This thesis deals with the development of Mars atmosphere model and altimeter sensor model in Matlab/Simulink environment, using both S-Function and Embedded Matlab function technics. They have been integrated in a model-based simulator framework together with guidance, navigation and control (GNC) functions and other sensors, actuators and dynamics models setting up the environmentsuitable for planetary Entry, Descent and Landing simulation. The main objective of the thesis is: to generate a C code from the abovementioned models, using the Real-Time Workshop tool, cross compile it into an executable application for the real-time hardware and download the application into the dSPACE platform, in order to perform simulations with an avionics test bench.