I.F. Domnin, D.V. Kotov, L.F. Chernogor

It is necessary to solve the inverse radiophysical problem to estimate the ionospheric plasma parameters by the incoherent scattering technique. In practice, the solution found by comparing the measured autocorrelation function of the incoherently scattered signal with a set of autocorrelation functions pre-calculated for the known plasma parameters. A set of such functions is always limited (as determined by the specified search steps), that leads to additional errors. Autocorrelation functions of the incoherently scattered signal are in a complicated manner (nonlinearly) depends on the parameters of the ionospheric plasma, so it is expedient to consider the features of mentioned errors in more detail. Three criteria to determine optimal search steps values for the ionospheric plasma parameters under real noise conditions and the nonlinear nature of the dependence of the incoherently scattered signal autocorrelation function on the values of the ionospheric plasma parameters are proposed in this paper. The quasi-optimal values of search steps for the ionospheric plasma parameters are found as the result of simulation. Proved, that not enough small values of search steps can lead not only to quantitative errors in estimation of plasma parameters, but also to the systemic distortions of the nature of its spatial and temporal variations.