Radio science investigations with an Uranus orbiter mission

The latest Planetary Science and Astrobiology Decadal Survey selected Uranus Orbiter and Probe (UOP) as the next highest-priority Flagship mission. In this context, radio science investigations can provide a significant contribution to the science objectives of a future mission to the Uranian system, as demonstrated by past missions to Jupiter and Saturn, such as Galileo, Cassini, and Juno. This study provides expected performance of radio science investigations, i.e., gravity, radio occultation, and bistatic experiments.

Regarding gravity science, radiometric tracking data enable precise spacecraft orbit determination and estimation of various dynamical parameters of the Uranian system. The measurements can be obtained via the onboard transponder. We will discuss the expected performance for the retrieval of the gravity parameters of Uranus and its satellites, and the satellite orbits. When the spacecraft will be occulted by Uranus’ atmosphere, the radio link will be affected, allowing us to obtain vertical profiles of its neutral component (temperature-pressure) and ionosphere (electron density). In addition, radio occultations also provide measurements of planetary shape, a constraint on the interior and zonal winds. One-way radio occultations require the presence of an onboard ultra-stable oscillator. If a multi-frequency link is available, the dispersive effects can be isolated, improving ionosphere electron density retrievals. Occultations of the Uranian ring system may also be possible to constrain particle size. In this work, the expected performance on the vertical profiles of the atmosphere of Uranus and its satellites will be discussed. Lastly, bistatic radar observations can provide information about the surface of a target, in terms of roughness, dielectric constant, and porosity. A preliminary assessment of bistatic radar observations of the Uranian moons will be provided.