LIMITATIONS OF IONOSPHERIC IMAGING BY TOMOGRAPHY

The potential of imaging large ionospheric structures by applying tomographic techniques has only been proposed recently and has already received interest and increasing attention by workers in ionospheric research. In the combined case of an idealized plane geometry and complete and continuous data extending to +/- infinity the inversion is exact and unique. This is no longer the case if any of the idealized conditions are removed. Specifically, we investigate the limitations arising from limited angles, sampled data of finite receiving aperture and circular geometry. Under these various nonidealized but more realistic conditions, fidelity of the reconstructed image is investigated by computing the response to an impulse source function. The deterioration of the reconstructed image, the sensitivity to the position in the image plane, and the possible existence of ghost images are all numerically investigated and illustrated. Possible methods of improvement are suggested.