A method for monitoring the degradation of the optical density in films of polytetrafluoroethylene and its modification, a copolymer of tetrafluoroethylene and ethylene, irradiated by electrons with energies of 100 keV and 10 MeV is described. The method is based on measuring the optical density of irradiated films in the photon energy range of 1–6 eV and is confirmed by established “dose–optical absorption” relationships. In particular, using the described method, a completely different nature of the radiation degradation of the optical properties of the two types of films under study was discovered. With an increase in the irradiation dose, “clearing effect” in the region of 2–5 eV and the occurrence of an absorption band at 5.6 eV are observed in polytetrafluoroethylene films. With a similar dose increase, three absorption bands at 4.0, 4.6, and 5.5 eV appear and grow in films of copolymer of tetrafluoroethylene and ethylene. The evidence of the critical role of the optical density of films in the functioning of space technology devices is given.