Profiles of the Venusian ionosphere and neutral atmosphere derived from reprocessed Pioneer Venus radio occultation measurements

The radio occultation technique is a powerful tool to probe the vertical structure and composition of Venus' atmosphere. By measuring the bending and attenuation of radio waves as they pass through the planet's ionosphere and neutral atmosphere, radio occultation allows to derive valuable information about temperature, pressure, density, and amount of sulfuric acid vapor and sulfur dioxide in the Venusian atmosphere. It has been employed to probe the vertical structure and composition of Venus' atmosphere since the 1960s. First measurements were carried out in 1967 with the Mariner V spacecraft. Two measurements were performed at the equatorial day side and nightside. Later, the Mariner 10 flyby on Venus in 1974 was used to conduct one radio occultation measurement at the equatorial region. In the 1970s and 1980s, the Venera spacecrafts have provided ionospheric and neutral atmospheric profiles. The first extended study covering a wide range of latitudes was performed with the Pioneer Venus Orbiter (PVO) mission between the years 1978 and 1992. The ionosphere and neutral atmosphere were sounded with X- and S-band radio waves using a 1.09-m High Gain Antenna. We have recalculated the atmospheric profiles from the PVO mission. The basis for the recalculation formed an improved reconstructed orbit of PVO. We present and discuss the ionospheric and neutral atmospheric profiles reconstructed from the Pioneer Venus mission. Further, we compare the profiles with the original PVO results and with atmospheric profiles derived from other radio occultation studies at Venus.