In the paper, an original approach to the formationof the initial approximation in the ionospheric tomography problem with inter-satellite registration of total electron content is presented. The direct Radon transform of the electron density (ED)’s orbital profile is proposed to approximate using convolution of the function of latitudinal distribution of ED’s maximum in the profile with the kernel function. This approximation makes it possible to estimate the latitude distribution of the ED maximum from the total electron content measurements by the deconvolution procedure. An analytical expression of the convolution kernel was obtained. Based on the proposed approach, two variants of formation of the initial approximation which used different prior information, namely, on the solar activity index and on the height of the ionization maximum in the profile, were considered. An accuracy of the mentioned formation was analyzed by the results of statistical simulation, and it was compared with the previously known approach where both the height of the ionization maximum in the profile and ED at this height were known.