Fundamental Research on Surface Discharge Phenomena of Insulation Materials in space Environment

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Spacecraft charging is considered a major cause of malfunctions of spacecrafts on high altitude, such as geosynchronous satellites. An experimental study on the discharge phenomena on polymer films irradiated by an electron beam in a high-vacuum chamber, which simulates the spacecraft charging and discharging, has been performed.1. Major differences between the space environment and the high-vacuum chamber in a laboratory, which affect the spacecraft charging and discharging phenomena, are supposedly the temperature and the pressure of the residual gas. The temperature influences the conductivity of insulation materials. It dominates the charging phenomena, however, it is believed to be less influential on the discharge phenomena.2. The gas pressure realized in a laboratory is still considerably higher than the space environment at the altitude of the geosynchronous orbit. As a result of this research, the residual gas has been known to play an important role in the initiation of surfa … More ce discharges. As the conditioning effect is observed in both the condition of the initiation of surface discharge and the spectrum of discharge light, the arc discharge will be harder to occur in the space environment where residual gas molecules are much less. Smoothing the interface between the insulation materials and metallic surface will also help the discharge potential to rise.3. In spite of the above findings, discharges on spacecrafts on the geosynchronous orbit have been actually observed. This fact suggests that release of gas molecules absorbed in the insulation materials on the surface of spacecrafts may be an important factor in the discharge phenomena. Therefore, the simulation of the phenomena in a vacuum chamber is known to be useful in investigating the spacecraft charging and discharging.4. The molecules of residual gas also affect deterioration of some kind of insulation material associated with surface discharges, which is known by the mass-spectrum analysis of released gas. This fact has to be taken into account in the evaluation of spacecraft materials in a space chamber. Less