Jupiter's atmosphere through Juno's radio occultation experiments

On July 31st, 2023 and September 9th, 2023, Juno performed the first studies of Jupiters atmosphere through radio occultation experiments since the Voyager and Galileo missions. These remote sensing experiments were conducted in a coherent two-way mode, where an uplink signal frequency was used as a reference for the downlink signals, at X and Ka band, transmitted back to the Earth. During these experiments, the geometry of Juno's trajectory was such that the spacecraft was occulted by Jupiter as seen from Earth, therefore the radio signal, transmitted by the probe towards the DSN station, travelled through both Jupiters atmosphere and ionosphere. As a result, the radio signal underwent a phase shift due to the effect of refraction. Therefore, the Earth's antenna recorded a signal with a frequency different from what would have been observed if the signal had propagated through a vacuum. This difference, called Doppler residual frequency, has been used to infer the density, pressure, and temperature profiles of Jupiters neutral atmosphere and the electron number density of its ionosphere. In the analysis of Jupiters atmosphere and ionosphere, where the assumption of spherical symmetry does not hold, the effect of oblateness cannot be neglected. Consequently, the radio data analysis cannot be performed by resorting to the traditional application of the Abel transform. Instead, a more suitable approach involves employing the ray-tracing technique. This technique, based on the geometrical optics approximation, can also take into account the effects of zonal winds in retrieving the properties of Jupiter's atmosphere. Additionally, the use of multi-frequency link techniques allowed us to disentangle the contributions from dispersive and neutral media in the frequency shift. This study presents an analysis of the data collected during the inaugural Juno radio occultation experiments of Jupiter. Specialized software has been developed to analyse the data acquired from these Juno-Jupiter two-way radio occultation experiments. Preliminary results of this analysis are given in terms of ionospheric electron density and atmospheric pressure-temperature profiles.