Limited Angle Tomography Using Volumetric Constraints

Earth with 4 station receiver chain The ionosphere lies approximately in the 80 — 500 km altitude range. As the satellite passes over head it sends dual frequency radio signals at 150 and 400 MHz respectively which undergo different amounts of Doppler phase shift along each ray path before they are simultaneously received by the ground stations. The difference of Doppler shift encountered by each received signal sample is subsequently processed to obtain information about the total electron content (TEC) of the ionosphere along the corresponding ray path. TEC records for parallel ray paths are grouped together as samples of pseudo tomographic projections, and used to reconstruct the ionospheric plane electron distribution with the aid of different tomographic image reconstruction algorithms [3,4,5]. The result of missing horizontal rays is that reconstructions lack considerable distribution information in altitudinal direction [6]. Hence, it is difficult to locate absolute heights of important electron formations such as peaks and troughs [2] as shown in Figure 2.