Multi-Band IR Sensor for Earth Observation
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http://lib.uliege.be https://matheo.uliege.be Master thesis : Multi-band IR sensor for Earth Observation Auteur : Vilaboa Perez, Jesus Promoteur(s) : Habraken, Serge Faculté : Faculté des Sciences appliquées Diplôme : Master en ingénieur civil en aérospatiale, à finalité spécialisée en "aerospace engineering" Année académique : 2018-2019 URI/URL : http://hdl.handle.net/2268.2/6781 Avertissement à l'attention des usagers : Tous les documents placés en accès ouvert sur le site le site MatheO sont protégés par le droit d'auteur. Conformément aux principes énoncés par la "Budapest Open Access Initiative"(BOAI, 2002), l'utilisateur du site peut lire, télécharger, copier, transmettre, imprimer, chercher ou faire un lien vers le texte intégral de ces documents, les disséquer pour les indexer, s'en servir de données pour un logiciel, ou s'en servir à toute autre fin légale (ou prévue par la réglementation relative au droit d'auteur). 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University of Li`ege- Faculty of Applied Sciences Multi-band Infrared Sensor For Earth Observation Author: Jes´usVilaboa P´erez Academic advisor: Prof. Serge Habraken Assistant: Victor Laborde Graduation Studies conducted for obtaining the Master's degree in Aerospace Engineering Academic year 2018-2019 Abstract A new CubeSat is in development by students and professors of the Univer- sity of Li`egeand the Centre Spatial de Li`ege.The CubeSat OUFTI-NEXT will measure the hydric stress in crop fields in order to enhance the man- agement efficiency of the water resources for agriculture. This CubeSat incorporates a thermal imager to capture the electromagnetic radiation of the infrared band. In this project, it is analysed the performance of the different infrared detectors that can be used within the CubeSat optical instrument. There are a few examples of CubeSat missions observing in the Mid-Wave Infrared Band or in the Long-Wave Infrared band. However, any of these missions can observe in both bands at the same time. This Master Thesis describes the feasibility of an optical instrument for a CubeSat observ- ing in both bands with the use of a single detector. With this aim, the performance of the two main groups of infrared detectors, photodetectors and thermal detectors, is measured in terms of temperature resolution and signal-to-noise ratio in the space environment. These computations are carried on with the model of equations developed in this Master Thesis. Keywords: CubeSat, Dual-band, Microbolometer, Photodetector, NETD, SNR. Jes´usVilaboa P´erez June 2019 Acknowledgements I would like to express my gratitude to Prof. Serge Habraken for the astounding opportunity to possibly realise my Master Thesis in the Centre Spatial de Li´ege.I really appreciate all the help and advice received from him during the whole project. I can state that I have found a field in space engineering that extremely enthusiasm me and in which I would like to continue in the near future. I am also very grateful for all the advice received from Victor Laborde that always helped me to continue when the complexity of the project was very high. My special thanks to Prof. Jer^ome Loicq for its support and help to coordinate the work of Antonio and mine to advance further in this project. Thanks also to Prof. Ga¨etanKerschen since he presented my the OUFTI project and the opportunity to do a Master Thesis in the topic. Thanks to the other students involved in the project, Antonio, Arnau, Alex and Ysaline. And finally, I am very grateful to my family and friends who always support me. Contents 1 Introduction to the project 1 1.1 The OUFTI CubeSat mission . .1 1.2 Differences between the Mid-Wave Infrared and the Long-Wave Infrared bands . .2 1.3 Objectives of the project . .3 2 Infrared optical instruments 4 2.1 Introduction . .4 2.2 Infrared optics . .4 2.3 Infrared detectors . .6 2.3.1 Two main types of detectors . .7 2.3.2 Historical background of infrared detectors . .7 2.4 Figures of merit of infrared detectors . 10 2.4.1 Responsivity . 10 2.4.2 Spectral range. Cut-off wavelength . 12 2.4.3 Quantum efficiency . 13 2.4.4 Detectivities . 14 2.4.5 Response time . 15 2.5 State of the art of photodetectors and thermal detectors. Space appli- cations. 17 2.5.1 Photodetectors . 17 2.5.2 Thermal detectors . 36 2.6 Second comparison of photodetectors and thermal detectors . 44 2.7 Conclusions . 46 i CONTENTS 3 Multiband operation 48 3.1 Introduction to multiband detectors . 48 3.1.1 Types of multiband detectors . 48 3.1.2 Dual-band microbolometers . 53 3.2 Devices to split the light into its wavelengths . 54 3.2.1 Introduction . 54 3.2.2 Optical filters and multispectral imaging systems . 54 3.3 Conclusions . 66 4 Working principle of infrared detectors 68 4.1 Introduction . 68 4.2 Types of focal plane arrays . 68 4.3 The read-out process . 69 4.3.1 Photodetectors . 70 4.3.2 CCD and CMOS architectures for thermal detectors . 75 4.4 Characteristics times of infrared detectors . 76 4.4.1 Integration time of the satellite . 77 4.4.2 Exposure time of the detector . 78 4.4.3 Response time of the detector . 78 4.4.4 Integration time of the read-out circuit (ROIC) . 79 4.4.5 Time for the reading-out of the charge . 80 4.4.6 Idling/clearing of the detector . 81 4.4.7 Frame rate of the detector . 81 4.4.8 Controlling the exposure times . 82 4.4.9 Response time solution for microbolometers thermal detectors. Time delay integration . 84 4.4.10 Conclusions . 87 5 Temperature resolution and Signal-to-noise ratio of infrared detec- tors 88 5.1 Introduction . 88 5.2 Noise description in infrared photodetectors . 89 5.2.1 Shot noise and Generation-Recombination noise . 89 5.2.2 Dark current . 91 5.2.3 Thermal noise or Johnson noise . 91 ii CONTENTS 5.2.4 Flicker noise 1/f . 92 5.2.5 Pattern noise . 93 5.2.6 Shot noise, Johnson noise and 1/f noise variation with the fre- quency bandwidth . 93 5.2.7 Noise contributions in a photodetector . 94 5.3 Different noises in thermal detectors . 94 5.3.1 Flicker noise 1/f . 95 5.3.2 Thermal noise or Johnson noise . 95 5.3.3 Temperature noise and radiative thermal exchange noise . 96 5.3.4 Read-out noise . 96 5.3.5 Noise contributions in thermal detectors . 96 5.3.6 Noise model of bolometer uncooled thermal detectors . 97 5.3.7 Cooling down a microbolometer . 98 5.4 Noise figures of merit . 99 5.4.1 Noise Equivalent Power (NEP) . 99 5.4.2 Specific Detectivity, D∗ ....................... 101 5.4.3 Minimum Resolvable Temperature Difference (MRTD) . 102 5.5 Temperature resolution. Noise Equivalent Temperature Difference (NETD)103 5.5.1 NETD measurement in ground . 104 5.5.2 Noise Equivalent Temperature Difference, NETD, theoretical model . 106 5.5.3 NETD measurement in space . 110 5.5.4 NETD for different optical instruments . 112 5.6 Signal-to-noise ratio (SNR) . 112 5.6.1 SNR in space . 115 5.6.2 Specific detectivity . 116 5.7 Conclusions . 118 6 CubeSat and satellite missions in the infrared 120 6.1 Introduction . 120 6.2 CubeSat missions . 120 6.3 Satellite missions . 123 6.4 Conclusions . 123 iii CONTENTS 7 Results and analysis of the different detectors offered by the manu- facturers 126 7.1 Temperature resolution requisites for the mission . 126 7.1.1 Differences between the MWIR and the LWIR band . 128 7.2 Single-band detectors . 128 7.2.1 Single-band MWIR detectors . 128 7.2.2 Single-band LWIR detectors . 133 7.3 Multi-band detectors . 136 7.3.1 Multi-band photodetectors . 136 7.3.2 Multi-band microbolometers . 138 8 Conclusions and future perspective 144 A Performance of the different detectors for the infrared 149 Bibliography 164 iv List of Figures 2.1 Definition of angular resolution. [1] . .6 2.2 Roadmap of the major milestones in development of detectors for the infrared. [2] . .9 2.3 Responsivity vs. wavelength for photodetectors and thermal detectors in the infrared. [2] . 12 2.4 Quantum efficiency vs. wavelength for the main categories of photode- tectors. [3] . 13 2.5 Differences bettween the exponential response time function of thermal detectors and the step response time function of photodetector. 16 2.6 Representation of the valence band and the conduction band of a p-n semiconductor. [4] . 19 2.7 InSb 'Pelican D 640' photodetector from SCD. 640x512 pixels, 15µm pixel pitch for the 3.6 µm to 4.9 µm infrared range. [5] . 21 2.8 Comparison of the specific detectivity in function of the wavelength for QDIP, HgCdTe and T2SL photodetectors at a)high temperatures and b)low temperatures.[6] . 27 2.9 Noise Equivalent Temperature Difference (NETD) vs. temperature of the FPA for different barrier detectors with cut-off wavelength a)5 µm and b) 10 µm.