Robust Computerized Ionospheric Tomography Based on Spaceborne Polarimetric SAR Data

摘要

Due to the dispersion nature of the ionosphere, the spaceborne polarimetric synthetic aperture radar (PolSAR) systems at L or lower frequencies will generally experience more severe effects in comparison to frequencies above L-band. Correspondingly, according to the mechanism of how ionosphere destroys the scattering matrix of PolSAR data, the total electron content (TEC), an important input in computerized ionospheric tomography (CIT), can be retrieved by model inversion. Thus, this paper presents a technique of CIT based on the spaceborne PolSAR data. The CIT technique is a means to obtain the spatial distribution of ionospheric electron density from the TEC values. Because of the high spatial resolution of spaceborne SAR, the kilometer-scale TEC information can be obtained by the PolSAR data where such resolution was previously inaccessible. The spatial distribution of ionospheric electron density with high resolution can therefore be obtained. In addition, the potential limitation of previous CIT based on SAR imaging information is the difficulty in requiring strong point targets with high signal-to-clutter (SCR) ratio in scenes. In contrast, the CIT reconstruction based on scattering matrix information can be easily realized without aforementioned special requirements. In this paper, by using the simulated data of the Advanced Land Observing Satellite (ALOS) Phased-Array L-band Synthetic Aperture Radar (PALSAR) full-pol data, the International Reference Ionosphere (IRI) 2007, and the International Geomagnetic Reference Field (IGRF) models, the reconstruction of ionospheric electron density distribution is first simulated to validate the feasibility of the proposed technique. Then, possible effects of SAR system and model errors on the reconstruction results are also simulated and analyzed to show the applicability.