Computerized Ionospheric Tomography And Ionospheric Occultation Inversion Technique

Computerized Ionospheric Tomography (CIT), which is an application of computerized tomography to ionospheric sounding, is suitable for monitoring large-scale spatial structure and disturbance of ionospheric electron density. Using CIT, distribution inversion of ionospheric electron density is studied in this paper. The main topics in this dissertation are summarized as follows:1. CIT of ionosphere theory is discussed systematically, which emphased on inversion algorithm and inversion error, and a new hybrid inversion algorithm is proposed to reconstruct distribution of ionospheric electron density.2. With empirical model of the ionosphere-International Reference Ionosphere (IRI2001), MART algorithm and the presented inversion algorithm in this dissertation are simulated for CIT. From the comparisons of results by the two algorithms, it is indicated that the new inversion algorithm, to a certain extent, can improve the quality of the reconstruction of CIT.3. The images of ionospheric electron density are reconstructed from TEC data, which come from IGS(International GPS Service). And variations of ionospheric parameters with latitude, height, and time are analyzed. In addition, a comparison of reconstructed image from CIT and the results obtained by ionosonde is given.4. The ionosphere inversion technique of occultation data is described. And with two-dimensional ray-tracing program, the simulation of the trace of GPS-LEO occultation is presented.