Improved Faraday Rotation Estimation in Spaceborne PolSAR Data Using Total Variation Denoising

Wulong Guo,Haisheng Zhao,Bo Liu,Cheng Wang,Lu Liu,Liang Chen

doi:10.3390/rs11242943

Abstract

Faraday rotation (FR) is a serious problem for spaceborne polarization SAR (PolSAR) systems at L and P bands. One way to solve the problem is to estimate the FR from PolSAR data for further compensation. Therefore, precise estimation of FR from PolSAR data not only determines the compensation effect of polarimetric systems but also benefits the ionospheric sounding with high spatial resolution. Among the factors that affect the FR estimation, system noise is a non-neglectable factor. Although average filtering (AF) has been widely used in previous works for noise removing it depends on large window size, and therefore reduces the spatial resolution of FR estimation. In order to realize optimal noise suppression with minimized resolution loss, the total variation (TV) denoising method is applied in this paper. By testing the Advanced Land Observing Satellite (ALOS) Phased Array L-band Synthetic Aperture Radar (PALSAR) full-pol datasets, TV and AF are compared and validated. Results using synthetic and real data show that, after TV denoising, the FR can be recovered with high spatial resolution and the noise level in estimated FR is reduced more effectively than that after AF.

Highlights

The ionosphere, a crucial component of the space environment, is mainly distributed over the earth at an altitude of 60 to 1000 km
Two polarization SAR (PolSAR) scenes are randomly chosen from the Phased Array L-band Synthetic Aperture Radar (PALSAR) dataset [25]
The total variation (TV) method is able to filter the noise in an image while keeping the sharpness of edges in the

Summary

Introduction

The ionosphere, a crucial component of the space environment, is mainly distributed over the earth at an altitude of 60 to 1000 km. FR error, deteriorates the quality of the scattering matrix and decreases the performance of the polarimetric radar system [1,2]. To address this issue, research on detecting and correcting FR is crucial. The ionospheric sounding based on the PolSAR system is possible if the mechanisms of ionospheric interference are understood and accurately modeled [3,4]. In this way, both Earth observation and ionospheric sounding could be done in one spaceborne SAR mission, reducing the cost

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