The exploration of the Venus and Jupiter atmospheres by radio occultations: Extending our understanding of the planetary atmospheres beyond Fresnel scale resolution and spherical symmetry

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Current and future spacecraft missions will soon provide new opportunities for the scientific exploration of the atmospheres of Jupiter and Venus. The orbit of the extended Juno mission (2023-2025) eventually provides opportunities for Jupiter radio occultations. JUICE (launch planned for 2023) will explore Jupiter, its ring system, and the Galilean moons by radio science, while the new decade of Venus exploration will begin with two NASA missions (VERITAS: launch ~2028, DAVINCI, launch ~2029) and the ESA EnVision (launch ~2031) spacecraft. The Rheinisches Institut für Umweltforschung (RIU) is in leading position for the radio occultation part of both the EnVision mission at Venus and the JUICE mission at Jupiter. Crucial for the success of the atmospheric radio sounding are reliable prediction and data processing tools, but most important, a sound observation database from previous missions. The objectives of this proposal are: 1.) A 2D/3D forward raytracing software package shall be developed for the prediction and simulation of radio occultations in the non-spherical symmetric atmospheres of Venus and Jupiter. The raytracing software shall be used to analyze the effect of the Venus terminator on the Venus Express VeRa radio occultation data set (~1,000 observations), where atmospheric conditions change over short spatial scales and deviate from the local spherical symmetry assumed during data processing at RIU. The raytracing results shall be integrated in the Venus Express VeRa radio occultation data set and will lead to improved observations at the Venus terminator. The raytracing software shall also be used to study how the oblate Jovian atmosphere and the highly variable ionosphere affect radio occultation observations at Jupiter based on Galileo and the potential future Juno radio occultations. 2.) An upgrade of the currently used radio science data processing method at RIU shall be applied to increase the vertical resolution of the Venus Express VeRa atmospheric profiles to sub-Fresnel scales and remove the bias of multipath propagation effects from the data set. Multipath propagation effects occur also in the Jovian atmosphere and shall also be investigated and removed from the ionospheric Galileo radio science observations and the potential Juno occultations for Jupiter. 3.): The interpretation of the new information about sub-Fresnel scale atmospheric features and the effect of non-spherical symmetric atmospheres on radio occultations shall provide improved knowledge about atmospheric processes, a sound data base for the prediction of future radio science observation, they shall support atmospheric modeling efforts and advance the preparation for the EnVision mission to Venus and the JUICE mission to Jupiter.