Measures of information content for computerized ionospheric tomography

Computerized ionospheric tomography (CIT) is an emerging technique that produces two-dimensional images of electron distributions in the ionosphere. The limiting factor for the reconstruction of these images using computerized tomographic techniques is the inability to accurately estimate their vertical profiles. This is due to the geometry of CIT systems which limits the amount of information detected at large projection satellite angles. A relationship exists between the amount of orbit information that is gathered at a particular projection angle, and the positions of the ground station receivers. Therefore, the proper placement of the ground station ionosphere receivers can increase the information content of the dataset, and consequently increase the resolution of resulting images. In order to measure the effect of varying the placement of the ground station receivers, a resolution metric is needed. This paper presents a resolution measure based on projections that enables observation of information content as a function of ray path angle. This resolution measure enables the development of optimal systems as well as evaluation of existing system configurations