The Venus oxygen nightglow and density distributions

Observing Venus nightglow is a key tool to understand the composition and the dynamics of its atmosphere. Results deduced from observations can be implemented to produce a data model of Venus atmosphere. For instance, the Visible and Infra-Red Thermal Imaging Spectrometer (VIRTIS) instrument on board the Venus Express spacecraft is very useful to analyze the O2(a1Δ) nightglow at 1.27 µm in the Venus mesosphere. Nadir observations can be used to create a statistical map of the emission on Venus nightside. It appears that the maximum of the emission is located near the antisolar point. Limb observations also provide information on the altitude and on the shape of the emission layer. Combining nadir observations and vertically integrated limb observations improves the statistics of the emission map on Venus nightside. An associated limb profile can also be deduced for any point of the nightside. Given all these O2(a1Δ) intensity profiles, O2* density profiles can be calculated. O density profiles can also be calculated as long as CO2 density profiles are available. These can be retrieved either from the VTS3 model or from SPICAV stellar occultation measurements. Finally, three-dimensional maps of excited molecular and atomic oxygen densities can be generated. The oxygen density map shows significant differences from the VTS3 model predictions.