Laser Guide Star Adaptive Optics for Astronomy

359 Pages·2000·12.91 MB·English

by  J. C. Dainty (auth.)

Laser Guide Star Adaptive Optics tor Astronomy
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Series C: Mathematical and Physical Sciences - Vol. 551
Laser Guide Star Adaptive Optics
for Astronomy
edited by
N. Ageorges
European Southern Observatory,
Santiago, Chile
and
c.
Dainty
Imperial College,
Blackett Laboratory,
London, United Kingdom
Springer-Science+Business Media, B.Y.
Proceedings of the NATO Advanced Study Institute on
Laser Guide Star Adaptive Optics for Astronomy
Cargese, France
September 29-0ctober 10, 1997
A C.I.P. Catalogue record for this book is available from the Library of Congress.
ISBN 978-90-481-5492-0 ISBN 978-94-015-9624-4 (eBook)
DOI 10.1007/978-94-015-9624-4
Printed on acid-free paper
All Rights Reserved
© Springer Science+Business Media Dordrecht 2000
Origina11y published by Kluwer Academic Publishers in 2000.
Softcover reprint of the hardcover 1s t edition 2000
No part of the material protected by this copyright notice may be reproduced or utilized in
any form or by any means, electronic or mechanical, including photocopying, recording or
by any information storage and retrieval system, without written permission from the
copyright owner.
TADLE OF CONTENTS
Preface ........................................................... xiii
List of Participants .................................................. xv
Chapter 1
OPTICAL EFFECTS OF ATMOSPHERIC TURBULENCE
J.e. Dainty
1 A Primer on Statistics and Random Processes 1
2 Kolmogorov Turbulence 3
3 Field Correlation and Phase Structure Function 4
4 Strehl Ratio, Marechal Criterion 7
5 Zemike Expansion of Kolmogorov Turbulence 8
6 Angle-of-Arrival Statistics 13
7 Long-and Short-Exposure Transfer Functions 15
8 Temporal Behaviour of Atmospheric Turbulence 17
9 Angular Anisoplanatism 19
10 Conclusion 21
Chapter 2
ADAPTIVE OPTICS WITH LASER GUIDE STARS: BASIC CONCEPTS
AND LIMITATIONS ................................................. 23
A. Quirrenbach
1 Introduction 23
2 The Formation of Artificial Guide Stars 24
3 The Tilt Determination Problem 25
4 Focal Anisoplanatism 30
5 Properties of the Sodium Atom and Sodium Layer 32
6 Sodium Guide Star Brightness 35
7 Laser Technology for Sodium Guide Stars 37
8 Practical Considerations 40
9 Laser Guide Star Experiments and Operational Systems 41
10 An Example: the ALFA System 43
11 Astronomy with Adaptive Optics and Laser Guide Stars 46
Chapter 3
THE PHYSICS OF THE somUM ATOM ................................ 51
E.J. Kibblewhite
I Introduction 51
2 Sodium in the Mesosphere 51
v
vi
3 All You Need to Know about Atomic Physics 52
4 Saturation ofthe Sodium Atom in the Radiation Field 55
5 Radiation Pressure 57
6 Optical Pumping 57
7 Calculation ofthe Return Flux from the Layer for a Single Frequency
Laser 60
8 Return Flux for Different Laser Spectral and Pulse Formats 62
9 Summary and Conclusions 65
Chapter4
THE DESIGN AND PERFORMANCE OF LASER SYSTEMS FOR
GENERATING somUM BEACONS ................................... 67
EcJward Kibblewhite
1 Introduction 67
2 How Small Can We Make the Laser Beacon? 67
3 Saturation Properties of the Laser at the Sodium Layer 73
4 Lasers for the Generation of Sodium Beacons 74
4.1 CW Dye Lasers -(UCIUAlMax Planck) 74
4.2 Pulsed Dye Lasers 75
4.3 Sum-Frequency Lasers 76
5 Laser Field Tests 81
5.1 Laser Beacon Profile at the Layer 81
5.2 Return Flux for the Sodium Beacon 83
5.3 Optical Pumping Effects 84
6 Estimation ofthe Beacon Position for the Gemini South Telescope 85
7 System Issues 87
Chapter 5
LASER GUIDE STAR OPERATIONAL ISSUES .......................... 89
c.E. Max
1 Introduction 89
2 Operational Implications for the Laser System 90
2.1 Rayleigh Scattering 90
2.2 Focus Changes 92
2.3 Variations in Sodium Column Density 93
2.4 Requirement to Nod the Telescope for Infra-Red Observing 93
3 Calibration of the Adaptive Optics System for Sodium Laser Guide
Star Operation 94
3.1 Types of Internal Calibration Sources 96
3.2 Static Calibration 96
3.3 Auxiliary Wavefront Sensors 97
3.4 Dynamic Calibration (Real-Time Point-Spread-Function
Measurements) 98
4 Safety Considerations Regarding Laser Guide Star Systems 99
Vll
4.1 Laser Eye Safety 100
4.2 Fire Safety 100
4.3 Aircraft Avoidance 101
4.4 Spacecraft Damage Avoidance 102
4.5 Laser Coordination on Multi-Telescope Summits 103
5 Conclusions 104
Chapter 6
THE CONE EFFECT ................................................ 107
R. Foy
1 Introduction 107
2 What is the Cone Effect? 108
3 Parameters and Astrophysical Implications 109
4 Multiple LGS: Stitching Method 112
5 Multiple LGSs: the 3D-Mapping Method 114
5.1 Hypotheses 115
5.2 Telescope to Laser Spot Array Approach 115
5.3 Laser Spot Array to Telescope Approach 118
5.4 The Inversion 119
5.5 Modal Approach 119
6 Spot Array Geometry and Field 119
7 Conclusion 122
Chapter 7
LASER GUIDE STAR ADV ANCED CONCEPTS: TILT PROBLEM ......... 125
Roberto Raggazoni
1 The Framework 125
2 Searching for New Ideas 126
3 Tuning the Parameters 128
4 Looking for Non-Standard Tiny Effects 129
5 LGSs in a New Perspective 134
5.1 A Statistical Approach 135
5.2 Gauging with a Natural Guide Star 138
6 A Few Remarks about Thinking Globally 142
7 Experimental Verifications 144
8 Future Directions 145
Chapter 8
THETILTPROBLEM-MULTIWAVELENGTH ......................... 147
R. Foy
1 Introduction: What is the Tilt Problem 147
2 Methods to Measure the Tilt 148
2.1 Use of a Natural Guide Star 148
2.2 The Dual Adaptive Optics Concept 150
3 Principle ofthe Polychromatic Artificial Star 151
viii
3.1 Required Photon Flux 153
3.2 Rayleigh and Raman Scattering 154
3.3 The Excitation ofthe 4P3/2 Energy Level ofMesospheric Sodium
Atoms 154
4 Excitation ofthe 4P3/2 Atomic Level of Sodium 155
4.1 The 3SI/2 -+ 4P3/2 Absorption 156
4.2 The 3SI/2 -+ 4Ds/2 : Non-Resonant Two-Photon Absorption 156
4.3 Saturations 157
4.4 Integration Time 158
4.5 Laser Power 159
5 From the Theory to the Experiments: PASS 159
5.1 Description of the PASS Experiment 160
5.2 Results and Discussion 160
5.3 The Power Balance between the Two Beams 163
6 From the Experiment to a Full Demonstration: ELP-OA 163
6.1 Atomic Physics 164
6.2 Lasers 164
6.3 Optics 164
6.4 Infrastructure 165
6.5 Integration 165
6.6 Measurements and Analysis 166
7 Conclusion 166
Chapter 9
SKY COVERAGE WITH LASER GUIDE STAR SYSTEMS ON
8m TELEScOPES .................................................. 169
M Le Louarn
1 Introduction 169
2 Sky Coverage Computation 170
2.1 AO System Model 170
2.2 Statistical Sky Coverage 175
2.3 Sky Coverage: Object-Counts 177
3 Conclusion 182
Chapter 10
GROUND BASED ASTRONOMY WITH ADAPTIVE OPTICS ............. 185
Stephen T. Ridgway
1 Introduction 185
2 The Investment in Adaptive Optics 185
3 Does Adaptive Optics Work? 186
4 Where Are the Adaptive Optics Systems 188
5 What Will Adaptive Optics 00 for Astronomy? 188
6 Sensitivity and Speed of Observations with Adaptive Optics 189
6.1 Raw Sensitivity 189
6.2 Multiobject Observations 192
ix
7 The Isoplanatie Pateh 192
8 The Point Spread Funetion 192
9 What about Photometry? 193
10 Coronography, Nulling, Super AO and Speekle 194
11 Adaptive Opties and Speetroseopy 196
12 How Adaptive Opties Will Make the Rieh Rieher 196
13 How Mueh is Adaptive Opties Used 197
14 What Does Natural Guide Star Adaptive Opties Offer Astronomers? 197
14.1 Correetion of Statie Aberrations 198
14.2 Painless Foeus 198
14.3 Tilt Correetion 199
14.4 Resolution Irnprovement near Suffieiently Bright Stars 200
15 Why Not Higher Order Correetion? 200
16 Laser Beaeons 200
17 Partial Adaptive Correetion 202
18 Seienee Results from Adaptive Opties 203
19 A Closer Look at Adaptive Opties Scienee 204
19.1 Young Stars 205
19.2 Solar System 206
19.3 Extragalaetie and Galaetie Center 207
19.4 Binary Stars and Star Clusters 208
19.5 Compaet Nebulae and Cireurnstellar Shells 209
19.6 Summary of Scienee Direetions 210
20 Future Direetions in Adaptive Optics 210
20.1 Natural Guide Star Adaptive Opties 211
20.2 Sodiurn Beaeon Adaptive Opties 211
20.3 Rayleigh Beaeon Adaptive Opties 211
20.4 Adaptive Optics for Partial Correetion 212
20.5 Low Altitude Turbulenee 212
20.6 Adaptive Secondaries 213
21 Summary 213
Chapter 11
POLARIMETRIC MEASUREMENTS AND DECONVOLUTION
TECHNIQUES ..................................................... 219
N. Ageorges
1 Introduetion 219
2 Polarimetrie Measurements 219
2.1 Introduetion 219
2.2 Observational Mode 220
2.3 How to Calibrate the Data 221
2.4 Analysis of the Data 222
2.5 Results and Conclusion 228
3 Post-Proeessing of Adaptive Opties Data: Reeovery ofDiffraetion
Limited Images 230
x
3.1 Introduction: Why Are Deconvolution Techniques Needed? 230
3.2 What Does Exist? 230
3.3 Why Is It Different for Adaptive Optics? 236
3.4 New Methods WeIl Adapted to Adaptive Optics Data 236
Chapter 12
MEASURING ASTEROIDS WITH ADAPTIVE OPTICS .................. 243
Jack D. Drummond
1 Introduction 243
2 Ellipses from a Triaxial Ellipsoid 246
2.1 Basic Formulae 246
2.2 Useful Relationships 247
3 Fitting the Ellipse 250
3.1 A Mean Ellipse 250
3.2 The Fourier Domain 251
4 A Triaxial Ellipsoid from Ellipses 254
4.1 Residuals for Least Squares Fitting 254
4.2 Derivatives for Least Squares Fitting 256
4.3 Final Calculations 257
5 Summary 259
Chapter 13
THE ENVIRONMENTS OF YOUNG STARS ............................ 263
T.P. Ray
1 Introduction 263
2 The Early Years 263
3 The T Tauri and Herbig AelBe Stars 268
4 HH Flows from Young Stars 271
5 Disks around YSOs 277
6 A Few Examples ofHow AO Could Help Our Understanding ofYSOs 279
Chapter 14
DISTANT (RADIO) GALAXIES: PROBES OF GALAXY FORMATION ..... 285
Huub Rottgering
1 Introduction 285
2 Lookback Time and Redshift 286
3 Main Questions 288
3.1 Galaxy Evolution and Formation 288
3.2 Active Galactic Nuclei: Quasars, Radio Galaxies 288
4 Normal Galaxies at z - 3 290
4.1 Models of Galaxy Formation 290
5 Distant Radio Galaxies 293
5.1 Cygnus A 295
5.2 Search for High Redshift Radio Galaxies 297
5.3 Properties ofHigh-z Radio Galaxies 298