Planning Radio Technologies for Future Exploration of Planetary Environments and Interiors

For several decades, radio scientists have utilized communications links for scientific studies of planetary bodies. For example, experiments have elucidated the thermal history of the Moon from high resolution gravitational field measurements, unveiled the interiors of Titan, Enceladus, Mercury, Phobos, Vesta and Ceres, providing key evidence for identifying subsurface oceans on icy moons; sounded Titan, Saturn, and Pluto's atmospheres, defined details of the structure of Saturn's rings, and refined models for the atmospheres, surfaces, and interior structure of Mars and Venus. Juno has recently measured the gravitational field of Jupiter to reveal its interior structures and Cassini has completed a distinguished history of radio science discoveries at Saturn. Over the next two decades, significant advances in radio technologies, including one order of magnitude improvement achievable in the accuracy of radio-metric observables and advanced calibration techniques could enable many additional scientific breakthroughs. Future exploration concepts focus on applications of small spacecraft and probes and can include spacecraft constellations for studies of atmospheric dynamics, interior structures, and surface properties. Examples include field tests of radio scattering to determine soil properties, smallsat constellations for dense geographic and temporal atmospheric probing, small science-quality software-defined transponders, miniature ultra-stable oscillators, and advanced radio-metric calibrations, with emphasis on precision ranging at the Deep Space Network.