Journal ArticleDOI
Resolution degradation parameters of ionospheric tomography
Helen R. Na,Hua Lee +1 more
Reads0
Chats0
TLDR
In this article, a method of evaluating sampling schemes to measure the information content of the resulting projections is presented, and a relationship between the angular reindexing error and the point spread function of the imaging system is derived.Abstract:
Tomographie reconstruction of the electron density structure in the ionosphere has generated much interest due to the possibility of high-resolution two-dimensional image reconstruction using total electron content (TEC) data. An algorithm based upon the filtered backprojection algorithm of X ray tomography that provides such two-dimensional reconstructions has been developed; however, the resolving capability is limited by the nature of the ionospheric system. In ionospheric tomography, each piece of data contains information similar to a sample on a projection in X ray tomography. Collectively, however, the information content of ionospheric data sets is significantly different from a set of tomographic projections. These differences are the result of characteristics of the data acquisition system and are directly related to the resolution limits of the reconstructed images. In this paper the data acquisition system is analyzed to determine the sources of this degradation. Two key parameters of nonuniform sample spacing and angular reindexing error are analyzed to determine their effect upon the reconstruction process. A method of evaluating sampling schemes to measure the information content of the resulting projections is presented. Finally, a relationship between the angular reindexing error and the point spread function of the imaging system is derived.read more
Citations
More filters
Journal ArticleDOI
Ionospheric radio tomography using maximum entropy 1. Theory and simulation studies
TL;DR: In this article, a linear combination of orthonormalized simple Chapman profiles is used to extract the required vertical profile for three different test cases, as follows: an arbitrary vertical profile is assumed; for convenience, the coefficients of these functions are found using a nonlinear optimization procedure in conjunction with repeated MaxEnt calculations.
Journal ArticleDOI
Investigations of the ionosphere by satellite radiotomography
TL;DR: An overview of tomographic approach to remote sensing of ionosphere by radio waves is presented, including diffraction, statistical, and ray radiotomography, and results from satellite experiments in 1984–1993 are shown demonstrating the great possibilities of the radiotOMographic method in ionospheric research.
Journal ArticleDOI
Application of generalized singular value decomposition to ionospheric tomography
TL;DR: In this paper, the electron density distribution of the low and mid-latitude ionosphere has been investigated by the com- puterized tomography technique using a Generalized Singu- lar Value Decomposition (GSVD) based algorithm.
Journal ArticleDOI
Ionospheric tomography using the residual correction method
Eric K. Sutton,Helen Na +1 more
TL;DR: The residual correction method (RCM) as discussed by the authors is a fast, efficient, and numerically stable ionospheric tomography algorithm, which uses an existing technique called orthogonal decomposition.
Journal ArticleDOI
Comparison of geometries for ionospheric tomography
Eric K. Sutton,Helen Na +1 more
TL;DR: The orthogonal decomposition (OC) algorithm as mentioned in this paper provides a theoretical framework that unifies several traditional tomographic reconstruction algorithms, depending upon the choice of basis functions for the image domain.
References
More filters
Journal ArticleDOI
Ionospheric imaging using computerized tomography
TL;DR: In this paper, the authors formulated the CT problem as it applies to ionospheric imaging and investigated the limitations of the CT technique in the presence of multiple ground stations, assuming a 1000km-altitude polar-orbiting satellite and both five and three ground stations.
Journal ArticleDOI
Application of computerized tomography to the investigation of ionospheric structures
TL;DR: In this paper, a method for approximating the peak height and scale height of the electron density profile is discussed as well as a reconstruction technique based on the multiplicative algebraic reconstruction technique algorithm and a back projection based initial guess.
Journal ArticleDOI
Application of stochastic inverse theory to ionospheric tomography
TL;DR: In this paper, the authors apply the weighted, damped, least squares (WDS) technique of stochastic inversion to two simulated but realistic data sets, which is particularly suited to solving inverse problems in geophysics because it provides an orderly mechanism for judicious use of a priori or external information to complement sparse or nonuniform path integral data.
Journal ArticleDOI
Limitations of ionospheric imaging by tomography
K. C. Yeh,T. D. Raymund +1 more
TL;DR: In this paper, the authors investigated the fidelity of the reconstructed image by computing the response to an impulse-source function under various non-idealized but more realistic conditions, such as finite receiving aperture and circular geometry.
Journal ArticleDOI
The determination of ionospheric electron content and distribution from satellite observations: 2. Results of the analysis
TL;DR: In this article, the results of observations of the radio transmissions from Sputnik III (1958δ2) in an 8-month period are presented, revealing the diurnal variation of the total ionospheric electron content; also, the ratio of the overall content to the lower ionosphere below the height of maximum density in the F layer is obtained.