The Polar Platform is a multi-mission platform designed to operate from low earth polar orbits. Its purpose is to accommodate and support various instrument complements dedicated to meteorology, earth observation and science.In its first mission configuration, ENVISAT-1, dedicated to earth observation, the lower three sections of the Payload Module represent the Payload Equipment Bay (PEB), which houses the payload support subsystem units and various payload instrument electronics equipment. All units are mounted on to the internal faces of the PEB CFRP honeycomb side panels.The PEB thermal design is basically passive, assisted by heaters and in general uses conventional techniques. However, thermal doublers, used to spread high heat fluxes over a greater area are made for the first time from carbon/carbon. This material matches the low coefficient of thermal expansion of the CFRP panels and at the same time provides the high thermal conductivity required for this application.This paper describes the thermal control of the PEB in general and focuses on the development of the, for this application, novel carbon/carbon material.