Evaluation of nanoalumina coated germanium black polyimide membrane as sunshield for application on the communication satellite antenna

Alumina thin coatings were grown on Germanium (Ge) coated black polyimide (GBP) or Kapton which has been used as a sunshield membrane on communication satellite antennas to protect it from environmental degradation during ground storage and implementation. The deposited nanoalumina coatings were found to be optically transparent in solar regime in spectral window while RF characteristic revealed negligible losses. Space worthiness of the coating was examined by simulated environments, e.g. humidity, thermal cycling and thermovacuum tests. No degradation was observed in its microstructural, thermo-optical, electrical, chemical state and RF characteristic in particular Ku and Ka bands. The aforesaid study indicates that the alumina thin coating is able to prevent surface degradation of GBP retaining the thermo-optical properties of the Ge coated Kapton and RF transparency which are functional requirements for communication antenna. The thickness of the optimized alumina coating was ~60 nm.