Tomography of Equatorial Ionization Anomaly based on GNSS-InSAR Techniques

Abstract:

Equatorial Ionization Anomaly (EIA) is one of the earliest known effects of space weather. EIA affects satellite navigation technologies such as Global Navigational Satellite System (GNSS) and Synthetic Aperture Radar (SAR), causing degradation in precise positioning applications and poor imaging quality. The ionospheric electron density changes dramatically in the EIA region. Real-time and accurate modeling of three-dimensional (3D) electron density in the ionosphere is important for GNSS navigation and SAR imaging applications. In this paper, we propose to realize a sparse reconstruction of the EIA tomography based on GNSS and InSAR techniques. First of all, a forward model of GNSS / SAR signal propagation in EIA region is established by a three-dimensional ray tracing model. The electromagnetic forward propagation model can simulate the refraction effect of the signal in the ionosphere and calculate the group delay and the slant total electron content (STEC). This forward model has been applied for simulating the GNSS, SAR and Interferometric SAR (InSAR) signals in the EIA region. Secondly, based on the simulation data, a tomography algorithm based on principal component analysis (PCA) and compressive sensing (CS) has been applied for GNSS and SAR signals to achieve 3-D tomography in the EIA region. The reconstructed 3-D electron density image generated from the simulation data by the ionospheric PCA tomography are compared with the input physical ionospheric models. Thirdly, we will also discuss the validation of the combined tomography methods in real GNSS navigation data and the future L-band Interferometric SAR missions. Compared with GNSS signals, SAR has higher spatial resolution, that can be used to retrieve small-scale plasma irregularities. The combined GNSS-InSAR techniques will play an important role for mapping multiple scale ionospheric irregularities for various equatorial scintillations.