As heat generation in satellites increases, ensuring that they are provided with sufficient radiator panel area is an important problem. Deployable radiators, with radiator panels that are deployed post-launch in space to increase the satellite's effective radiator panel area, are becoming an important thermal control technology. For the deployable radiator mounted in KIKU-8 satellite, we previously developed a reservoir embedded loop heat pipe (RELHP). RELHP is made to operate more reliably by incorporating a fluid-filled reservoir into the evaporator and forming axial grooves in the interior surface of the wick so that the wick remains wet under any microgravity condition. This paper presents temperature oscillations phenomena of the RELHP for use on the deployable radiator under a geostationary orbital environment by experiments and calculations. Firstly, a transient calculation model which can predict the deployable radiator's heat characteristics on the orbit was developed. Next, calculated results were compared with experimental results. It was found that the sub-cooling region is shorter, in a microgravity environment than in a terrestrial gravity environment, because there is less heat leakage into the reservoir in a microgravity environment. And that is cause of temperature oscillations.
