Earth & Space Science

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https://hdl.handle.net/10315/27626

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Open Access
Generic on-board-computer hardware and software development for nanosatellite applications
(2012-11) Borschiov, Konstantin; Lee, Regina; Quine, Brendan
This study outlines the results obtained from the development of a generic nanosatellite on-board-computer (OBC). The nanosatellite OBC is a non-mission specific design and as such it must be adaptable to changing mission requirements in order to be suitable for varying nanosatellite missions. Focus is placed on the commercial-off-the-shelf (COTS) principle where commercial components are used and evaluated for their potential performance in nanosatellite applications. The OBC design is prototyped and subjected to tests to evaluate its performance and its feasibility to survive in space.
Open Access
Dynamics and Control of Smart Structures for Space Applications
(2014-07-09) Orszulik, Ryan Russell; Shan, Jinjun
Smart materials are one of the key emerging technologies for a variety of space systems ranging in their applications from instrumentation to structural design. The underlying principle of smart materials is that they are materials that can change their properties based on an input, typically a voltage or current. When these materials are incorporated into structures, they create smart structures. This work is concerned with the dynamics and control of three smart structures: a membrane structure with shape memory alloys for control of the membrane surface flatness, a flexible manipulator with a collocated piezoelectric sensor/actuator pair for active vibration control, and a piezoelectric nanopositioner for control of instrumentation. Shape memory alloys are used to control the surface flatness of a prototype membrane structure. As these actuators exhibit a hysteretic nonlinearity, they need their own controller to operate as required. The membrane structures surface flatness is then controlled by the shape memory alloys, and two techniques are developed: genetic algorithm and proportional-integral controllers. This would represent the removal of one of the main obstacles preventing the use of membrane structures in space for high precision applications, such as a C-band synthetic aperture radar antenna. Next, an adaptive positive position feedback law is developed for control of a structure with a collocated piezoelectric sensor/actuator pair, with unknown natural frequencies. This control law is then combined with the input shaping technique for slew maneuvers of a single-link flexible manipulator. As an alternative to the adaptive positive position feedback law, genetic algorithms are investigated as both system identification techniques and as a tool for optimal controller design in vibration suppression. These controllers are all verified through both simulation and experiments. The third area of investigation is on the nonlinear dynamics and control of piezoelectric actuators for nanopositioning applications. A state feedback integral plus double integral synchronization controller is designed to allow the piezoelectrics to form the basis of an ultra-precise 2-D Fabry-Perot interferometer as the gap spacing of the device could be controlled at the nanometer level. Next, an output feedback linear integral control law is examined explicitly for the piezoelectric actuators with its nonlinear behaviour modeled as an input nonlinearity to a linear system. Conditions for asymptotic stability are established and then the analysis is extended to the derivation of an output feedback integral synchronization controller that guarantees global asymptotic stability under input nonlinearities. Experiments are then performed to validate the analysis. In this work, the dynamics and control of these smart structures are addressed in the context of their three applications. The main objective of this work is to develop effective and reliable control strategies for smart structures that broaden their applicability to space systems.
Open Access
Development of a Multi-Projection Approach for Global Web Map Visualization
(2014-07-09) Girin, Ignat; Pagiatakis, Spiros D.
The popularity of web mapping services such as Google and Bing Maps is growing. However, professional users experience several limitations while using these on-line mapping services. The first problem is the limited global coverage. The coverage ends at latitude of 85° north and south. The second problem is the systematic distortion that increases with latitude. For example, in Google Maps Greenland appears to be larger than South America, whereas in reality Greenland is 8 times smaller. The third problem is the lack of mathematical rigour for the cartographic projections because the Earth is treated as a sphere instead of an ellipsoid. Thus, a better web mapping system is needed for professional users and users interested in polar regions. This thesis presents a multi-projection approach for global web map visualization. The multi-projection approach minimizes the cartographic distortions by using different projections across the globe and for ranges of mapping detail levels.
Open Access
Planetary Micro-Rovers with Bayesian Autonomy
(2014-07-09) Post, Mark Andrew; Quine, Brendan
In this dissertation, we present the Beaver μrover, a 6kg solar-powered planetary rover that is designed to perform exploration missions such as the Northern Light Mars mission, as well as to extend the capabilities of modern robotics here on Earth. By developing systems from the ground up using a pragmatic design approach for modularity and expandability, commercial hardware, open-source software, and novel implementations of probabilistic algorithms, we have obtained a comprehensive set of hardware and software designs that can form the basis for many kinds of intelligent but low-cost robots. A lightweight tubular chassis that can be simply deployed protects sensors, actuators, and wiring, and a novel four-wheel independently driven and passively actuated suspension with enclosed brushless gear motors can stably handle steep slopes and low obstacles. A nanosatellite-sized electronics stack incorporates Linux or dedicated RTOS computing on the ARM architecture, highly-efficient battery charging and power conversion, MEMS and external sun sensors, a powerful hybrid motor controller, and a vision system. Separate rovers and programmable components communicate using a novel network communications architecture over synchronous serial buses and mesh network radio communications. Intelligent autonomy is made possible using probabilistic methods programmed with fixed-point arithmetic for efficiency, incorporating Kalman filters and a Bayesian network constructed both from prior knowledge and from the implicit structure of the hardware and software present and used for inference and decision-making. Navigation makes use of both external sensors and visual SLAM by using optical flow and structure-from-motion methods. Detailed descriptions and comparisons of all systems are given, and it is shown that using a basic set of sensors and the vision system, basic navigational and problem-solving tasks can be performed. Thermal vacuum testing of components is also done to validate their operation under space conditions.
Open Access
Design and Test of a Slab Waveguide Spectrometer for Spatial Heterodyne Observations of Water Vapor
(2014-07-28) Sinclair, Kenneth Allan; Quine, Brendan
The Slab Waveguide Interferometric Spatial Heterodyne (SWISH) Spectrometer was designed as a high-resolution instrument designed to demonstrate the ability of slab waveguide spatial heterodyne spectrometer technology through measurements of water vapor in Earth’s atmosphere. It is based on a multiaperture Fourier-transform planar waveguide spectrometer. The Fourier technique was used for spectra retrieval. The absorption signal will be measured with a spectral range of 2.5 nm centered in the near infrared spectral region on the 1.3645 μm wavelength with a spectral resolution of 0.05 nm. The resolution of the interferometer array is designed so that errors in the retrieved spectrum, measured using the least squares method, are minimized. The slab waveguide itself was constructed such that the interferometers and monitoring waveguides have an output pitch, which matches that of the linear detector array. It was designed for the 1.3645 μm wavelength range using a 1.3 μm wide and 0.75 μm high silicon-on-insulator (SOI) ridge waveguides and contained 100 Mach-Zehnder interferometers along with 11 'pass-through' waveguide. This thesis spans several components of the project relating to the development and testing of the SWISH Spectrometer. These parts include: (1) developing and building a prototype slab waveguide spatial heterodyne spectrometer (SWSHS) chip and breadboard optical instrument at spatial heterodyne observations of water (SHOW) wavelengths; (2) investigating alternative method(s) for increased coupling efficiency; (3) assembling a prototype spectrometer for SHOW waveband; (4) assembling input optics for the SWSHS; (5) developing system packaging and build a prototype system; (6) developing inversion algorithms and calibration procedures for system using test data from laboratory tests of micro-SHOW linear prototype.
Open Access
CMOS Imager for Nanosatellite Applications
(2014-10) Irvin, Patrick Edward Garret; Lee, Regina S. K.
This research examines the capabilities of Commercial-off-the-shelf CMOS image sensors for use on nanosatellites as a star tracker. An emphasis is placed on selecting low cost components that meet the restrictions on mass and power of nanosatellites. To determine the expected sky coverage a Monte Carlo simulation is used with different limiting magnitudes and orbits. An image sensor, and lens system are selected and are interfaced using a Field Programmable Gate Array for data processing. The camera is then characterized in lab before being tested imaging the night sky.
Open Access
Development of Magnetometer-Based Orbit and Attitude Determination for Nanosatellites
(2015-01-26) Wright, Thomas Jonathan; Bisnath, Sunil B.; Lee, Regina
Attitude and orbit determination are critical parts of nanosatellite mission operations. The ability to perform attitude and orbit determination autonomously could lead to a wider array of mission possibilities for nanosatellites. This research examines the feasibility of using low-cost magnetometer measurements as a method of autonomous, simultaneous orbit and attitude determination for the novel application of redundancy on nanosatellites. Extended Kalman Filters (EKFs) are developed for attitude determination and orbit determination. Simulations are run to compare the developed systems with previous work on attitude and orbit determination. The EKFs are combined to provide both attitude and orbit determination simultaneously. Simulations show that this approach for simultaneous, autonomous attitude and orbit determination on nanosatellites provides 8.5 degrees and 12.5 km of attitude and orbit knowledge, respectively. The results of the simulations are then validated using Hardware-In-The-Loop testing. Additionally, a Helmholtz cage is evaluated for future use in the Hardware-In-The-Loop test setup.
Open Access
Applications for FPGA's on Nanosatellites
(2015-01-26) Thai, Thong; Lee, Regina
This thesis examines the feasibility of using a Field Programmable Gate Array (FPGA) based design on-board a CubeSat-sized nanosatellite. FPGAs are programmable logic devices that allow for the implementation of custom digital hardware on a single Integrated Circuit (IC). By using these FPGAs in spacecraft, more efficient processing can be done by moving the design onto hardware. A variety of different FPGA-based designs are looked at, including a Watchdog Timer (WDT), a Global Positioning System (GPS) receiver, and a camera interface.
Open Access
Carbon Data Assimilation Using an Ensemble Kalman Filter
(2015-01-26) Miao, Nan; Chen, Yongsheng
As a first step to build an ensemble data assimilation and source inversion system for atmospheric carbon, I implemented column-integrated carbon monoxide (CO) mixing ratio assimilation capability in an ensemble Kalman filter (EnKF) data assimilation system with the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem). In spite of its global coverage, the CO retrievals from the Measurements Of Pollution In The Troposphere (MOPITT) instrument onboard the Terra satellite are available only once per day. There has been restricted use of these CO data for atmospheric chemistry forecasting. Data assimilation provides an effective way to guide the model in time. This WRF-Chem/EnKF system has been tested for a real forest fire case in British Columbia in 2010. It has been observed that after assimilating MOPITT data, the model has been constrained closer toward the observations and the root-mean-square errors (RMSE) between the forecasts and the observations have been reduced. An inverse modeling of CO sources using parameter estimation with an EnKF was also performed. Comparisons of the assimilated CO profiles with optimal emissions to observations indicate that the assimilation leads to a considerable improvement of the model simulations as compared with a control run with no assimilation. Model biases in the simulation of background values are reduced and an improvement in the simulation of very high concentrations is observed.
Open Access
A Large Scale Simulation of Satellites Tracking Vessels and Other Targets
(2015-01-26) Wisnarama, Sriyan Indrajith; Lee, Regina
This research outlines the design of a large scale simulation of satellites tracking large amounts of dynamic targets. The use of such a simulation is presented and current solutions available are presented. The research sets out a list of objectives to meet by creating an application programming interface (API) that have the requirements of being efficient, scalable, flexible, and easy to use for the implementer. Methods of creating sections of the simulation such as the attitude motion of a satellite based on the physical characteristics of nanosatellites is explored and developed. The creation of targets that are contained only on certain land features are also developed and tested. The objectives set out are tested by creating a simulation using the API developed and the results are presented.
Open Access
An Offshore Wind Resource Assessment and a Look into Model Errors in Wind Forecasts
(2015-08-12) Corkum, Matthew Brenton; Taylor, Peter
This dissertation will look at 3 related, but different topics. The rst, is a VHF wind proler network in Southern Ontario and Quebec, the OQnet that provides real time wind measurements from 500m - 12000m. This study will look at ways of validating the data from these prolers and comparing them to forecast models such as the Canadian GEM model in Chapter 2. The second part of this thesis will look at offshore wind resource assessment. Wind energy is a clean and viable alternative to burning fossil fuels for energy and is being expanded all over the world. Europe is a global leader when it comes to wind energy and they have expanded this industry to include many offshore wind farms. As Canada looks to accelerate their wind energy production, companies have begun to study the offshore wind resource in the Great Lakes. In 2010, Toronto Hydro started a 2 year wind resource campaign. The lidar installed by Toronto Hydro measured wind speed and direction up to hub height over a 2 year period but there were many gaps in the record. Other instruments, installed by the York University team measured platform level winds and other weather variables. Using a combination of lidar extrapolation and platform level winds a continuous series of hub height winds has been generated which is discussed in Chapter 3. Chapter 4 looks at using these data to look at Measure, Correlate, Predict (MCP) estimations of long term wind speed. Chapter 5 looks at Annual Energy Production (AEP) estimates for two potential wind farm designs for the Toronto Hydro site. Finally in Chapter 6, this dissertation looks at issues related to wind forecasting for these wind farms and what kind of errors are associated with wind energy forecasts.
Open Access
DTM Generation in Forested Areas from Full-Waveform Airborne LiDAR Data
(2015-08-28) Gumerov, Damir; Hu, Baoxin
This study was aimed at improving overall quality of Digital Terrain Model (DTM) extraction from full-waveform LiDAR data. Specifically, the primary goal was to develop a novel method to improve DTM extraction by utilizing low amplitude pulses that are generated by terrain under vegetation, but undetectable using traditional Gaussian decomposition techniques. The secondary objective was to validate the developed methodology using ground reference data. An integrated approach was developed to detect weak returns backscattered by the bare terrain using full-waveform data and implemented using Microsoft Visual Studio. In this approach, echo detection, identification of terrain points, and generation of the triangulated irregular network (TIN) were iteratively carried out. To validate the proposed method, airborne LiDAR datasets obtained from a Riegl’s LMS-Q560 over five study sites in the Great Lakes-St. Lawrence forest region near Sault Ste. Marie, Ontario, Canada were used. The generated DTMs were compared with those obtained from the commercial software, TerraSolid’s TerraScan, based on ground measurements. The validation results show that using the developed method, the improvement in DTM was up to 21% for the five study areas, but up to 29% only considering heavily wooded areas with variable terrain. In addition, the developed methodology demonstrated an increase in LiDAR density and coverage of terrain points detected (up to 10-15%), when compared to TerraScan’s ground extraction routine.
Open Access
Determining Amplitude Corrections for the Assessment of Surface Roughness Within A Lidar Footprint
(2015-08-28) Midwinter, Calvin Weber; Daly, Michael
The research presented in this thesis is under the context of the OSIRIS-REx mission, a NASA led asteroid sample return mission being launched in 2016 towards the asteroid 101955 Bennu. Aboard the spacecraft is the OSIRIS-REx Laser Altimeter (OLA), which is using the backscattered intensity for instrument calibration. By applying the novel solution of amplitude correction, it is possible to gain additional functionality out of this instrument. This thesis presents a simulation written by the author that accurately models laser altimeter performance. The simulation is used successfully to study OLA’s receiver to reduce error in the range measurements and to remove the effects of large-scale topographic features on the amplitude. The remaining amplitude variations will be interpreted as mineralogical or morphological variations that may impact the viability or the desirability of the site for sample collection.
Open Access
FPGA-Based Software GNSS Receiver Design for Satellite Applications
(2015-08-28) Guruprasad, Surabhi; Bisnath, Sunil B.
Global Navigation Satellite System (GNSS) receiver technology has tremendous scope for satellite applications such as radio occultation, precise orbit determination and reflectometry. Spaceborne GNSS receivers are characterised by low power requirements, high processing speed and radiation resistant electronic components. Such sophisticated receivers, also called hardware GNSS receivers, are fabricated for specific applications and hence lack design flexibility. On the other hand, a software GNSS receiver allows easy design modifications without any hardware component replacement. Software receivers employ reconfigurable hardware elements called Field Programmable Gate Arrays (FPGAs). In this research, a low-power, low-cost software GNSS receiver has been designed and developed using a combination of a microprocessor and FPGA (System-on-Chip or SoC). The developed software GNSS receiver is capable of detecting GPS satellites, tracking them and computing receiver position estimates. Efficient task partitioning is achieved by implementing operations in both, the FPGA and the microprocessor. Also demonstrated is the improvement of processing speed by 20% when certain GNSS receiver operations are performed in the FPGA instead of the microprocessor.
Open Access
Effective Broadband Permittivity Measurements of Geological Materials
(2015-08-28) Sotodeh, Shahroukh; Daly, Michael
It is a commonly held belief that broadband permittivity measurement techniques have great uncertainties in dielectric loss for low-loss materials, which is unfavourable for applications in planetary and asteroid radar mapping. While true, much of the literature has neglected to address in detail how accurate and effective broadband permittivity measurements truly are. The optimal accuracy is often cited as ± 5% for low to medium loss materials [1]. This thesis reports on the development of a procedure to perform the most accurate and repeatable permittivity measurements of granular materials using a coaxial airline. A detailed uncertainty analysis comprising all sources of uncertainty is presented. Measurements of materials with well-known dielectric properties are performed in order to validate the reliability of the laboratory setup, refined sample handling, and measurement procedure. Although the results suggest this as a reliable technique for dielectric constant measurements, they reaffirm the conclusion of poor accuracy in dielectric loss measurements.
Open Access
Multi-GNSS Precise Point Positioning Software Architecture and Analysis of GLONASS Pseudorange Biases
(2015-08-28) Aggrey, John Egyir; Bisnath, Sunil B.
With expanding satellite-based navigation systems, multi-Global Navigation Satellite System (GNSS) Precise Point Positioning (PPP) presents an advantage over a single navigation system, which improves position accuracy and enhances availability of satellites and signals. The York GNSS PPP software was developed using C++ in the Microsoft.Net platform to utilize the existing multi-GNSS satellite constellations based on the software processor used by the Natural Resources Canada (NRCan) PPP online service. The software was built as a robust, scalable, modular tool that meets the highest of scientific standards compared to existing online PPP engines.There exists a correlation between receiver stations from heterogeneous networks, such as the IGS, in GNSS PPP processing and the increase in magnitude of the pseudorange and carrier-phase biases in both GPS + GLONASS and GLONASS-only PPP solutions. The correlation is due to mixed receiver and antenna hardware as well as firmware versions. Unlike GPS, GLONASS observations are affected by the Frequency Division Multiple Access (FDMA) satellite signal structure, which introduces inter-frequency channel biases and other system biases. The GLONASS pseudorange inter-channel frequency biases show a strong correlation with different receiver types, firmware versions and antenna types. This research estimated the GLONASS pseudorange inter-frequency channel biases using 350 IGS stations, based on 32 receiver types and 4 antenna types over a period of one week. An improvement of 19% was observed after calibrating for the pseudorange ICBs, in the horizontal components respectively, considering 20 minutes convergence period.
Open Access
Wind Turbine Impacts on Environment Canada Weather Radar Data
(2015-08-28) Rennie, Carolyn Jean; Taylor, Peter
This thesis investigates the occurrence of wind turbine clutter (WTC) on Canadian weather radar data and provides a detailed comparison to expectations from developed radar line of sight (RLOS) tools for three wind farms under standard atmospheric conditions. Tools were developed to study factors which impact WTC such as wind turbine orientation, and atmospheric propagation of the radar beam using atmospheric profile data. The results indicate that standard methods of RLOS calculations may need to take into account other factors as WTC was observed even when RLOS tools indicated the wind turbines would not intercept the main radar beam. Additionally, Canadian Turbine Interference Products (C-TRIP) were created in order to assist Environment Canada’s meteorologists in the identification of WTC given existing wind farm locations.
Open Access
Single Tree Detection from Airborne Laser Scanning Data: A Stochastic Approach
(2015-08-28) Zhang, Junjie; Sohn, Gunho
Characterizing and monitoring forests are of great scientific and managerial interests, such as understanding the global carbon circle, biodiversity conservation and management of natural resources. As an alternative or compliment to traditional remote sensing techniques, airborne laser scanning (ALS) has been placed in a very advantageous position in forest studies, for its unique ability to directly measure the distribution of vegetation materials in the vertical direction, as well as the terrain beneath the forest canopy. Serving as basis for tree-wise forest biophysical parameter and species information retrieval, single tree detection is a very motivating research topic in forest inventory. The objective of the study is to develop a method from the perspective of computer vision to detect single trees automatically from ALS data. For this purpose, this study explored different aspects of the problem. It starts from an improved pipeline for canopy height model (CHM) generation, which alleviates the distortion of tree crown shapes presented on CHMs resulted from conventional procedures due to the shadow effects of ALS data and produces pit-free CHM. The single tree detection method consists of a hybrid framework which integrates low-level image processing techniques, i.e. local maxima filtering (LM) and marker-controlled watershed segmentation (MCWS), into a high-level probabilistic model. In the proposed approach, tree crowns in the forest plot are modelled as a configuration of circular objects. The configuration containing the best possible set of detected tree objects is estimated by a global optimization solver in a probabilistic framework. The model features an accelerated optimization process compared with classical stochastic models, e.g. marked point processes. The parameter estimation is another issue: the study investigated both a reference-based supervised and an Expectation-Maximization (EM) based unsupervised method to estimate the parameters in the model. The model was tested in a temperate mature coniferous forest in Ontario, Canada, as well as simulated coniferous forest plots with various degrees of crown overlap. The experimental results showed the effectiveness of our proposed method, which was capable of reducing the commission errors produced by local maxima filtering based methods, thus increasing the overall detection accuracy by approximately 10% on all of the datasets.
Open Access
Dynamics in the Anvil Outflow of Tropical Convection
(2015-08-28) Lederman, Jerusha Isabel; Pagiatakis, Spiros D.
This thesis presents results of an experiment to investigate the dynamics of air motions within the outflow of tropical deep convection in the upper troposphere above Darwin, Australia. The research involved analyzing in situ measurements within the anvil outflow from the Egrett aircraft and also coincident laser remote sensing measurements of cloud structure from a King Air aircraft, flying directly below the Egrett. The data included the only in situ turbulence measurements that have been obtained with a resolution of 4 meters inside of an anvil outflow. The research shows that gravity waves and coherent structures exist in the anvil outflow. High frequency gravity waves were identified from the 90ᵒ phase lag between temperature and vertical wind oscillations. The gravity waves had wavelengths of 2 – 5 km and were observed as isolated waves with less than two oscillations, or, as extended waves with several oscillations. In some instances, correlations between temperature and vertical wind oscillations had zero phase lag between them and this was consistent with Rayleigh-Bénard convective rolls. Turbulence in the outflow was observed to be intense within patches separated by more quiescent flow. This turbulence had some characteristics that were unique in comparison to previous turbulence measurements at similar altitudes in the jet stream or midlatitude cirrus clouds. The ratio of the power spectral density of vertical wind fluctuations to the horizontal wind fluctuations was greater in the anvil outflow in comparison to the measurements in turbulence generated by shear in mid latitude jet stream and cirrus clouds. The relative magnitude of the vertical wind fluctuation spectrum decreases at all wavelengths with increasing distance away from the core region of the storm. This constitutes the first evidence that is consistent with theoretical predictions of “stratified turbulence.” Measurements in flights above and below the outflow base indicate that momentum flux is directed both upward and downward, away from the cloud base. This suggests the combination of shear and undulations in the cloud base are a mechanism for generating the observed high frequency gravity waves. This mechanism has not been previously identified from measurements or theoretical modelling and thus adds to our knowledge of processes that transport constituents and momentum within the tropical upper troposphere.
Open Access
Dynamic Modeling and Control System Design for Shape Memory Alloy Actuators
(2015-08-28) Kim, In Seon; Shan, Jinjun
Shape memory alloy (SMA) is a type of smart material which remembers its original state. It is light weight and small, and known to provide high contraction force with low noise. Its application has wide range from robotics to medical science. One of its potential applications in space is a supporting system of membrane structure that can be used as synthetic aperture radar (SAR) antenna to achieve high flatness. It exhibits nonlinear phenomena called hysteresis when it's electrically heated. Hysteresis is a nonlinear phenomenon that refers to the dependence of a physical system on the environment. Hysteresis in SMA causes a major difficulty in control system design. Un-modeled or poorly modeled hysteresis introduces inaccuracy in tracking and the performance of the system. Experimental test bench is constructed for one set of SMA actuators that resembles the membrane structure's supporting system. Hysteresis is obtained by running open loop test with the test bench. Dynamic model of the SMA wires is developed using classical Preisach model and modified Maxwell model. Then the inverse model is implemented in feed-forward loop to compensate for nonlinear hysteresis. Simple feedback controllers are added to correct the modeling errors. Experimental results reveal that the error is significantly reduced when comparing feedback controller with hybrid feedback and feed-forward controller.