Abstract
Spaceborne synthetic aperture radar (SAR) imagery is affected by the ionosphere, resulting in distortions of the SAR intensity, phase, and polarization. Although several methods have been proposed to mitigate the ionospheric phase delay of SAR interferometry, the application of them with full-polarimetric SAR interferometry is limited. Based on this background, Faraday rotation (FR)-based methods are used in this study to mitigate the ionospheric phase errors on full-polarimetric SAR interferometry. For a performance test of the selected method, L-band Advanced Land Observation Satellite (ALOS) Phase Array L-band SAR (PALSAR) full-polarimetric SAR images over high-latitude and low-latitude regions are processed. The result shows that most long-wavelength ionospheric phase errors are removed from the original phase after using the FR-based method, where standard deviations of the corrected result have decreased by almost a factor of eight times for the high-latitude region and 28 times for low-latitude region, compared to those of the original phase, demonstrating the efficiency of the method. This result proves that the FR-based method not only can mitigate the ionospheric effect on SAR interferometry, but also can map the high-spatial-resolution vertical total electronic content (VTEC) distribution.
Highlights
Synthetic aperture radar (SAR) imagery has demonstrated its potential in the military and in civilian fields, such as ground deformation observation and computer vision systems [1,2,3,4].a challenge to the SAR imagery, with low-frequency SAR systems, is the influence of the ionosphere
There are a number of studies about ionospheric influences on SAR and SAR interferometry (InSAR), such as ionosphere-induced Faraday rotation (FR) on linearly polarized polarimetric SAR data [9,10,11,12,13], ionosphere-induced interferometric phase errors and azimuth offsets on InSAR measurements [14,15,16], ionospheric effects on simulated P-band SAR imagery [17,18] and comprehensive investigation of this effect on SAR and InSAR [19,20,21,22,23,24]
The linearly polarized signal will experience a rotation of the polarization plane by an angle Ω when it propagates through the ionosphere layer
Summary
Synthetic aperture radar (SAR) imagery has demonstrated its potential in the military and in civilian fields, such as ground deformation observation and computer vision systems [1,2,3,4]. Rosen et al [24] proposed an ionospheric correction method based on a multi-frequency split-spectrum processing technique This method exploited the dispersive nature of radar signals in estimating the ionospheric contribution. Map, and applied this map to correct the ionosphere-induced interferometric phase delay He analyzed the factors which may affect the performance of ionospheric correction on SAR interferometry, including ionospheric condition, underlying SNR, number of looks, and geomagnetic latitude. To address limitations in the current ionospheric correction methods on SAR interferometry, an efficient FR-based method is employed to mitigate the ionospheric errors on full-polarimetric SAR interferometry This method exploits the fact that ionospheric errors on an interferogram can be extracted based on the relationship between FR angles and VTEC (vertical total electronic content).
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