Abstract: The heat pipe is an important heat transfer element in thermal control design, which is used in a large number of GEO long-life satellites. On-orbit isothermal heat transfer performance of the heat pipe is a key factor affecting the safe and reliable operation of satellites. Aiming at studying the heat pipe of GEO longlife satellites that have long-term stable operation on orbit in China, the mathematical statistics method was used to analyze the law of the onorbit isothermal performance of the heat pipe with time, based on the temperature telemetry date on orbit. Results show that the heat pipe of GEO long-life satellites has good isothermal stability on orbit. The isothermal performance is greatly affected by the temperature level of the heat pipe. And it shows seasonal changes during the annual cycle and a downward trend in performance degradation over the entire life cycle with the flight time. The isothermal performance of the heat pipe at the end of its life is better than 1.6℃. In this paper, the isothermal improvement analysis and application suggestions are made from the aspects of heat pipe design, heat load size and distribution and its using environment.

Key words: long-life satellites, heat pipe, onorbit, isothermal performance