This project involves work on force modelling and orbit prediction of Low-Earth Orbiter (LEO) and Medium-Earth Orbiter (MEO) satellites. This includes the modelling of solar radiation pressure and thermal effects on a number of missions including CRYOSAT and JASON-2, as well as research into the influence of the coupling of magnetic field and surface charges on satellite trajectories. This project is funded by the UK's Natural Environment Research Council and involves collaboration with NASA JPL and NASA GSFC.