Improved Computerized Ionospheric Tomography Based on GPS and PALSAR Data

Due to factors such as the uneven distribution of ground receiving stations and the lack of effective observation rays, Global Positioning System (GPS)-based computerized ionospheric tomography (CIT) is typically of low quality and requires additional data sources. Recently, Faraday rotation angle (FRA) retrieval using the Phased Array L-band Synthetic Aperture Radar (PALSAR) full-pol data have emerged as a reliable technique for ionospheric detection. Similar to the total electron content (TEC), the FRA is the integral effect of the electron density and geomagnetic field, with the geomagnetic field being accurately estimated by the International Geomagnetic Reference Field (IGRF) model. Therefore, this paper proposes a 3-D secondary CIT algorithm by integrating PALSAR and GPS data: first, the product of the electron density values obtained from GPS-based CIT and the magnitude of geomagnetic field in corresponding voxel obtained from IGRF is used as the initial value. Then, the iterative algorithm is improved by using the FRA obtained from PALSAR data, rather than TEC, as the input for the second iteration, avoiding the approximation error caused by converting FRA into TEC. The geomagnetic field information is then separated by using the IGRF model, and the reconstructed spatial distribution is finally obtained. Experimental verification shows that the FRA can compensate for the lack of GPS observation rays to a certain extent and improve the accuracy of the reconstructed electron density. The results also indicate that the PALSAR can provide an effective and feasible data source for CIT.