Thermal design features of the ESA European Polar Platform are described. Due to the low conductivity of the CFRP/aluminium honeycomb sandwich panels of the Payload Equipment Bay, carbon/carbon thermal doublers are used as heat spreaders for high dissipating units. The main challenge for the thermal design of the Data Relay Satellite Terminal Outboard Assembly are the motor gears and the rotary joints. High RF dissipation combined with low thermal capacitances result in extreme orbital temperature variations. The temperature limits are met by a proper selection of thermooptical properties and thermostatically controlled heaters.