New Retrieval Methods and Observing Techniques for Planetary Radio Occultation Experiments

The radio occultation (RO) technique has been utilized since the beginning of space exploration to characterize planetary atmospheres and ionospheres. While the RO technique was conceived in the framework of planetary missions, the emergence of Global Positioning System (GPS) RO for sensing the Earth's atmosphere and its increasingly widespread use in numerical weather prediction has spurred new technical advancements that can be applied to planetary RO experiments to enhance science return. In this presentation, we will discuss the following developments and considerations for future planetary RO experiments: 1) The implementation of novel radio holographic methods which utilize both phase and amplitude data, and are widely used in GPS RO processing for sensing the Earth's moist tropical troposphere. These techniques will be useful for existing Venus RO measurements and in the characterization of other planetary bodies with thick atmospheres. The main advantages of using this approach are higher (sub-Fresnel) vertical resolution atmospheric profiles, the ability of resolving the signal when multi-path interference is present (especially relevant when probing dense atmospheres), and the correct cancellation of the refractive defocusing effect. 2) The potential adoption of an onboard Deep Space Atomic Clock (DSAC-2) as a frequency standard for planetary RO experiments and the effect of its higher frequency stability on atmospheric retrievals, and 3) the modes of operation for future planetary RO experiments (two-way, one-way downlink, one-way uplink and cross-link) along with their capabilities and limitations.