Thermal control of an innovative small GEO telecom platform (CX2)

CX2 is an innovative S/C platform for small telecommunication payloads in a Geostationary Orbit (GEO). It is an opportunity launcher passenger using excess launch capacity on the Ariane 5 launcher. The cylindrical shaped satellite is configured such that it respects the volume and mass constraints of the launcher and acts as a launcher load carrying structure. CX2 commences transfer to GEO using a Hall Effect high efficiency/low thrust Electric Propulsion System (EPS). The thermal control concept of CX2 is based on the use of north and south oriented external radiators for the telecommunication payload and high dissipating avionics. These radiators are equipped with embedded heat pipes and are split up in an isolated hot and cold section which operates at different temperatures to maximize efficiency. Heat pipes collect the dissipated heat of the equipment inside the S/C and transport it through the load carrying cylindrical structure to the cold section. The payload amplifiers are mounted directly on the hot sections of the external radiators. During the 200-days transfer phase, the payload is not operated and heater power is imposed directly on the transponders. Additional small radiator areas that are connected by heat pipes facilitate heat rejection for the other avionics. These radiator areas are part of the cylindrical primary structure and are located at the east and west sides. Dedicated heaters are installed to support thermal control of the external equipment, batteries, and the propellant storage and feed system. The two EPS thrusters require a dedicated thermal control during the transfer phase when both thrusters are operating side-by-side at maximum thrust.