Reconstruction of the Image of Ionospheric Electron Density Profile Using Computerized Tomography-A Preliminary Result.

Abstract

Recent development of the technique of computerized tomography has provided a new tool to produce two dimensional (i.e., in a vertical slice) images of electron density structure in the ionosphere by utilizing the data of total electron content (TEC) obtained by trans-ionospheric satellite beacon measurements. In this paper, a preliminary result of our simulation study on the application of three kinds of reconstruction algorithm, (1) the multiplicative algebraic reconstruction technique (MART) as a typical iterative method, (2) a method on the principle of maximum likelihood estimation (MML), and (3) the spline function method (SFM), both as non-iterative method, is briefly described from the viewpoint of comparison with respect to characteristics, merits and disadvantages among the three. It should be noted that (1) MART will be a more reliable method if we can remove its shortcoming, i.e., lack of objectivity in the determination of the end of iteration, and (2) both MML and SFM will become useful, provided that we can solve, what is called, the problem of ill-conditioned matrix in the case of MML, and confirm the effectiveness of any information criterion that prescribes the optimum number of knots and the order of B-spline in the case of SFM.