Abstract
We developed a potential monitor to measure the surface charging potentials on insulating materials for spacecraft due to charged particles in space environment. The potential monitor was installed on geostationary Engineering Test Satellite V of Japan which was launched on August 27, 1987. Three kinds of thermal control materials were used as samples. We obtained the following observational results: (1) The level of the charging potential depended on the environmental plasma condition and the material. (2) The rapid increase of the charging potential to be due to the shadows of the paddle and/or the antenna was occasionally observed. (3) For long time, the potential gradually increased under the shaded condition, but decreased in the sunlit condition.
