GLAO WorkshopGLAO WorkshopLeiden 26-28 April 2005Leiden 26-28 April 2005

Remko Stuik

Leiden Observatory

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Outline of the talk/workshopOutline of the talk/workshop

• Introduction

• GLAO Projects

• GLAO Wavefront Sensing concepts

• GLAO Modeling

• GLAO Experiments and Verification

• Conclusions

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GoalGoal

• From the workshop proposal“The aim of the workshop is to connect people from various groups working on GLAO-related projects. We hope to evolve a better appreciation of the various GLAO methods proposed, as well as arrive at concrete solutions to some of the particular problems. At the end of the workshop, we hope that we will have clearer guide lines for the implementation of current and future GLAO projects.”

• Talks

• Discussion blocks

• General Discussion

• Social events

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What is GLAO?What is GLAO?

Lower SR Higher SR

On-axis‘Classical’ AO Extreme AO

Wide Field

GLAO MCAO

• Only correction of the ground layer• Moderate correction• Large Field of View (>> MCAO)

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What do you need for GLAO?What do you need for GLAO?

• Some guide stars– Wavefront sensor scheme

• Modeling– Atmospheric input– Comparison with ‘real life’

• GLAO reconstruction algorithm– How to separate the ground layer?

• Experimental Verification• Collaborating atmosphere

– Distribution of the turbulence?– Go to Antarctica?

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What is your turbulence profile?What is your turbulence profile?• Many measurement campaigns

– What accuracy is required?– Influence of variability on GLAO performance?

Slodar profiling by R. Wilson

La Palma

Paranal

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How to sense your wavefront?How to sense your wavefront?

• Separation of– Low altitude– High altitude

• Multiple NGS

• LGS + NGS

• Multiple LGS

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What is needed for modeling and reconstruction?What is needed for modeling and reconstruction?

• The right tools– Development of GLAO algorithms

• Virtual tomography?– Closed loop correction terms?

• Optimal Cn2 weighting?

• Layer Oriented?

• How to use the WFS data?– The art of ignoring information

• The right information– Statistical versus real atmosphere– Variations in the atmosphere

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Virtual Tomography in closed loopVirtual Tomography in closed loop

Real DM

LGS

Virtual layer

Virtual tomography idea:1. Multi-layer tomography (“mcao”)

2. Projection: Virtual Real

Closed loop: need correction term to WFS before tomographic reconstruction.

Problem:In closed loop, WFSs don’t see thevirtual layer at the conjugate altitudewhere it was calibrated.

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In practice…In practice…

• Simple example: 1 real DM + 1 virtual DM

WFS1

WFS2

WFS3

DM1 VDM

{ G0 , G1 } = G system matrix

calibration: s = Gc0

where c0 = [cT , vT ]T

CL correction: = (G0T – G1)v

s = s + tomography: c0 = Es

projection: c = c + Tv(E = wavefront estimator, T = modal transformation/optional)

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What can already be verified?What can already be verified?

• Wavefront sensing schemes– Different projects already running

• Turbulence characterization

• Modeling– Check performance operational AO systems

• Comparison with solar AO See also talks in this Workshop

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The ProgramThe ProgramTuesday April 2613:00-13:40 Introduction13:40-17:30 GLAO Projects17:30-19:00 Wine and Cheese Party

Wednesday April 2709:30-11:45 GLAO WFS Concepts11:45-13:00 Lunch at Gorlaeus Cantina13:00-17:00 GLAO Modeling17:30-19:00 Workshop Diner

Thursday April 2809:30-12:15 Experimental Verification I12:15-13:15 Lunch at the Witte Huis13:00-17:30 Experimental Verification II20:00-21:00 Oort Lecture (Tickets!)

• There will be NO proceedings • There will be a summary of discussions• I will collect presentations for the web site

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Social ProgramSocial Program• Wine and Cheese Party

– Tuesday at the Lorentz Center• Workshop Dinner

– Wednesday at Hooglandse Huys• Dinner + guided tour in old Dutch church

• Lunch at the Witte Huis– Thursday, 10 minutes walking

• Oort Lecture by Prof. Anneila Sargent (Caltech) “New Worlds from Dust and Grains”

– At the ‘Groot Auditorium’ of the University Leiden (city center) – tickets required• Outside the workshop

– Queensday• Amsterdam—29 april, 19:00-late, 30 april• Den Hague—KoninginneNach 29 April, 19:00-late

– Flowers• Keukenhof• Cycling in the area

• Getting there and back– Bike!

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Bikes are ideal for transport…Bikes are ideal for transport…

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Although the weather isn’t always nice…Although the weather isn’t always nice…

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And be careful what you take with you!And be careful what you take with you!

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Any questions?Any questions?

?