Reformulating the Split-Spectrum Method to Facilitate the Estimation and Compensation of the Ionospheric Phase in SAR Interferograms

Abstract

Spatial and temporal variation of the free electron concentration in the ionosphere affects SAR interferograms, in particular at low radar frequencies. The split-spectrum method permits separating the ionospheric and the non-dispersive phase terms using spectral sub-band images. In this work a reformulation of the split-spectrum method facilitates the necessary processing steps. Reformulating the split-spectrum method permits determining the ionospheric phase component based on a split-spectrum double-difference interferogram and the full-bandwidth differential interferogram. In this way differing a pair of unwrapped phase images, each one scaled by a large factor, can be avoided, making the method more robust. The applicability of the proposed method is demonstrated with examples including cases with very strong ionospheric effects.