Karin Ågren, Examensarbete Title: Model Calculations of the Ionosphere of Titan during Eclipse Conditions Abstract: This work is based on data from the Cassini spacecraft and the main aim of it is to model the ionosphere of Titan and compare with data from the sixth flyby - T5. T5 occurred April 16, 2005, and was chosen as it is a nightside pass of the moon. A method by M.H. Rees is used to calculate ionisation rate height profiles. The ionisation rate is dependent on the electron flux, the electron energy, the energy dissipation function, the mass density and the energy loss per ion formation. By looking at the main chemical reactions that take place in Titan's ionosphere we can plot the densities of the ion species. These results are compared with actual data with good agreement. We have showed that magnetospheric impacting electrons alone can account for the observed ionisation during T5.