Analysis of NASA’s DSN Venus Express radio occultation data for year 2014

The Venus Express Radio Science Experiment (VeRa) was part of the scientific payload of the Venus Express (VEX) spacecraft and wastargeted at the investigation of Venus’ atmosphere, surface, and gravity field as well as the interplanetary medium. This paper describes themethods and the required calibrations applied to VEX-VeRa raw radio occultation selected data used to retrieve vertical profiles of Venus’ionosphere and neutral atmosphere. In this work we perform an independent analysis of a set of 25 VEX, single-frequency (X-band), occultationscarried out in 2014, recorded in open-loop at the NASA Deep Space Network. The calibrations are performed to correct the observed frequencyfor the major noise sources and errors, since any uncalibrated eects will bias the retrieval of atmospheric properties. We present a study on theinfluence of the relativistic eects on radio occultation of Venus. The temperature dierences between the relativistic and non-relativistic Dopplershift solutions are lower than 0.5 K at 50 km altitude, and our error analysis shows that, within this investigation, the relativity eects can safelybe neglected. Our temperature, pressure and electron density vertical profiles are in agreement with previous studies available in the literature.Furthermore, our analysis shows that Venus’ ionosphere is more influenced by the day/night condition than the latitude variations, while theneutral atmosphere experiences the opposite. Our scientific interpretation of these results is based on two major responsible eects: Venus’ highthermal inertia and the zonal winds. Their presence within Venus’ neutral atmosphere determine why in these regions a latitude dependence ispredominant on the day/night condition. On the contrary, at higher altitudes the two aforementioned eects are less important or null, and Venus’ionosphere shows higher electron density peaks in the probed day-time occultations, regardless of the latitude.