Ionospheric tomography is a method of obtaining information about the ionosphere that has been studied extensively in the past few years. The data used for ionospheric tomography consist of measurements of Total Electron Content (TEC) between several ground stations and an orbiting satellite. Since TEC is the integral of electron density, computerized tomography techniques can be used to reconstruct an image of ionospheric electron density in the vertical plane between the ground stations and satellite orbit. Several recent studies have demonstrated the feasibility of this technique [1,2].
There are several limitations associated with ionospheric tomography systems. Since all data are collected between the satellite orbit and ground, an ionospheric tomography system is approximately analogous to a limited angle tomography system. In particular, ionospheric tomography systems have problems with both limited view angle and missing data. Due to these problems, ionospheric tomography systems exhibit extremely poor vertical resolution [3,4,5]. Some form of a priori information must be used in the reconstruction algorithm to obtain a useful reconstruction. There exist several sources of a priori information on the vertical profile of ionospheric electron density, such as ionospheric models and ionosonde measurements.