X-band scintillations in Venus radio occultations observed by Akatsuki

Abstract

Power fluctuations are observed on radio signals propagating through the Venus atmosphere. These scintillations, due to fluctuations in refractive index, are particularly strong between 56 and 72 km altitude where the strong convective stability favors gravity wave propagation. We examine low-latitude X-band radio occultation experiments performed by the Akatsuki spacecraft to assess the statistical variability of these scintillations. The observed root-mean-square scintillation amplitudes at a given altitude vary by a factor of about 3. Part of this range is due to the different geometry of the occultations: the corresponding variations in refractive structure constant at 60-70 km altitude span a factor of ∼2. These propagation characteristics may influence the optimization of the two-way radio link for the DAVINCI mission currently in development.