Global exploration of the upper atmosphere of Mars using radio occultation measurements

The structure of the upper atmosphere of Mars has long remained poorly known, with only sporadic measurements available until recently, when Nasa's MAVEN and ESA's Mars Express and ExoMars spacecraft visited the planet with the relevant instrumentation to explore regions above 100 km in the atmosphere. The planet's ionosphere was explored using the technique of radio occultations, whereby a radio signal emitted from the spacecraft is traced and measured by the Deep Space Network as the spacecraft disappears behind the planet. This techniques allows vertical profiles of electron densities to be inferred, but by nature of the geometry only the dawn and dusk regions can be sampled, not the dayside and nightside regions which are known to be crucial for our understanding of chemistry and transport processes (winds). To overcome this limitation, ESA recently trialled for the first time ever at Mars spacecraft-to-spacecraft occultations, sampling any region, the dayside and the nightside. The PhD project will consist in exploring this new dataset which will be made available to us and analysed by the PhD student. He will start with a technique he previously developed during his time at ESA and build on that in order to obtain a robust and reliable technique for reducing past and future datasets. Thereby, the student, in addition to having developed a methodology which can be used in future planetary explorations, will obtain a dataset of ionospheric electron densities which can be further investigated for structural anomalies, including the effects of Mars' crustal magnetic fields on ionospheric structures and, by using and further developing chemistry and transport models available in the group, contribute towards identifying the main processes shaping the ionosphere of Mars.