An Improvement of Ionospheric Phase Correction by Multiple-Aperture Interferometry

Abstract

Recently a multiple-aperture interferometry (MAI)-based azimuth shift method has been proposed to correct the ionospheric phase on synthetic aperture radar (SAR) interferograms. This method needs to determine integral constants required for azimuth integration. The exact estimation of the integral constants plays a key role in this MAI-based method. In this paper, we propose an efficient method for improving the performance of integral constant estimation, which functions by simultaneously removing the ionospheric and orbital phase artifacts from the interferometric SAR interferogram. We validate the performance improvement of the proposed method using two Advanced Land Observation Satellite Phase Array L-band SAR (ALOS PALSAR) interferometric pairs. The proposed method is compared with a MAI-based method, which does not work well due to azimuth integration errors. The proposed method successfully corrects the ionospheric and orbital phase artifacts. In addition, we compare the performances of the previous and proposed methods using the in situ Global Positioning System velocities. The root-mean-square error (RMSE) in line-of sight velocity from the previous method is about 7.0 mm/yr, whereas the RMSE from the proposed method is about 4.3 mm/yr. An RMSE reduction of about 38.6% is achieved when using the proposed method. These results indicate: 1) that the proposed method successfully estimates and corrects the ionosphere and orbital phase distortions; and 2) that the proposed method is superior to the previous method. Index Terms-Advanced Land Observation Satellite (ALOS)Phase Array L-band SAR (PALSAR), ionospheric phase correction, multiple-aperture interferometry (MAI), orbital phase correction, SAR interferometry (InSAR), synthetic aperture radar (SAR).

Three‐dimensional deformation mapping of a dike intrusion event in Sakurajima in 2015 by exploiting the right‐ and left‐looking ALOS‐2 InSAR

“…We also computed the azimuth displacement (dAZ), A = [ a 1 , a 2 , a 3 , a 4 ] T , by MAI [ Bechor and Zebker , ; Jung et al , ]. No significant deformation signal has been detected in the dAZs because they contain very large noises possibly due to ionospheric disturbances [ Jung et al ., ; Jung and Lee , ] (supporting information Figure S8). Standard deviations of the dAZs ( ) were also calculated using equation , which are a few dozen times larger than (Table and supporting information Figure S8).…”

The Multiple Aperture SAR Interferometry (MAI) Technique for the Detection of Large Ground Displacement Dynamics: An Overview

“…Generally, high TEC and low RADAR frequencies cause significant ionospheric artefacts. In this framework, new MAI-based ionospheric correction techniques have very recently been proposed [83][84][85][86] to correct the InSAR phase. These techniques exploit the fact that the azimuth derivative of the ionospheric phase distortion on RADAR interferograms is linearly proportional to the apparent pixel azimuth displacement ∆x:…”

“…In Figure 7a [83] have presented a more-efficient ionospheric correction method that improves the performance of the aforementioned work by using a multivariate regression method [84] to correct both ionospheric and orbital artefacts. Finally, Fatthai et al [86] very recently proposed an algorithm based on the use of the MAI technique for the time-series estimation of ionospheric phase delay from a stack of SAR acquisitions.…”

Measurement of small co-seismic deformation field from multi-temporal SAR interferometry: application to the 19 September 2004 Huntoon Valley earthquake

“…In the atmospheric layers, ionospheric effect can be negligible when using short-wavelength radar signals because the effect is inversely proportional to the radar frequency (Jung et al 2013;Liu et al 2014;Jung & Lee 2015). In contrast, the tropospheric effect is independent of wavelength, and is mainly caused by refractive index changes due to tropospheric conditions, such as the atmospheric water vapour, pressure and temperature.…”