Polarimetric calibration of spaceborne and airborne multifrequency SAR data for scattering-based characterization of manmade and natural features

Polarimetric calibration of spaceborne and airborne multifrequency SAR data for scattering-based characterization of manmade and natural features

Kumar, Shashi (Indian Institute of Remote Sensing)
Babu, Arun (Indian Institute of Remote Sensing; Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR))
Agrawal, Shefali (Indian Institute of Remote Sensing)
Asopa, U. (TU Delft Mathematical Geodesy and Positioning; Indian Institute of Remote Sensing)
Shukla, S. (TU Delft Physical and Space Geodesy; Indian Institute of Remote Sensing; International Institute for Geo-Information Science and Earth Observation (ITC))
Maiti, Abhisek (Indian Institute of Remote Sensing; International Institute for Geo-Information Science and Earth Observation (ITC))

2022

The Polarimetric Synthetic Aperture Radar (PolSAR) systems use electromagnetic radiations of different polarizations in the microwave frequency to collect the scattering information from targets on the Earth. Nevertheless, as with any other electronic device, the PolSAR systems are also not ideal and subjected to distortions. The most important of these distortions are the polarimetric distortions caused due to the channel imbalance, phase bias, and crosstalk between the different polarization channels. For the spaceborne PolSAR systems, the Earth's ionosphere also contributes to an additional polarimetric distortion known as the Faraday rotation. An effort was made in this study to perform the polarimetric calibration of the Quad-pol and Compact-pol PolSAR datasets acquired using different airborne and spaceborne PolSAR systems to estimate and minimize these polarimetric distortions. The investigation was also done to analyze the impact of these polarimetric distortions on the scattering mechanisms from ground targets and on its dependency on the radar wavelength. The study was done using the UAVSAR L-band Quad-pol dataset, RADARSAT-2 Quad-pol dataset, ALOS-2 PALSAR-2, ISRO's L&S- Band Airborne SAR (LS-ASAR) Quad-pol and Compact-pol datasets, and the RISAT-1 Compact-pol dataset. Calibration of the airborne PolSAR data was carried to understand the level of polarimetric distortions in the LS-ASAR product that is a precursor mission to the spaceborne Dual-Frequency L&S Band NASA-ISRO Synthetic Aperture Radar (NISAR) mission. It is understood that the crosstalk is the dominant polarimetric distortion, which severely affects the PolSAR datasets compared to the other polarimetric distortions, and it is more for the higher wavelength PolSAR systems. The Quegan, Improved Quegan, and Ainsworth algorithms for crosstalk estimation and minimization was performed for the different Quad-pol datasets and it was found that the Improved Quegan algorithm is suitable for removing crosstalk from datasets having high crosstalk and the Ainsworth algorithm is suitable for removing crosstalk from datasets having low crosstalk. The Freeman method of the polarimetric calibration was implemented for the compact-pol datasets and it was able to considerably minimize the polarimetric distortions. The coherency matrix, scattering matrix, model-based decomposition, polarimetric signatures, and roll invariant parameter-based analysis revealed that all the datasets after polarimetric calibration were showing the correct scattering responses expected from the ground targets.

Ainsworth algorithm
Channel imbalance
Crosstalk
CTLR
Faraday rotation
Freeman algorithm
Improved Quegan algorithm
NASA-ISRO Synthetic Aperture Radar (NISAR)
Phase bias
Polarimetric decomposition
Quegan algorithm
Spaceborne PolSAR

http://resolver.tudelft.nl/uuid:cc799877-64f3-4368-ac61-7fb7956e31fb

https://doi.org/10.1016/j.asr.2021.02.023

2023-07-01

0273-1177

Advances in Space Research, 69 (4), 1684-1714

Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.

Institutional Repository

journal article

© 2022 Shashi Kumar, Arun Babu, Shefali Agrawal, U. Asopa, S. Shukla, Abhisek Maiti