Scientific and instrumental requirements for VIS/IR studies of Venusian atmosphere from the upper cloud level down to the surface in the light of future space missions

Abstract

Venus is one of the less well studied planets in the inner solar system. Despite its mass being comparable to that of Earth, the development of its environmental conditions followed a completely different evolutionary path. Today s dense CO2 dominated atmosphere is characterized by extreme surface conditions of 92 bar and 735 K at the mean altitude of the planet s surface and a cloud layer enriched with sulfuric acid aerosols, which makes observations of the daytime surface in the visual spectral range impossible. This circumstance led to a long standstill for further space programs to Venus after the first space-based explorations of this planet in the 1970s through the mid-1990s, which was not broken until the launch of ESA s Venus Express (VEX) mission in 2005. Missions such as VEX, Akatsuki (JAXA), and BepiColombo (ESA; MERTIS, first Venus flyby) have made new VIS-IR spectroscopic measurements of Venus in recent years, contributing to the study of its atmosphere and surface. We report here selected results of these investigations and their comparison with earlier data. We derive from these discussion scientific and instrumental requirements for VIS-IR spectroscopic spaceborne measurements with focus to currently selected and future space missions such as EnVision (ESA) and VERITAS (NASA), and discuss their capabilities and limitations for atmospheric and surface studies.