Solar array paddle for the Advanced Land Observing Satellite (ALOS): Charging mitigation and verification

A large solar array paddle with the power generation of 7 kW was developed for the Advanced Land Observing Satellite (ALOS). With the deployed dimension of 22 x 3 m in a polar orbit, this 9-panel rigid paddle has insulator Silver-Teflon thermal sheets and exposed bypath diode boards on its back face, and cover-glass integrated silicon solar cells on its front face. A charging analysis suggested that large negative potentials on the dielectric back-surfaces and at satellite ground may be induced through the ALOS's auroral passage in off-nominal conditions. The ALOS's baseline panel design was tested for the electron beam radiation and the plasma interaction, which simulated charging situations near the poles. Both the back face and the front face were tested, and arc thresholds were identified. Possibility of sustained arc and surge voltage, as well as survivability against estimated accumulation of arcs, were investigated. The back face showed small negative arc thresholds for both the insulator surface potential and the spacecraft ground voltage. Surface flashover was observed over the silver-Teflon coating. Although both the back and front faces demonstrated immunity against sustained arcs, design modifications to mitigate the back face's susceptibility for charging and arcing were experimentally examined and implemented. The conductive adhesive that surrounded the baseline Silver-Teflon sheet and covered the CFRP face-sheets eliminated arcs at the silver-Teflon edges and the face-sheet. The Kapton film shielding the diode board protected the exposed power line from arcs.
資料番号: AA0049206097
レポート番号: JAXA-SP-05-001E