Analysis and Application of Cloud-Top Winds and UV Features on Venus

Abstract

We present two studies of Venusian dynamics. The first study focuses on measuring Venus' cloud-top winds. Past research has shown an increase in superrotation speed during Venus Express. This change is not fully understood and has not been explored sufficiently to account for its variation with local time, longitude, or observational geometry to constrain dynamical models or to exclude the possibility that it is an artifact of observational sampling biases. We conduct image pair matching and digital CIV-based (Correlation Image Velocimetry) cloud-tracking to measure ~11 million wind vectors. We analyze this extensive data for shifts in observational coverage of local time, longitude, and observational angles; we control for such shifts and find the trend of increasing zonal wind speeds during Venus Express is statistically significant and exists across all local times, longitudes, and emission angles. Therefore, the trend is not due to observational biases. We also find the longitudinal structure significantly changes during Venus Express.

The other study focuses on the concept of an autonomous, vertically-variable, balloon-based aerobot mission to Venus' cloud layer. We simulate the mission's autonomous path planning by implementing an RRT path-planning algorithm. We present an estimated background wind field covering all local time and the enhanced altitude range of 40–65 km. This wind field updates to "inform" the aerobot of its surroundings. Through the RRT (Rapidly-exploring Random Trees) algorithm, the aerobot searches for a path to a given goal region. We found it to be very possible for such an aerobot to successfully passively navigate with Venus' winds by only changing its altitude. We show it can travel equatorward (opposite strongest prevailing meridional winds) and circumnavigate Venus multiple times within a nominal 30-Earth-day mission.