Ionospheric tomography: its limitations and reconstruction methods

Recent modeling and experimental efforts carried out by several research groups indicate that tomographic reconstruction is a promising experimental tool for obtaining images of ionospheric structures. The technique makes use of navigation satellites and a network of ground-based receiving stations which are used to measure the total electron content (TEC) on a number of paths through the ionospheric region of interest. In practice, the available TEC data are inevitably sparse and incomplete and this imposes certain limitations on the reconstructed images. The nature of these limitations is described in this paper. In addition, a unified discussion of some of the various reconstruction algorithms is presented. The difference between the reconstruction methods arises from different choices for the basis functions which are used to represent the unknown electron density structure. Three such choices for the basis functions are discussed. One of these uses the concept of expansion in terms of model ionospheres which can incorporate a priori information about the ionosphere. An example illustrating the application of the method to image the equatorial ionosphere with extremely sparse data is described. The technique is shown to produce an excellent reconstruction for this case which was not well reconstructed using techniques that do not incorporate the a priori information. Finally, the paper is concluded with a short review of experimental work that has been reported in the literature to date.

[1]  J. Klobuchar,et al.  Application of computerized tomography to the investigation of ionospheric structures , 1990 .

[2]  Y. Censor Finite series-expansion reconstruction methods , 1983, Proceedings of the IEEE.

[3]  S. Deans The Radon Transform and Some of Its Applications , 1983 .

[4]  R. Bracewell Strip Integration in Radio Astronomy , 1956 .

[5]  Gene H. Golub,et al.  Matrix computations , 1983 .

[6]  Jeffrey Robert Austen,et al.  Ionospheric imaging using computerized tomography , 1988 .

[7]  Elena S. Andreeva,et al.  RADIOTOMOGRAPHIC RECONSTRUCTION OF IONIZATION DIP IN THE PLASMA NEAR THE EARTH , 1990 .

[8]  Mihail Codrescu,et al.  A fully analytic, low‐ and middle‐latitude ionospheric model , 1989 .

[9]  B. F. Logan,et al.  The Fourier reconstruction of a head section , 1974 .

[10]  E. L. Afraimovich,et al.  Diagnostics of large-scale structures of the high-latitude ionosphere based on tomographic treatment of navigation-satellite signals and of data from ionospheric stations , 1992 .

[11]  K. C. Yeh,et al.  Limitations of ionospheric imaging by tomography , 1991 .

[12]  Hua Lee,et al.  Orthogonal decomposition technique for ionospheric tomography , 1991, Int. J. Imaging Syst. Technol..

[13]  Hua Lee,et al.  Resolution analysis of tomographic reconstruction of electron density profiles in the Ionosphere , 1990, Int. J. Imaging Syst. Technol..

[14]  N. I. Dvinskikh Expansion of ionospheric characteristics fields in empirical orthogonal functions , 1988 .

[15]  James A. Secan,et al.  Application of stochastic inverse theory to ionospheric tomography , 1992 .