (30+10)


11:00-11:45 Topical Discussion

(GLAO WFS concepts)


11:45-13:00 Lunch


Session 3 GLAO modeling


13:00-13:40 Jeff Stoesz

GLAO analytical modeling tool (30+10)


13:40-14:20 Miska le Louarn

Ground Layer AO simulations at ESO (30+10)


14:20-14:50 Carmelo Arcidiacon

GLAO from 10m to 100m (25+5)


14:50-15:20 Topical discussions

GLAO Modeling


15:20-15:30 Coffee


15:30-17:00 General Discussion


18:00 Guided Tour followed by Conference Dinner

at Hooglandse Huys, Leiden


Thursday April 28



09:00-09:30 Coffee


09:30-10:00 Wrap-up of the general discussion


Session 4 GLAO Experiments and verification


10:00-10:40 Tim Morris

WHT RLGS (30+10)


10:40-11:20 Richard Wilson

SLODAR profiling of ground-layer turbulence (30+10)


11:20-12:00 Sebastian Egner

MANU-CHAO: A Ground-Layer Adaptive Optics Experiment

for the TNG



12:15-13:15 Lunch at Hotel het Witte Huis



13:15-13:55 Christoph Keller

Solar AO as a test bed for GLAO en MCAO (30+10)


13:55-14:35 Fernando Quirros-Pacheco

Control for GLAXO: experimentel verification with MAD



14:35-15:30 Topical Discussion

GLAO concept Verification


15:30 Summary & Closing of Workshop & Coffee


16:00-17:30 GLAO mini hands-on (GL)AO simulation workshop


20:00-21:00 Oort Lecture - Prof. Anneila Sargent

New Worlds from Dust and Grains (limited tickets available)




Discussion items:

Laurent Jolissaint

WFAO with 2 DMs

Prediction of WFAO system performance, based, beside others, on recent studies for Gemini South observatory, are not necessarily as good as one might have expected. What can be done for boosting a little bit the performances? Well, the advantage of WFAO is the size of the corrected field. Now, what if we keep the large field, i.e. NGS and/or LGS spreaded in a a few arcminutes, but we add a second DM at an optimal altitude, driven by the tomographic informatins already available from the WF sensing? In a few slides, I present the results of a system with perfect knowledge of the tomographic information in a large (~5-10') field - because I would like to see what is the upper boundary of the system's performances - with 2 DM optimally conjugated, and compare it with the best WFAO 1DM case.


Jeffrey A. Stoesz

Currently GLAO feasibility studies use a zoo of Cn2 profiles (as I call them) each with an associated probability. These zoos are a crude statistical description of real profile measurements. What are some alternative statistical descriptions of real profile data that can be easily turned into AO simulation input? Would it be useful to define different statistical descriptions, suited to classical AO, GLAO, and MCAO simulations?






Title:The Gemini Ground Layer Adaptive Optics Feasibility Study

Author: Richard Myers


Durham University UK

HIA, NRC, Canada

University of Arizona, USA


A GLAO feasibility study has been conducted for the Gemini Observatory by three institutions, which reported in March 2005. The subject was the implementation of GLAO on one of the Gemini 8-m telescopes.

Our study comprised a science workshop which led to science, functional and performance requirements definition, analytical modelling to explore the system trades, development of design concepts, Monte Carlo modelling of the baseline concept for performance evaluation, and preliminary planning and costing of implementation. We summarise all these aspects and describe the baseline implementation concept, which is an adaptive secondary mirror with four sodium laser guide stars and three natural guide stars.



Title: Ground layer AO simulations at ESO

Authors: M. Le Louarn, Ch. Verinaud, V. Korkiakoski and N. Hubin


In this talk, we will present the GLAO simulations made at ESO, for three different projects. The second generation VLT instruments MUSE and Hawk-I are planned with GLAO correction, both with multiple laser guide stars. We have made a parametric analysis of the parameters affecting the performance of both systems, and will present the results.

In second part of this talk, we will present work done in the framework of extremely large telescopes. We will show simulation results for telescope diameters of up to 100m, with the particularity that the GLAO reference sources are natural guide stars. The sky coverage and performance as a function of various parameters will also be investigated.



Title:SLODAR profiling of ground-layer turbulence

Author: Richard Wilson


Preliminary data on ground-layer turbulence from the Durham/ESO SLODAR turbulence profiler will be presented. SLODAR is a triangulation technique in which the turbulence altitude profile is recovered from a cross-correlation of Shack-Hartmann wavefront sensor data for bright double stars. The prototype portable SLODAR system, which was commissioned by ESO and built by the Center for Advanced Instrumentation (CfAI) at Durham, is optimised for profiling of turbulence in the first kilometer above the observing site. The instrument was installed at Cerro Paranal in January 2005, following a short campaign at Cerro Tololo for inter-comparison with MASS-DIMM and SODAR (accoustic turbulence ranging) instruments.



Title: MANU-CHAO: Recent progress in the GLAO experiment for the TNG

Authors: S. Egner, R. Ragazzoni, W. Gaessler, J. Farinato, E. Diolaiti, C. Arcidiacono, E. Vernet-Viard


MANU-CHAO is a Ground-Layer Adaptive Optics Experiment for the TNG (Telescopio Nazionale Galileo) on La Palma. It was developed and built at the Instituto Astroficia di Arcetri and will use up to four natural guide stars. The system optically co-adds the pupils of four pyramid wavefront sensors onto one detector.

We will present the system and show some recent results of tests with fixed phase screens evaluating some characteristics of a GLAO system. Plans for upcoming tests with moving phase screens are presented as well. The required hardware (Atmosphere and Telescope simulator, Deformable mirror) and software does already exist at the MPIA in Heidelberg. As an outlook I will present how MANU-CHAO can be integrated into the already existing AO system at the TNG (AdOpt@TNG) and the possibility of an on-sky test.



Title: Solar AO as a test bed for GLAO and MCAO

Authors: Christoph U. Keller, National Solar Observatory, Tucson, USA


The convective pattern on the solar surface provides natural guiding structures over a field of view of 0.5 degrees. Combined with the strong ground-layer seeing that occurs in most locations during the day, the Sun provides a unique testbed for ground-layer adaptive optics (GLAO) and multi-conjugate adaptive (MCAO) optics. Indeed, the successful tests of MCAO concepts have already been carried out at solar telescopes. I will provide a brief overview of solar adaptive optics, discuss the main differences to night-time adaptive optics systems, and identify ways to test MCAO and GLAO concepts using solar telescopes.


Title: Ground layer correction for large and extremely large telescopes: performance of multi-object wave-front sensing concepts

Authors: Nicolle, M., Fusco, T., Muchau, V., Rousset, G., Blanc, A. and Beuzit, J.-L.

Keywords : adaptive optics, ground layer, wave-front sensing, extremely large telescopes.


Adaptive optics (AO) enable large telescopes to provide almost diffaction limited

images. Unfortunately the AO corrected field is limited by the angular correlation of the turbulent wave-fronts. However many scientific goals require a wide and uniformly corrected field, even with a partial correction. Ground Layer Adaptive Optics systems are supposed to provide such a correction by compensating the lower part of the atmosphere only. Indeed this part of the atmosphere is in the same time highly turbulent and isoplanatic on a rather wide field. In such a system the wave-front analysis is a major bet. Measuring the ground layer turbulence requires multi-object wave-front analysis. Two multi-object wave-front sensing concepts have been proposed so far. Here are presented the results of a study on the performance of both concepts. This study is based on an analytical modeling of the wave-front measurement in both cases. A criterion for the estimation of both concepts performance have been proposed. First results on the behaviour one can expect from one concept or the other have been given in a previous presentation.

For a start we present here results obtained by improving the analytical model. Nevertheless this model is based on simplified hypothesis and do not account for many of the limitations of AO correction. Therefore a numerical model has been implemented in order to complete the results of the analytical one. A confrontation of both models is presented, leading to a study of advantages and drawbacks of both wave-front sensing concepts. In particular, an application to very large and extremely large telescopes is developed.

january 26, 2005