  The radio signal transmitted by the Mars Express (MEX) spacecraft was
observed regularly between the years 2013-2020 at X-band (8.42 GHz) using the
European Very Long Baseline Interferometry (EVN) network and University of
Tasmania's telescopes. We present a method to describe the solar wind
parameters by quantifying the effects of plasma on our radio signal. In doing
so, we identify all the uncompensated effects on the radio signal and see which
coronal processes drive them. From a technical standpoint, quantifying the
effect of the plasma on the radio signal helps phase referencing for precision
spacecraft tracking. The phase fluctuation of the signal was determined for
Mars' orbit for solar elongation angles from 0 - 180 deg. The calculated phase
residuals allow determination of the phase power spectrum. The total electron
content (TEC) of the solar plasma along the line of sight is calculated by
removing effects from mechanical and ionospheric noises. The spectral index was
determined as $-2.43 \pm 0.11$ which is in agreement with Kolomogorov's
turbulence. The theoretical models are consistent with observations at lower
solar elongations however at higher solar elongation ($>$160 deg) we see the
observed values to be higher. This can be caused when the uplink and downlink
signals are positively correlated as a result of passing through identical
plasma sheets.
