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Effect of Atmospheric propagation of Electromagnetic Wave on DInSAR Phase
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1  Indian Institute of Remote Sensing (IIRS), ISRO


Earth’s topography and deformation mapping has become a lot more easier by the use of a geodetic technique popularly known as repeat-pass Synthetic Aperture Radio Detection and Ranging (SAR/RADAR) Interferometry (InSAR). However, the measurements obtained through InSAR are liable to atmospheric errors. Due to refraction, Radar waves which traverse through the atmosphere twice, experience a delay. Troposphere and Ionosphere are the two major layers of the atmosphere that are mainly responsible for this delay in the propagating Radar wave. According to previous studies, water vapor and clouds present in the troposphere and the Total Electron Content (TEC) of the ionosphere are responsible for the additional path delay in the wave. An increase is induced in the observed range due to tropospheric refractivity and path shortenings are observed due to ionospheric electron density. The quality of phase measurement is affected by these atmospheric induced propagation delays and hence errors are introduced in the topography and deformation fields. A three-pass differential interferogram (DInSAR) is generated from two interferograms and the effect of this atmospheric delay is studied on the same. The interferograms are generated from three Advanced Land Observation Satellite (ALOS) carrying Phased Array L-band Synthetic Aperture RADAR (PALSAR) Single Look Complex (SLC) images acquired on the same study area. Atmospheric phase correction is done on the generated DInSAR . The phase error due to the atmosphere may be confused with the displacement component. Unless these errors in phase are not corrected, it is difficult to obtain accurate measurements. Thus, for all practical applications of DInSAR, atmospheric error correction is essential in order to avoid inaccurate erratic height and deformation measurements.

Keywords: DInSAR; TEC; ALOS; Atmospheric delay, Phase Correction