Venus Surface and Deep Atmosphere Temperature from Near Infrared Imaging

Kurzfassung

The surface of Venus is close to thermal equilibrium with the atmosphere that it is in contact with due to the high opacity and heat capacity of the atmosphere. Imaging of surface thermal emissions through spectral windows in the near infrared (NIR) is therefore sensitive to the atmospheric temperature structure within the altitude range covered by topography. The deep atmosphere of Venus cannot maintain large lateral temperature gradients due to the efficient redistribution of heat by convection. Accordingly, the Venus International Reference Atmosphere (VIRA) model describes the entire atmosphere below 33 km altitude with a single temperature profile. A major goal of the NIR imaging is to retrieve surface emissivity, requiring a constraint on surface temperature. However, recent works indicate variation not captured in the VIRA model. There is little in-situ data of the near surface atmosphere. The most recent and most highly resolved temperature profile from the VeGa 2 mission in 1985 shows variations in the temperature lapse rate not present in VIRA, which are difficult to explain since they seem to below 7 km altitude. topography affects the atmospheric heat transport via slope winds, resulting in deviations from the VIRA profile below 1 km altitude that vary from region to region. We will present surface temperature data derived from near infrared imaging that show deviations from the VIRA profile similar to those in the GCM, indicating that such data could be used to validate or improve the models. The existing imaging data has low SNR and coverage. We will provide an estimate of the capability of the VEM instrument (NASA VERITAS & ESA EnVision) in terms of equivalent surface temperature uncertainty, and discuss the global coverage. The DAVINCI+ mission will investigate the thermal structure of the lower atmosphere, which is extremely valuable in light of the difficulty in interpreting the VeGa data. A model accurately fitting all these expected data would not only greatly improve our understanding of atmospheric dynamics, but also would enable us to tie information on absolute surface emissivity / reflectance gathered below the bulk of the atmosphere by landers and descent probes to all regions observed by VEM.