Precise orbit determination is fundamental for extracting scientific results from planetary missions. While gravitational forces dominate spacecraft motion, non-conservative forces such as solar and planetary radiation pressure, and atmospheric drag introduce accelerations that are many orders of magnitude smaller. This thesis develops and evaluates advanced models to extract these minute signatures, with a particular focus on the Mars Reconnaissance Orbiter (MRO). A panel-based spacecraft macro-model, including self-shadowing (SSH), is implemented to compute radiation pressure and aerodynamic forces and is thoroughly compared to the cannonball model. Different gas–surface interaction models (GSIMs) and atmospheric models are compared, and their influence on orbit determination is assessed through parameter estimation using real mission data. The results show that simplified representations, such as the cannonball model, cannot fully capture the variability of non-conservative forces, whereas detailed panel methods improve consistency and reduce residuals. The study highlights the importance of accurate force modelling for planetary mission analysis and provides recommendations for future studies.