**4. Conclusions**

Polyimide films are used for spatial applications as they offer excellent thermal properties. As they are submitted to various charged particles and radiation during their lifetime, the determination of the ageing effect on such material is really challenging. In laboratories, many irradiation chambers have been developed so as to reproduce and couple the ageing sources such as electron radiation, proton radiation, UV exposure, atomic oxygen surface erosion, and temperature variation. In this chapter, the classic experimental measurements used to study materials for space applications have been presented. It is obvious that the surface potential decay is quite convenient to study the PI conductivity variation under various external conditions. It is also important to be able to characterize the SEE or photoconduction or surface flashover processes in order to mitigate ESD. In addition, the chemical analysis and the use of other techniques such as the PEA method to follow the dynamic of charge buildup and release are important to get a better understanding of the dielectric properties of PI under such an aggressive environment that remains quite difficult to reproduce entirely in laboratories. As mentioned, PI is very sensitive to air exposure, humidity, or UV exposure, so all the experiments must be performed with care in order to provide reliable data for the model that tend to reproduce satellite in its whole structure taking into account the material arrangement so as the surrounding environment.
