Tomographic reconstruction of the ionosphere over North America with comparisons to ground‐based radar

Abstract

Data collection for the first ground‐based ionospheric tomography campaign in North America was conducted over a 48‐hour period in mid‐November 1991. The data consist of records of ionospheric total electron content (TEC) from a number of passes of the U. S. Navy Navigation Satellite System spacecraft over a chain of ground‐based receiving stations. Data collection and reduction techniques are discussed; these include the determination of absolute TEC from the different phase advances induced by the ionosphere in each component of the dual‐frequency spacecraft signal. The use of tomographic methods to reconstruct ionospheric electron densities over a two‐dimensional (2‐D) region of the Earth's ionosphere at a number of different times is demonstrated. Specifically, two distinct tomographic methods, the algebraic reconstruction technique and a maximum entropy method, are used to mathematically invert the records of TEC. The resulting 2‐D contour “maps” of ionospheric electron density are then compared to similar maps produced by the Millstone Hill incoherent backscatter radar facility located at Westford, Massachusetts. Both qualitative and quantitative measures of agreement among the different reconstructions and the radar maps are presented. The behavior of the ionosphere over the course of the experiment is discussed.

EISCAT verification in the development of ionospheric tomography

“…The experimental results given here illustrate some of the progress made in ionospheric tomography using EISCAT comparisons. It can be noted that comparisons have been published relating tomographic images to observations made using the Millstone Hill radar (Foster et al, 1994;Pakula et al, 1995). Recently, Markkanen et al (1995) have reported a new approach to tomographic inversion in which observations by the EISCAT radar are not used for verification but form an input to the reconstruction process itself.…”

Simulation studies on the tomographic reconstruction of the equatorial and low-latitude ionosphere in the context of the Indian tomography experiment: CRABEX

“…Numerous inversion algorithms/methods and their modifications have been tried out for this purpose and the details are available in the literature. The most conventional ones are the iterative methods, like Algebraic Reconstruction Technique (ART), Multiplicative Algebraic Reconstruction Technique (MART), and Simultaneous Iterative Reconstruction Technique (SIRT) (Andreeva et al, 1992;Censor, 1983;Raymund et al, 1990), as well as the maximum entropy method (Pakula et al, 1995;Fougere, 1995). In these algorithms the iteration begins from a chosen initial profile and proceeds step by step until a given stop criterion is met.…”

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

“…The application was first discussed by Austen et al (1986), with subsequent works, relating to simulation study (Austen et al, 1988;Raymund et al, 1990;Fremouw et al, 1992). Experimental tests of CT have also been carried out by several investigators (Andreeva et al, 1990;Kersley, 1992,1993;Raymund et al, 1993;Pakula et al, 1995). As far as we know, there are few literatures of the ionospheric CT which describe comparison of different kinds of reconstruction algorithms; i.e., either the algebraic reconstruction technique (ART) or multiplicative algebraic reconstruction technique (MART) has been applied in the most cases.…”

“…As far as we know, there are few literatures of the ionospheric CT which describe comparison of different kinds of reconstruction algorithms; i.e., either the algebraic reconstruction technique (ART) or multiplicative algebraic reconstruction technique (MART) has been applied in the most cases. Only exception is Pakula et al (1995) who used two distinct methods, ART and a maximum entropy method, giving both qualitative and quantitative measures of agreement between the two methods.…”