William POLYCARPE

Elaboration, implementation and testing of softwares for CNES and ESA - Space Surveillance and Situation Awareness: implementation of a O(n) algorithm for conjunction filtering (Cube, FilteringLib, Java,cluster computing) - Flight Dynamics : implementation of semi-analytic models for satellite orbit/attitude propagation (SAAP/ESA, Godot, Orekit, C++, Matlab, Julia) . Talk at Godot Community Workshop 2023. - Software maintenance : Orbit determination, manoeuvres and Data Statistics (ZOOM, Lotus, Patrius, Astreo, Java, Python, Panda, Git) - Internship supervision

- Functional testing for conjunction filtering (FilteringLib, Java, cluster computing) - Maintenance of Flight Dynamics library (BIBOR, Java, SVN) : Orbit determination, trajectory optimisation

Parallel to my PhD work, I was also selected to work as an outreach speaker at the Palais de la Découverte, which is a major and popular science museum in Paris. My activities consisted of giving presentations on the subject of gravitation and General Relativity. The public particularly enjoyed the part on astronauts and gravitational waves detection. Furthermore, along with fellow colleagues, we organised a week of meetings with the public, where we explained the lives and work of researchers. During this time, I also enjoyed presenting my own work on the moons of Saturn. Finally, I have written an article on the subject of tidal heating and water inside planetary moons for the outreach journal "Découverte". It will be published in the Edition 427 in Mars-April 2020.

- Numerical Integration of Equations of motion (Fortran) - Semi-analytical methods for long term N-Body propagation (Mathematica) - Astronomical Observations (NEO objects) - Peer review publication The subject of my PhD was the orbital dynamics of the moons around Saturn. It was observed that the moons are migrating outwards at a fast rate due to strong tidal dissipation in the convective areas of Saturn's interior. Many features of Saturn's evolution have to be studied in this framework. Many past mean motion resonances may have played an important role in the shaping of the whole system, such as the past 5:1 resonance between Titan and Iapetus. This resonance could be the key to explain Iapetus' eccentric and tilted orbit. My work consisted of running numerical simulations of this past resonance by using a N-Body integrator, which I developed myself, and using a semi-analytic code which I produced by performing an expansion of the equations of motion. The results suggest that the resonance could be a plausible explanation for Iapetus' orbit and simulations show that there are constraints on the migration rate of Titan. I was awarded a prize for a poster I presented at a conference specialised in Celestial Mechanics (CELMEC VII) and my work is published in the peer-reviewed journal Astronomy and Astrophysics. The title of my thesis is "Study of a recent 5-1 mean motion resonance between Titan and Iapetus" and is available online here https://theses.hal.science/tel-02104031v1

I was teaching mainly Mathematics and Physics at all levels between primary school and first year university students.

Implementation of an Initial Orbit Determination algorithm for laser ranging data. To goal was to write a Fortran code from a paper which outlines the theory and test the algorithm on several examples.