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Long-term Studies of the Venusian atmosphere with the Radio Occultation Experiment VeRa on Venus Express

Presentation #502.06 in the session Venus I (Oral Presentation)

Published onOct 23, 2023
Long-term Studies of the Venusian atmosphere with the Radio Occultation Experiment VeRa on Venus Express

The Venus Express Radio Science Experiment VeRa performed regular radio-sounding experiments of the Venus neutral atmosphere using the spacecraft radio subsystem in the one-way radio mode at X-band (8.4 GHz) and S-band (2.3 GHz). The radio link was stabilized by a dedicated onboard ultrastable oscillator. More than 1000 atmospheric profiles could be retrieved between July 2006 and January 2014. Radial profiles of neutral number density from the atmospheric-induced Doppler shift during the occultations cover the altitude range from the upper troposphere (~40 km) to the upper mesosphere (~90 km). These are then used to derive vertical profiles of temperature and pressure.

The spatial coverage of radio occultation measurements is generally quite limited, but the extensive VeRa data set covers almost all latitudes, longitudes and local times. This provides the unique opportunity to study the global atmospheric structure and dynamics at a high vertical resolution.

Small-scale fluctuations in the thermal profiles reveal a significantly enhanced gravity wave activity in the adjacent lower mesosphere with a strong latitudinal gradient.

Global scale wave phenomena can also be retrieved from the data set. Thermal tides are especially pronounced in the low latitudes with a dominating semidiurnal wave structure in the upper mesosphere.

The thermal profiles can also be used to retrieve zonal winds if the assumption of cyclostrophic balance is applied.

The presentation will give a comprehensive overview of the atmospheric scientific results that could be achieved with VeRa in view of the radio occultation studies planned with EnVision and former radio occultation experiments.

The EnVision radio occultation experiment is part of the Radio Science Experiment (RSE) on EnVision. Compared to Venus Express, its much shorter orbit provides the opportunity to study the Venusian atmosphere with an exceptionally good spatial and local time coverage to reveal short-term local atmospheric changes. The use of Ka-band, which has never been used to sense the Venus atmosphere so far, allows (in combination with X-band) to study the H2SO4 absorption in the Venus cloud layer due to its high sensitivity to sulfuric acid absorption in the liquid and gaseous phase.

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