The goal of the thermal control of a spacecraft is to keep temperatures and thermal gradients of all its components betveen stated limits. These limits determine the optimum operational conditions for all spacecraft environmental mission phases. To simulate the thermal behaviour of the spacecraft in its environment, a representative mathematical model must be defined.This paper presents the software suite “Logiciel Cannes” - a consistent package of interconnected software using a common data base file and allowing fast and efficient spacecraft modelization.The individual software elements and the unique numerical methods used are presented. The first section concerns the geometric modelization. This is realized with interactive software (CAD type) adjusted to quadrilateral plane surfaces. This geometry is used to compute the view factors, internal radiative exchanges and for the calculation of external fluxes (solar, albedo and earth shine). The second part concerns the conductive exchanges with the particular case of platforms containing active components. An original method of reducing the resulting conductive model is presented. The last part concerns the temperature calculation and the different available tools that allow the checking of intermediate and final results (visualization of orbit and spacecraft configuration, external fluxes, temperatures, thermal fluxes and coatings with respect to the geometry).To end the presentation and to show the efficiency of the “Logiciel Cannes” software suite, some comparisons concerning CPU time with other established software packages are shown.