65,202 research outputs found

    TU1208 open database of radargrams. the dataset of the IFSTTAR geophysical test site

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    This paper aims to present a wide dataset of ground penetrating radar (GPR) profiles recorded on a full-size geophysical test site, in Nantes (France). The geophysical test site was conceived to reproduce objects and obstacles commonly met in the urban subsurface, in a completely controlled environment; since the design phase, the site was especially adapted to the context of radar-based techniques. After a detailed description of the test site and its building process, the GPR profiles included in the dataset are presented and commented on. Overall, 67 profiles were recorded along eleven parallel lines crossing the test site in the transverse direction; three pulsed radar systems were used to perform the measurements, manufactured by different producers and equipped with various antennas having central frequencies from 200 MHz to 900 MHz. An archive containing all profiles (raw data) is enclosed to this paper as supplementary material. This dataset is the core part of the Open Database of Radargrams initiative of COST (European Cooperation in Science and Technology) Action TU1208 “Civil engineering applications of Ground Penetrating Radar”. The idea beyond such initiative is to share with the scientific community a selection of interesting and reliable GPR responses, to enable an effective benchmark for direct and inverse electromagnetic approaches, imaging methods and signal processing algorithms. We hope that the dataset presented in this paper will be enriched by the contributions of further users in the future, who will visit the test site and acquire new data with their GPR systems. Moreover, we hope that the dataset will be made alive by researchers who will perform advanced analyses of the profiles, measure the electromagnetic characteristics of the host materials, contribute with synthetic radargrams obtained by modeling the site with electromagnetic simulators, and more in general share results achieved by applying their techniques on the available profiles

    Verification and Calibration of the ICEBEAR Radar through GPU Acceleration, Noise Characterization and Calculation, and Radio Galaxy Phase Calibration

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    The research performed for this thesis focused on verifying, quantifying, calibrating, and improving the Ionospheric Continuous Wave (CW) E-region Bi-static Radar (ICEBEAR) data observations and quality. Graphical processing unit (GPU) acceleration was used to improve the computation speed of ICEBEAR data analysis. The ICEBEAR noise floor was studied to better understand the ICEBEAR noise environment and verify the signal to noise ratio (SNR), which affects all ICEBEAR data products. Finally, a calibration method using the radio galaxy Cygnus~A was developed to enable improved phase calibration of the ICEBEAR receiver antennas. GPUs enable high computational throughput through the use of parallel processing and specific hardware design. This part of my research used the properties of GPUs to accelerate the data analysis of ICEBEAR to be 48 times faster than the original processing capability, enabling real-time analysis of ICEBEAR data. The current noise calculation technique of taking the median power calculation of the ICEBEAR field of view is reasonable, but it is recommended that ICEBEAR switch to using an average of the furthest ranges measured by the radar. The dominant noise sources in the radar changes based on ionospheric activity, where self-clutter dominates during active periods and cosmic noise dominates during quite periods. This impacts the computation of the SNR data product and is better quantified by a far range average for all 45 baselines in the ICEBEAR radar. The detection of Cygnus~A during quiet ionospheric periods was used to calculate phase self-calibrations for the radar by comparing the measured phase difference between antennas to the expected theoretical phase difference of Cygnus~A. The technique is shown to generate similar and complementary results to the current spectrum analyzer calibration technique. Future improvements to ICEBEAR imaging analysis and future research into the improved observation of Cygnus~A will allow this new phase self-calibration method to be actively used for ICEBEAR

    An Extended Virtual Aperture Imaging Model for Through-the-wall Sensing and Its Environmental Parameters Estimation

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    Through-the-wall imaging (TWI) radar has been given increasing attention in recent years. However, prior knowledge about environmental parameters, such as wall thickness and dielectric constant, and the standoff distance between an array and a wall, is generally unavailable in real applications. Thus, targets behind the wall suffer from defocusing and displacement under the conventional imag¬ing operations. To solve this problem, in this paper, we first set up an extended imaging model of a virtual aperture obtained by a multiple-input-multiple-output array, which considers the array position to the wall and thus is more applicable for real situations. Then, we present a method to estimate the environmental parameters to calibrate the TWI, without multiple measurements or dominant scatter¬ers behind-the-wall to assist. Simulation and field experi¬ments were performed to illustrate the validity of the pro¬posed imaging model and the environmental parameters estimation method

    The WISDOM Radar: Unveiling the Subsurface Beneath the ExoMars Rover and Identifying the Best Locations for Drilling

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    The search for evidence of past or present life on Mars is the principal objective of the 2020 ESA-Roscosmos ExoMars Rover mission. If such evidence is to be found anywhere, it will most likely be in the subsurface, where organic molecules are shielded from the destructive effects of ionizing radiation and atmospheric oxidants. For this reason, the ExoMars Rover mission has been optimized to investigate the subsurface to identify, understand, and sample those locations where conditions for the preservation of evidence of past life are most likely to be found. The Water Ice Subsurface Deposit Observation on Mars (WISDOM) ground-penetrating radar has been designed to provide information about the nature of the shallow subsurface over depth ranging from 3 to 10 m (with a vertical resolution of up to 3 cm), depending on the dielectric properties of the regolith. This depth range is critical to understanding the geologic evolution stratigraphy and distribution and state of subsurface H2O, which provide important clues in the search for life and the identification of optimal drilling sites for investigation and sampling by the Rover's 2-m drill. WISDOM will help ensure the safety and success of drilling operations by identification of potential hazards that might interfere with retrieval of subsurface samples
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