Radio Crosslinks Mission Concept for Venus Atmospheric Structure with High Spatial and Temporal Resolutions

Recent research indicated that volcanic eruptions and seismic events at Venus can cause atmospheric waves that propagate upward through the neutral atmosphere and into the ionosphere. Furthermore, a various measurements have revealed anomalous abundances of sulfuric compounds, e.g., SO2, recognized as a potential indicator of volcanic activity.

Spacecraft radio occultations have been used for six decades to investigate planetary atmospheric structure. This is a powerful remote sensing technique given the challenges of in situ measurements of the Venusian atmosphere. In the traditional experimental configuration, phase-stable radio signals are transmitted from a spacecraft orbiting or flying past a planet and received at a ground station after propagating through the atmosphere. Changes in the phase and/or amplitude are used to infer properties of that atmosphere. This can also be reversed in direction for spacecraft equipped appropriately. For the study of the Earth's atmosphere, the occultation technique was advanced to a constellation of missions using spacecraft-to-spacecraft crosslinks, taking advantage of the GPS constellation. Crosslink radio occultations at Venus could address recent relevant questions by obtaining global data coverage in a significantly short interval and enable repeating measurements to reveal time-variable processes.

This paper presents the Venus Atmospheric Science and Communications Opportunity (VASCO) mission concept to carry out atmospheric occultations utilizing two or more small spacecraft equipped with software-defined radios at two different wavelengths in order to isolate the dispersive effects and decouple the absorption of SO2 from that of H2SO4. Based on simulations, VASCO would produce significantly improved spatial and temporal coverage to monitor the atmosphere for possible volcanic activity via SO2 enhancements and/or gravity wave activity in the retrieved temperature profiles. It would also provide proof-of-concept observations for larger constellations of small spacecraft with crosslinks at other solar system bodies.