To date, telecommunication and internet network are dominated by big-sized GEO satellites: several tons in mass and several kW in power demand. They are equipped with heavy and complex thermal control systems. Thermal control systems (TCS) are in charge of temperature control inside the satellite, ensuring that all components and devices stay in their operational (or survival when not working) temperature range. Due to the massive quantity of heat dissipation, active thermal control systems (ATCS) are used; their thermal handling capabilities are superior to those of passive thermal control systems (PTCS). Two-phase mechanically pumped fluid loops (2ΦMPFL) are among the most efficient ACTS.