Distortions of the low frequency signal by Martian ionosphere at vertical propagation

A mathematical tool is described that takes into account signal distortions caused by phase dispersion and signal absorption in the Mars ionosphere during reflection from the Mars surface below the orbiter. This tool is used to estimate the distortion of the cross-correlation function by phase dispersion and signal absorption caused during a double traverse of the radio signal through the Mars nighttime ionosphere on frequencies used for the radar experiment MARSIS. Ionospheric absorption reduces the cross-correlation function distortions caused by ionospheric dispersion. It is shown, that the value of signal absorption depends on free electron number density in the lower part of an ionosphere.