KEYSTONE: Kythiran Eolian dYnamics from the Surface to the Thermosphere from an Orbital NEtwork (A Venus orbita l mission concept)

We propose a two-component planetary mission concept to answer long-standing questions surrounding the nature of the atmospheric circulation of Venus, specifically the origin and maintenance of the tropospheric Retrograde Zonal Super-rotation (RZS) and the transition to (and from) the ionospheric Subsolar to Antisolar (SSAS) flow. The primary objective of this mission concept is to obtain meteorological measurements with sufficient spatiotemporal coverage and resolution to permit the elucidation of the atmosphere through the application of global general circulation models and mesoscale dynamical models. The primary science tasks of KEYSTONE would be to characterize the four dimensional spatiotemporal variability of key constituents of the Venus atmosphere on a wide range of both spatial resolutions and temporal cadences. In doing so, it would serve as a parallel exercise to that which has been carried out in the elucidation of global and local processes in the Earth's atmosphere; namely, the production and launch of Geostationary Operational Environmental Satellites (GOES), and the Earth Observing System (EOS). The former provides key global and mesoscale dynamical information through he tracking of contrasts (in the most current iteration) at 16 distinct narrow wavelength bands [Schmit et al. 2018]. The latter measures variability in key radiative and chemical components of the Earth atmosphere in an effort to better constrain the roles of radiation, clouds, water vapor, and precipitation; the oceans; greenhouse gases; land-surface hydrology and ecosystem processes; glaciers, sea ice, and ice sheets; ozone and stratospheric chemistry; and natural and anthropogenic aerosols. KEYSTONE would apply the lessons learned from each of these atmosphere-focused missions to achieve what they could not, by flying several hyperspectral imagers with tunable filters covering the full range of wavelengths from the near UV to the thermal infrared that are useful for assessing the global nature of the atmospheric circulation of the Venus atmosphere [Peralta et al. 2017]. In utilizing an imaging system rather than a slit-based spectrometer, the exposure times can be tuned to maximize signal-to-noise of each wavelength observed; and full disk imagery can be obtained simultaneously hence minimizing uncertainties that would have arisen from the motion of the pointing as the data acquisition was ongoing. In utilizing tunable filters, a wider range and greater number of wavelengths -- hence species and/or altitudes -- can be characterized. Hence, tropospheric dynamics and composition can be assessed. Schmit, T. J., Griffith, P., Gunshor, M. M., et al. 2018, Bull. Am. Met. Soc., 98, 681. Peralta, J., Lee, Y. J., McGouldrick, K., et al. 2017, Icarus, 288, 235.