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Disk-Resolved Photometry of Small Bodies

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Disk-Resolved Photometry of Small Bodies Disk-Resolved Photometry of Small Bodies Von der Fakultät für Elektrotechnik, Informationstechnik, Physik der Technischen Universität Carolo-Wilhelmina zu Braunschweig zur Erlangung des Grades einer Doktorin der Naturwissenschaften (Dr.rer.nat.) genehmigte Dissertation von Sofie Spjuth aus Ockelbo, Schweden Bibliografische Information Der Deutschen Bibliothek Die Deutsche Bibliothek verzeichnet diese Publikation in der Deutschen Nationalbibliografie; detaillierte bibliografische Daten sind im Internet über http://dnb.ddb.de abrufbar. 1. Referentin oder Referent: Prof. Dr. Karl-Heinz Glaßmeier 2. Referentin oder Referent: Prof. Dr. Marcello Fulchignoni eingereicht am: 7 May 2009 mündliche Prüfung (Disputation) am: 9 July 2009 ISBN 978-3-936586-98-5 Copernicus Publications 2009 http://publications.copernicus.org c Sofie Spjuth Printed in Germany Contents Summary 5 1 Introduction 9 1.1 Asteroids & Comets: an Overview . .9 1.1.1 History . .9 1.1.2 Origin . 10 1.1.3 Classification . 11 1.1.4 Optical Characteristics . 12 1.2 Motivation . 15 1.2.1 Aims and Overview of the Thesis . 16 1.3 Overview of Chapters . 19 2 Hapke’s Light Scattering Theory 21 2.1 Radiative Transfer . 22 2.2 Photometric Properties and Hapke Parameters . 22 2.2.1 Single Scattering Albedo . 24 2.2.2 Asymmetry Factor(s) . 26 2.2.3 Mean Roughness Slope Angle . 26 2.2.4 Opposition Parameters . 27 2.2.5 Effective Ranges . 33 2.3 Hapke’s Photometric Model . 33 2.3.1 Dark Surface . 33 2.3.2 Bright Surface . 36 2.3.2.1 Isotropic Multiple Scattering . 36 2.3.2.2 Anisotropic Multiple Scattering . 36 2.3.3 Shadow Hiding Opposition Effect . 38 2.3.4 Coherent Backscatter Opposition Effect . 38 2.3.5 Rough Surface . 38 2.3.6 Porosity . 41 2.4 Integrated Quantities . 41 2.4.1 Geometric albedo . 41 2.4.2 Bond albedo . 42 2.5 Other Light Scattering Models . 43 2.5.1 Lambert’s . 43 2.5.2 Minnaert’s . 43 2.5.3 Lommel-Seeliger’s . 43 3 Contents 2.5.4 Lunar-Lambert’s . 44 2.5.5 Lumme and Bowell’s . 44 2.5.6 Shkuratov . 45 2.5.7 Mishchenko . 45 2.5.8 Mie . 45 3 Photometric Properties from Disk-Resolved Images 47 3.1 Overview of the Method . 47 3.2 OASIS simulator . 51 3.2.1 Transformation of Coordinate Systems . 52 3.2.2 Geometry of Facets . 53 3.2.3 Facet Sorting . 54 3.3 Image Matching . 54 3.4 I=F Extraction . 55 3.5 Derivation of Hapke Parameters from Observations . 57 3.5.1 Minimization Method . 57 3.5.2 Error Analysis . 58 3.5.3 Local Variations . 58 3.6 Summary . 59 4 Validation of the Method 61 4.1 BDR Extraction . 61 4.2 Hapke Parameters Extraction . 63 4.2.1 Smooth Surface . 66 4.2.2 Rough Surface . 66 4.2.3 Shape Error . 69 4.3 Moon . 69 4.4 Albedos . 70 4.4.1 Geometric Albedo . 70 4.4.1.1 Spherical Shape . 73 4.4.1.2 Irregular Shape . 73 4.4.2 Bond Albedo . 74 4.4.2.1 Spherical Shape . 75 4.4.2.2 Irregular Shape . 75 4.5 Summary . 79 5 Disk-Resolved Photometry of Comet 9P/Tempel 1 81 5.1 Observations . 81 5.2 Input Parameters . 81 5.3 Results . 83 5.3.1 Spectral Reddening . 83 5.3.2 Global Hapke Parameters . 85 5.3.3 Local Variations . 89 5.3.4 Error Analysis . 95 5.4 Comparison with Previous Works . 97 5.5 Summary . 111 4 Contents 6 Disk-Resolved Photometry of Asteroid (2867) Steins with OSIRIS 113 6.1 Observations . 114 6.1.1 Calibration . 114 6.2 Input Parameters . 115 6.3 I=F Extraction . 117 6.4 Results . 118 6.4.1 Model Independent Quantities . 119 6.4.1.1 Geometric Albedo from Image . 119 6.4.1.2 Spectral Reddening . 120 6.4.2 Model Dependent Quantities . 120 6.4.2.1 Hapke Modeling . 120 6.4.2.2 Geometric and Bond Albedos from Hapke Parameters . 129 6.4.2.3 Comparison with Observation . 130 6.4.3 Local Variation . 132 6.4.4 Error Analysis . 132 6.4.5 Sample Comparison . 135 6.4.6 Hapke Modeling Including Porosity . 138 6.4.7 Other Photometric Models . 138 6.5 Discussion and Conclusion . 138 7 Investigation of Steins Flyby Scenarios 143 7.1 Motivation . 143 7.2 Geometry . 143 7.3 Trajectory Creation . 144 7.4 Science Output . 147 7.4.1 Radiators . 147 7.4.2 Longitude/Latitude Coverage . 147 7.4.3 Area Coverage . 148 7.4.4 Stereo Area Coverage . 149 7.5 Results . 149 7.5.1 Spherical Shape . 149 7.5.2 Irregular Shape . 151 7.6 Adopted Scenario . 152 7.7 Summary . 157 8 Outlook 159 A Coordinate Systems 161 A.1 Coordinate Systems . 161 A.1.1 NUC . 161 A.1.2 EQU . 161 A.1.3 VIS . 161 A.1.4 CCD . 161 A.2 Transformation of Systems . 162 A.2.1 NUC to EQU . 162 A.2.2 EQU to VIS . 162 5 Contents A.2.3 VIS to CCD . 163 B Hapke Parameters of Other Bodies 165 Bibliography 169 Publications 175 Acknowledgements 177 Curriculum Vitae 179 6 Summary The aim of any mission to small bodies is to better comprehend asteroids and cometary nuclei, key bodies for understanding the origin of the Solar System and for constraining the models of formation of the planets. Studying the photometric reflectance of small bodies can give insights into the physical properties of their surfaces and to allow identify different classes of.
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