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Three-dimensional ionospheric electron density is an important parameter for characterizing the ionosphere. Synthetic aperture radar (SAR), an advanced earth observation technology, has shown its potential for observing two-dimensional vertical total electron content (VTEC). However, retrieval of three-dimensional electron density is limited by the SAR imaging geometry. To solve this problem, a simple method is proposed to reconstruct the regional three-dimensional electron density by ingesting the SAR-derived VTEC into an international reference ionosphere (IRI) model. The ionospheric global (IG) index is updated by minimizing the difference between the SAR-derived and IRI-derived VTECs. Subsequently, the high-spatial-resolution electron density is reconstructed by exploiting the monotonic relationship between the electron density and the IG index. For assessing the performance of the proposed method, two full-polarimetric advanced land observing satellite (ALOS) images with descending and ascending orbits were acquired to reconstruct the three-dimensional electron density over the Alaska region. Incoherent scattering radar (ISR) electron density was collected from the Poker Flat Incoherent Scatter Radar (PFISR) system to validate the reconstructed electron density. The results show that the standard deviations of the electron density decreased by approximately 30% for the ascending orbit and 19% for the descending orbit when the proposed method was used, thereby illustrating its feasibility.
Zhu et al. (Sat,) studied this question.