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RADIOMETRIC CALIBRATION OF RADAR DEPTH SOUNDER DATA PRODUCTS
Talasila, Hara Madhav
Talasila, Hara Madhav
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Abstract
Although the Center for Remote Sensing and Integrated Systems (CReSIS) performs several radar calibration steps to produce Operation IceBridge (OIB) radar depth sounder data products, these datasets are not radiometrically calibrated. Scientific applications that estimate physical characteristics of surface and subsurface targets from the backscatter are limited with the current data because it is not absolutely calibrated. Moreover, intentional and unintentional changes in instrument hardware and processing methods for OIB over the last decade affect the quality of intercomparisons. Recent methods which interpret basal conditions and calculate signal attenuation using CReSIS OIB 2D radar depth sounder echograms are forced to use relative scattering power, rather than absolute methods.
As taking new measurements with a calibration target is not possible for past datasets, a data-dependent method that uses natural targets with known scattering characteristics is developed. Unsaturated natural target returns from smooth sea-ice leads or lakes are imaged in many datasets and have known scattering responses. The proposed method forms a system of linear equations with the recorded scattering signatures from these known targets, scattering signatures from crossing flight paths, and the radiometric correction terms. A least squares solution to optimize the radiometric correction terms is calculated, which minimizes the error function representing the mismatch in expected and measured scattering. The new correction terms are used to correct the remaining mission data. The radar depth sounder data from all OIB campaigns can be adjusted with these corrections to produce absolutely calibrated echograms for the Arctic and Antarctic. A software simulator is developed to study calibration errors and verify the calibration software. The software for processing natural targets and crossovers will be made available in CReSIS’s open-source Open Polar Radar software toolbox. The OIB data are adjusted with the new calibration terms, providing to the data user community a complete set of radiometrically calibrated radar echograms for the CReSIS OIB radar depth sounder for the first time.
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Date
2025-01-01
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University of Kansas
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This item contains archived web content.
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Talasila_ku_0099D_20002.pdf
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- Embargoed until 2176-05-31
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Keywords
Electrical engineering, Remote sensing, Electromagnetics, crossovers, full simulator, MCoRDS, natural target, radar depth sounder, radiometric calibration