Investigating Key Techniques to Leverage the Functionality of Ground/Wall Penetrating Radar

Ground penetrating radar (GPR) has been extensively utilized as a highly efficient and non-destructive testing method for infrastructure evaluation, such as highway rebar detection, bridge decks inspection, asphalt pavement monitoring, underground pipe leakage detection, railroad ballast assessment, etc. The focus of this dissertation is to investigate the key techniques to tackle with GPR signal processing from three perspectives: (1) Removing or suppressing the radar clutter signal; (2) Detecting the underground target or the region of interest (RoI) in the GPR image; (3) Imaging the underground target to eliminate or alleviate the feature distortion and reconstructing the shape of the target with good fidelity. In the first part of this dissertation, a low-rank and sparse representation based approach is designed to remove the clutter produced by rough ground surface reflection for impulse radar. In the second part, Hilbert Transform and 2-D Renyi entropy based statistical analysis is explored to improve RoI detection efficiency and to reduce the computational cost for more sophisticated data post-processing. In the third part, a back-projection imaging algorithm is designed for both ground-coupled and air-coupled multistatic GPR configurations. Since the refraction phenomenon at the air-ground interface is considered and the spatial offsets between the transceiver antennas are compensated in this algorithm, the data points collected by receiver antennas in time domain can be accurately mapped back to the spatial domain and the targets can be imaged in the scene space under testing. Experimental results validate that the proposed three-stage cascade signal processing methodologies can improve the performance of GPR system

ARRAY PROCESSING TECHNIQUES FOR ESTIMATION AND TRACKING OF AN ICE-SHEET BOTTOM

Ice bottom topography layers are an important boundary condition required to model the flow dynamics of an ice sheet. In this work, using low frequency multichannel radar data, we locate the ice bottom using two types of automatic trackers. First, we use the multiple signal classification (MUSIC) beamformer to determine the pseudo-spectrum of the targets at each range-bin. The result is passed into a sequential tree-reweighted message passing belief-propagation algorithm to track the bottom of the ice in the 3D image. This technique is successfully applied to process data collected over the Canadian Arctic Archipelago ice caps in 2014, and produce digital elevation models (DEMs) for 102 data frames. We perform crossover analysis to self-assess the generated DEMs, where flight paths cross over each other and two measurements are made at the same location. Also, the tracked results are compared before and after manual corrections. We found that there is a good match between the overlapping DEMs, where the mean error of the crossover DEMs is 38±7 m, which is small relative to the average ice-thickness, while the average absolute mean error of the automatically tracked ice-bottom, relative to the manually corrected ice-bottom, is 10 range-bins. Second, a direction of arrival (DOA)-based tracker is used to estimate the DOA of the backscatter signals sequentially from range bin to range bin using two methods: a sequential maximum a posterior probability (S-MAP) estimator and one based on the particle filter (PF). A dynamic flat earth transition model is used to model the flow of information between range bins. A simulation study is performed to evaluate the performance of these two DOA trackers. The results show that the PF-based tracker can handle low-quality data better than S-MAP, but, unlike S-MAP, it saturates quickly with increasing numbers of snapshots. Also, S-MAP is successfully applied to track the ice-bottom of several data frames collected from over Russell glacier in 2011, and the results are compared against those generated by the beamformer-based tracker. The results of the DOA-based techniques are the final tracked surfaces, so there is no need for an additional tracking stage as there is with the beamformer technique

Space-time sampling strategies for electronically steerable incoherent scatter radar

Incoherent scatter radar (ISR) systems allow researchers to peer into the ionosphere via remote sensing of intrinsic plasma parameters. ISR sensors have been used since the 1950s and until the past decade were mainly equipped with a single mechanically steerable antenna. As such, the ability to develop a two or three dimensional picture of the plasma parameters in the ionosphere has been constrained by the relatively slow mechanical steering of the antennas. A newer class of systems using electronically steerable array (ESA) antennas have broken the chains of this constraint, allowing researchers to create 3-D reconstructions of plasma parameters. There have been many studies associated with reconstructing 3-D fields of plasma parameters, but there has not been a systematic analysis into the sampling issues that arise. Also, there has not been a systematic study as to how to reconstruct these plasma parameters in an optimum sense as opposed to just using different forms of interpolation. The research presented here forms a framework that scientists and engineers can use to plan experiments with ESA ISR capabilities and to better analyze the resulting data. This framework attacks the problem of space-time sampling by ESA ISR systems from the point of view of signal processing, simulation and inverse theoretic image reconstruction. We first describe a physics based model of incoherent scatter from the ionospheric plasma, along with processing methods needed to create the plasma parameter measurements. Our approach leads to development of the space-time ambiguity function, forming a theoretical foundation of the forward model for ISR. This forward model is novel in that it takes into account the shape of the antenna beam and scanning method along with integration time to develop the proper statistics for a desired measurement precision. Once the forward model is developed, we present the simulation method behind the Simulator for ISR (SimISR). SimISR uses input plasma parameters over space and time and creates complex voltage samples in a form similar to that produced by a real ISR system. SimISR allows researchers to evaluate different experiment configurations in order to efficiently and accurately sample specific phenomena. We present example simulations using input conditions derived from a multi-fluid ionosphere model and reconstructions using standard interpolation techniques. Lastly, methods are presented to invert the space-time ambiguity function using techniques from image reconstruction literature. These methods are tested using SimISR to quantify accurate plasma parameter reconstruction over a simulated ionospheric region

Studies of the MLT/I using Multistatic Meteor Radar

This thesis applies a multistatic meteor radar to an investigation of the dynamics of the mesosphere lower thermosphere/ionosphere (MLT/I; 60-110 km altitude). The main radar used in the study operates at 55 MHz and is in the vicinity of Adelaide, South Australia, consisting of a monostatic radar at the Buckland Park eld site (34.6 S, 138.5 E) and a bistatic receiver located about 55 km south-east at a site in the Adelaide Hills (35.1 S, 138.8 E). The areas of investigation pertaining to MLT/I dynamics include assessing the ability of a multistatic meteor radar to measure the vertical ux of horizontal momentum and studying the interaction between gravity waves and tidal e ects. The thesis also presents a novel phase calibration technique for meteor radars, based on the use of civilian aircraft. The assessment of this radar's ability to measure MLT/I momentum uxes demonstrated that a relative uncertainty of about 75% can be expected for a monostatic con guration, assuming a ux magnitude of 20 m2s-2, a single day of integration, and a gravity wave field synthesized from a realistic spectral model. The multistatic configuration with a single bistatic receiver is shown to yield a relative uncertainty of about 65% under the same conditions. It is suggested that the increase in precision can be attributed entirely to the increase in the number of meteor detections associated with the combined monostatic and bistatic receivers, rather than due to the existence of a more favourable distribution of Bragg vectors arising from the receiver separation. A case study of winds around the autumnal equinox of 2018 revealed large modulations in diurnal tidal amplitudes, with peak component diurnal tide amplitudes of 50 ms-1 and peak zonal wind velocities of 140 ms-1. In the context of the need to verify the accuracy of momentum ux estimates from the radar, this motivated an investigation into the role momentum transport from gravity wave breaking played in modulating the tidal amplitudes. The investigation showed that while the observed gravity wave forcing exhibited a complex relationship with the tidal winds, the components of the forcing were generally seen to be approximately out of phase with the tidal winds above altitudes of 88 km. Additionally, no clear phase relationship between the tides and gravity wave forcing was observed below 88 km. Following the case study, the altitude and angle-of-arrival (AOA) errors and reduced meteor detection rates associated with suspected receiver phase calibration errors motivated the development of an alternative phase calibration technique. The technique developed was based on the use of echoes from civilian aircraft with known positions. Approximately two weeks worth of aircraft detections with the radar and a 1090 MHz Automatic Dependent Surveillance Broadcast receiver (used to receive aircraft position information) was acquired during November 2019. By taking into account the implied phase correction variability with AOA using a beamforming approach, it was shown that the aircraft-based corrections yielded an equal or smaller meteor height distribution width than the conventionally used empirical phase calibration technique. Assuming that a smaller height distribution width equates to smaller average height estimation errors, this was taken to mean that the aircraft-based approach outperformed the empirical one.Thesis (Ph.D.) -- University of Adelaide, School of Physical Sciences, 202

Annual meeting of the Lunar Exploration Analysis Group : October 22–24, 2012, Greenbelt, Maryland

The focus of this meeting will be a discussion of the ongoing contributions of the Apollo program to solar system exploration and options and opportunities for the next decade of lunar science and exploration. This meeting will include presentations and discussions on science objectives, robotic and human exploration strategies and technologies, critical required technology development commercial opportunities, education and outreach, and the Moon as a necessary stepping stone to the rest of the solar system.Sponsor: National Aeronautics and Space AdministrationConveners: Charles Shearer, University of New Mexico, Jeffrey Plescia, The John Hopkins Applied Physics Laboratory, Clive Neal, University of Notre Dame, Stephen Mackwell, Lunar and Planetary Institute.PARTIAL CONTENTS: Volatile Extraction and In Situ Resource Utilization for the Moon Applied to Near Earth Objects / E. H. Cardiff--A Revisit to Apollo Magnetic Field Records for Sounding of the Lunar Interior / P. J. Chi--LunarCube: Payload Development for Enhanced Yet Low Cost Lunar Exploration / P. E. Clark, R. MacDowall, R. Cox, A. Vasant, S. Schaire, and B. Malphrus--Frontier: Towards Onboard Intelligence for More Capable Next Generation Space Assets / P. E. Clark, M. L. Rilee, and S. A. Curtis--Near Real-Time Prospecting for Lunar Volatiles: Demonstrating RESOLVE Science in the Field / A. Colaprete, R. Elphic, J. Heldmann, K. Ennico, G. Mattes, and J. Sanders--Gateways to the Solar System: Innovative Advanced Magnet Lab Mass Driver Launch Platforms at L1 and L--R. Cox, P. Clark, A. Vasant, and R. Meinke--Modal Evaluation of Fluid Volume in Spacecraft Propellant Tanks / K. M. Crosby, R. Werlink, S. Mathe, and K. Lubick--Ground Data Systems for Real Time Lunar Science / M. C. Deans, T. Smith, D. S. Lees, E. B. Scharff, T. E. Cohen, and D. S. S. Lim

Advances in Sonar Technology

The demand to explore the largest and also one of the richest parts of our planet, the advances in signal processing promoted by an exponential growth in computation power and a thorough study of sound propagation in the underwater realm, have lead to remarkable advances in sonar technology in the last years.The work on hand is a sum of knowledge of several authors who contributed in various aspects of sonar technology. This book intends to give a broad overview of the advances in sonar technology of the last years that resulted from the research effort of the authors in both sonar systems and their applications. It is intended for scientist and engineers from a variety of backgrounds and even those that never had contact with sonar technology before will find an easy introduction with the topics and principles exposed here

Inversion Methods in Atmospheric Remote Sounding

The mathematical theory of inversion methods is applied to the remote sounding of atmospheric temperature, humidity, and aerosol constituents

BDS GNSS for Earth Observation

For millennia, human communities have wondered about the possibility of observing phenomena in their surroundings, and in particular those affecting the Earth on which they live. More generally, it can be conceptually defined as Earth observation (EO) and is the collection of information about the biological, chemical and physical systems of planet Earth. It can be undertaken through sensors in direct contact with the ground or airborne platforms (such as weather balloons and stations) or remote-sensing technologies. However, the definition of EO has only become significant in the last 50 years, since it has been possible to send artificial satellites out of Earth’s orbit. Referring strictly to civil applications, satellites of this type were initially designed to provide satellite images; later, their purpose expanded to include the study of information on land characteristics, growing vegetation, crops, and environmental pollution. The data collected are used for several purposes, including the identification of natural resources and the production of accurate cartography. Satellite observations can cover the land, the atmosphere, and the oceans. Remote-sensing satellites may be equipped with passive instrumentation such as infrared or cameras for imaging the visible or active instrumentation such as radar. Generally, such satellites are non-geostationary satellites, i.e., they move at a certain speed along orbits inclined with respect to the Earth’s equatorial plane, often in polar orbit, at low or medium altitude, Low Earth Orbit (LEO) and Medium Earth Orbit (MEO), thus covering the entire Earth’s surface in a certain scan time (properly called ’temporal resolution’), i.e., in a certain number of orbits around the Earth. The first remote-sensing satellites were the American NASA/USGS Landsat Program; subsequently, the European: ENVISAT (ENVironmental SATellite), ERS (European Remote-Sensing satellite), RapidEye, the French SPOT (Satellite Pour l’Observation de laTerre), and the Canadian RADARSAT satellites were launched. The IKONOS, QuickBird, and GeoEye-1 satellites were dedicated to cartography. The WorldView-1 and WorldView-2 satellites and the COSMO-SkyMed system are more recent. The latest generation are the low payloads called Small Satellites, e.g., the Chinese BuFeng-1 and Fengyun-3 series. Also, Global Navigation Satellite Systems (GNSSs) have captured the attention of researchers worldwide for a multitude of Earth monitoring and exploration applications. On the other hand, over the past 40 years, GNSSs have become an essential part of many human activities. As is widely noted, there are currently four fully operational GNSSs; two of these were developed for military purposes (American NAVstar GPS and Russian GLONASS), whilst two others were developed for civil purposes such as the Chinese BeiDou satellite navigation system (BDS) and the European Galileo. In addition, many other regional GNSSs, such as the South Korean Regional Positioning System (KPS), the Japanese quasi-zenital satellite system (QZSS), and the Indian Regional Navigation Satellite System (IRNSS/NavIC), will become available in the next few years, which will have enormous potential for scientific applications and geomatics professionals. In addition to their traditional role of providing global positioning, navigation, and timing (PNT) information, GNSS navigation signals are now being used in new and innovative ways. Across the globe, new fields of scientific study are opening up to examine how signals can provide information about the characteristics of the atmosphere and even the surfaces from which they are reflected before being collected by a receiver. EO researchers monitor global environmental systems using in situ and remote monitoring tools. Their findings provide tools to support decision makers in various areas of interest, from security to the natural environment. GNSS signals are considered an important new source of information because they are a free, real-time, and globally available resource for the EO community