Remote sensing of clouds with longwave infrared cameras at the Pierre Auger Observatory

Knowledge of atmospheric conditions at the site of a cosmic ray observatory is important, especially for measurements made using the fluorescence technique. At the Pierre Auger Observatory in Argentina, an extensive network of meteorological instruments is dedicated to atmospheric monitoring, several of which are used for the remote sensing of night-time clouds. Clouds can be identified passively by detection of the thermal radiation they emit, and are often strong radiators at long-wave infrared wavelengths. As part of the University of Adelaide’s contribution to the Observatory, we have in- stalled four infrared cameras at the Observatory for cloud detection. The current generation cloud cameras are radiometric, and are sensitive to the 8–14 μm waveband. However, identifying clouds is not necessarily straight- forward as atmospheric water vapour also absorbs and emits radiation at these wavelengths. In this dissertation, I present the method that I use to identify clouds in our thermal images. Another major focus of my studies has been to calibrate our cameras. However, as they were already collecting data at the Observatory, the routines had to be developed remotely. These methods have been reproducible for each of our cameras, and could perhaps benefit other researchers in this field.Thesis (Ph.D.) -- University of Adelaide, School of Physical Sciences, 201

Miniaturized Silicon Photodetectors

Silicon (Si) technologies provide an excellent platform for the design of microsystems where photonic and microelectronic functionalities are monolithically integrated on the same substrate. In recent years, a variety of passive and active Si photonic devices have been developed, and among them, photodetectors have attracted particular interest from the scientific community. Si photodiodes are typically designed to operate at visible wavelengths, but, unfortunately, their employment in the infrared (IR) range is limited due to the neglectable Si absorption over 1100 nm, even though the use of germanium (Ge) grown on Si has historically allowed operations to be extended up to 1550 nm. In recent years, significant progress has been achieved both by improving the performance of Si-based photodetectors in the visible range and by extending their operation to infrared wavelengths. Near-infrared (NIR) SiGe photodetectors have been demonstrated to have a “zero change” CMOS process flow, while the investigation of new effects and structures has shown that an all-Si approach could be a viable option to construct devices comparable with Ge technology. In addition, the capability to integrate new emerging 2D and 3D materials with Si, together with the capability of manufacturing devices at the nanometric scale, has led to the development of new device families with unexpected performance. Accordingly, this Special Issue of Micromachines seeks to showcase research papers, short communications, and review articles that show the most recent advances in the field of silicon photodetectors and their respective applications

Modelling and Design Optimisations of CMOS MEMS Single Membrane Thermopile Detector Arrays

Thermal imaging devices based on Complementary Metal-Oxide-Semiconductor (CMOS) and Micro-Electro-Mechanical System (MEMS) technology are widely used across consumer and industrial applications. The combination of CMOS and MEMS technologies allows for the production of devices with high performance, good reliability and consistent reproducibility. Additionally, these technologies allow devices to be manufactured at low cost and a high volume. There are several types of thermal sensing technologies, however, this thesis mainly focuses on 8×8 thermopile based Focal Plane Arrays (FPAs). The core principles governing the function of thermopiles are based on the Seebeck effect. In this thesis, the structure and fabrication process of thermopile FPAs are described and discussed. The thesis describes the functionality of the array chip and introduces a new experimental technique, called the bi-directional electrical biasing method, which was applied to obtain the device’s responsivity and crosstalk measurements. Compared to traditional measurement approaches using laser sources, this novel method significantly reduces the complexity of the experimental setup, as no external laser source is required. The crosstalk of the 8×8 array is ~2.69% and the responsivity is ~73.1 V/W. A detecting system using a larger array chip was designed, created and successfully applied in a series of experiments that involved gesture recognition and people counting. In order to enhance the performance of the current array device, a 3D simulation model based on the Finite Element Method (FEM) was built using the COMSOL Multiphysics simulation tool. The numerical model was validated by comparing the model’s simulated values for responsivity, crosstalk and temperature distribution with experimental results. The difference between the simulations and experimental results was 90 V/W in the model with tungsten tracks. A 32×32 array design demonstrates the smallest pixel size that can be achieved based on this thermopile array design. The 32×32 array design increased responsivity to ~77.18 V/W and crosstalk remained 6% when the pixel size was reduced further in a 64×64 array design, at this level of crosstalk, image quality is likely to be significantly affected. Future work may focus on the implementation of carbon nanotubes or novel 3D thermopile designs. Carbon nanotubes, when deposited over the array chip, could enhance the absorption of IR radiation. While new thermopiles employing a 3D design could dramatically reduce array size and potentially achieve a fill factor of 100%

Advanced CMOS Integrated Circuit Design and Application

The recent development of various application systems and platforms, such as 5G, B5G, 6G, and IoT, is based on the advancement of CMOS integrated circuit (IC) technology that enables them to implement high-performance chipsets. In addition to development in the traditional fields of analog and digital integrated circuits, the development of CMOS IC design and application in high-power and high-frequency operations, which was previously thought to be possible only with compound semiconductor technology, is a core technology that drives rapid industrial development. This book aims to highlight advances in all aspects of CMOS integrated circuit design and applications without discriminating between different operating frequencies, output powers, and the analog/digital domains. Specific topics in the book include: Next-generation CMOS circuit design and application; CMOS RF/microwave/millimeter-wave/terahertz-wave integrated circuits and systems; CMOS integrated circuits specially used for wireless or wired systems and applications such as converters, sensors, interfaces, frequency synthesizers/generators/rectifiers, and so on; Algorithm and signal-processing methods to improve the performance of CMOS circuits and systems

Photodetectors

In this book some recent advances in development of photodetectors and photodetection systems for specific applications are included. In the first section of the book nine different types of photodetectors and their characteristics are presented. Next, some theoretical aspects and simulations are discussed. The last eight chapters are devoted to the development of photodetection systems for imaging, particle size analysis, transfers of time, measurement of vibrations, magnetic field, polarization of light, and particle energy. The book is addressed to students, engineers, and researchers working in the field of photonics and advanced technologies

Passive terahertz imaging with lumped element kinetic inductance detectors

Progress towards large format, background limited detector arrays in and around the terahertz or sub-millimetre region of the electromagnetic spectrum has – until recently – been hampered by the complexities in fabrication and cryogenic electronic readout associated with increasing pixel counts. Kinetic inductance detectors or KIDs are a superconducting pair breaking detector technology designed to overcome these complexities. Traditionally, KID arrays have been developed for imaging in astronomy. However, the high sensitivities, broadband responses, fast time constants and high detector counts that are achievable – along with the simplicity of fabrication and readout compared to other contemporary technologies – make them suitable (and in fact desirable) for a variety of applications. This thesis documents the development of a concept instrument to demonstrate KID technology for general purpose imaging applications. Specifically, I present the design, construction and performance of a near background limited, quasi-video rate, passive imaging system based on arrays of Aluminium lumped-element KIDs. The camera operates in two atmospheric windows at 150 GHz (2 mm) and 350GHz (850 μm) with 60 and 152 pixels, respectively. Array fabrication was achieved with a single photolithographic cycle of thin film deposition, patterning and etching. Full array readout is with a single cryogenic amplifier and room temperature FPGA based frequency domain multiplexing electronics. The camera is the first of its kind in applying KID arrays to imaging systems outside of pure astrophysics research and is the result of efforts from the staff and students of the Astronomy Instrumentation Group (AIG) in the School of Physics and Astronomy with support from QMC Instruments Ltd. The system exemplifies the AIG’s world-leading expertise in the development of far-infrared/sub-mm instrumentation as well as QMCI’s vision to provide the highest quality terahertz optical components and detector systems to the global marketplace

Remote sensing data handbook

A digest of information on remote sensor data systems is given. It includes characteristics of spaceborne sensors and the supportive systems immediately associated therewith. It also includes end-to-end systems information that will assist the user in appraising total data system impact produced by a sensor. The objective is to provide a tool for anticipating the complexity of systems and potential data system problems as new user needs are generated. Materials in this handbook span sensor systems from the present to those planned for use in the 1990's. Sensor systems on all planned missions are presented in digest form, condensed from data as available at the time of compilation. Projections are made of anticipated systems

Earth imaging with microsatellites: An investigation, design, implementation and in-orbit demonstration of electronic imaging systems for earth observation on-board low-cost microsatellites.

This research programme has studied the possibilities and difficulties of using 50 kg microsatellites to perform remote imaging of the Earth. The design constraints of these missions are quite different to those encountered in larger, conventional spacecraft. While the main attractions of microsatellites are low cost and fast response times, they present the following key limitations: Payload mass under 5 kg, Continuous payload power under 5 Watts, peak power up to 15 Watts, Narrow communications bandwidths (9.6 / 38.4 kbps), Attitude control to within 5°, No moving mechanics. The most significant factor is the limited attitude stability. Without sub-degree attitude control, conventional scanning imaging systems cannot preserve scene geometry, and are therefore poorly suited to current microsatellite capabilities. The foremost conclusion of this thesis is that electronic cameras, which capture entire scenes in a single operation, must be used to overcome the effects of the satellite's motion. The potential applications of electronic cameras, including microsatellite remote sensing, have erupted with the recent availability of high sensitivity field-array CCD (charge-coupled device) image sensors. The research programme has established suitable techniques and architectures necessary for CCD sensors, cameras and entire imaging systems to fulfil scientific/commercial remote sensing despite the difficult conditions on microsatellites. The author has refined these theories by designing, building and exploiting in-orbit five generations of electronic cameras. The major objective of meteorological scale imaging was conclusively demonstrated by the Earth imaging camera flown on the UoSAT-5 spacecraft in 1991. Improved cameras have since been carried by the KITSAT-1 (1992) and PoSAT-1 (1993) microsatellites. PoSAT-1 also flies a medium resolution camera (200 metres) which (despite complete success) has highlighted certain limitations of microsatellites for high resolution remote sensing. A reworked, and extensively modularised, design has been developed for the four camera systems deployed on the FASat-Alfa mission (1995). Based on the success of these missions, this thesis presents many recommendations for the design of microsatellite imaging systems. The novelty of this research programme has been the principle of designing practical camera systems to fit on an existing, highly restrictive, satellite platform, rather than conceiving a fictitious small satellite to support a high performance scanning imager. This pragmatic approach has resulted in the first incontestable demonstrations of the feasibility of remote sensing of the Earth from inexpensive microsatellites

UAVs for the Environmental Sciences

This book gives an overview of the usage of UAVs in environmental sciences covering technical basics, data acquisition with different sensors, data processing schemes and illustrating various examples of application