Reanalysis of the Voyager 2 radio science experiment in Uranus (1986)

This MSc thesis presents a reanalysis of the Voyager 2 radio occultation experiment on Uranus, focusing on the impact of considering different wind models, thermal noise, and atmospheric composition on the pressure-temperature profiles. The radio science experiment was conducted in January 1986, and it provided frequency data in S-Band and X-Band, which have been processed to derive Doppler residuals, refractivity profiles, and finally pressure-temperature profiles for the equatorial regions near the Southern Hemisphere. The data analysis has been performed with the help of a modern ray tracing code developed by the University of Bologna. The influence of thermal noise was quantified, revealing uncertainties of ± 5 K and ± 0.2 mbar restricted to the 0.3–3 mbar region. Initial condition uncertainties also contributed up to ± 5 K in the upper atmospheric layers. Variations in wind models led to temperature uncertainties as high as ± 30 K at 0.5 mbar, of around 5 K at 10 mbar, and of around 1 K at 100 mbar. These data can support the hypothesis of seasonal wind variations. Methane, omitted in earlier analyses, was found to induce significant warming ranging from 0 K to almost 3 K in the pressure interval of interest, revealing the importance of including minor species in future studies. This work illustrates a method for estimating uncertainties in Uranus’ atmospheric profiles and corroborates the importance of seasonal and composition effects. While the results support the seasonal variation hypothesis, more data and advanced techniques, such as Monte Carlo simulations, are required for further refinement.