**3. Complementary tools**

As discussed in the previous section, there is a large number of conventional tests that have been selected and validated to study material used in a space environment. New tools have been developed to provide complementary information. For instance, the pulse electro acoustic (PEA) method that was commonly used since the 1980s to study the material encountered in electrical engineering application has been adapted to characterize the material under vacuum. This method has been developed to be also efficient to study materials under various conditions such as electron or proton irradiation and under various temperatures in the last 18 years.
