A study on degradation of germanium coating on Kapton used for spacecraft sunshield application

Sunshield membranes made of germanium coated black polyimide (GBP) or Kapton are often used on the reflector/transmitter antenna of satellites for thermal control applications. However, the germanium top layer is prone to degrade during ground storage and implementation. Hence vacuum/inert gas sealed packaging is required for storing the membranes, followed by a staggered fabrication schedule as the shelf-life of the GBP is identified as only ~ 6 months. In the present study, microstructural, thermo-optical and electrical properties along with XPS studies for evaluating oxidation states of the as-received and degraded GBP films have been investigated thoroughly. The radio frequency (RF) loss behaviour of both the films has also been studied for S band (2.5 GHz- 3.5 GHz), Ku band (10.5 GHz- 14.5 GHz) and Ka Band (30 GHz- 35 GHz).