The LHED value is the critical “fluence” value where the structure of an optical component exposed to a high power/energy and focused laser beam (continuous/pulsed) changes irreversibly. “Fluence” value is expressed as power/energy per unit area (W/cm2 or J/cm2). Determining the LHED values of optical components of these systems, including high-power laser systems, is a very important test application as it can affect the durability of the entire system. Today, the ISO 21254:1-3 family of standards is in force to carry out these tests in an atmospheric environment. These standards regulate the LHED tests of all coated and uncoated optical components produced for scientific, industrial and commercial purposes, especially for the defense industry, in the atmospheric environment. In recent years, the number of research on space research has been increasing rapidly in our country and around the world. Within the scope of these researches, it has become important to determine the properties of coated and uncoated optical components in the optical assemblies and to turn them into internationally valid standard specifications. For this purpose, LaTSO Project is carried out at TÜBİTAK UME Thermodynamic Metrology Laboratory.