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)

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 communications satellite antennas to protect it from environmental degradation during ground storage and implementation. The deposited alumina 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 space 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

Optical and RF transparent protective alumina thin films

Protective alumina thin films of different thicknesses (35-95 nm) were grown by pulsed RF magnetron sputtering technique at room temperature on germanium (Ge) coated black polyimide (GBP) or Kapton® substrate which is often employed as sunshield membrane on communications satellite antennas. The thin alumina top layer provides shielding of Ge coating from degradation during storage. The alumina thin film was characterized by X-ray diffraction, field emission scanning electron microscopy and X-ray photoelectron spectroscopy techniques to investigate microstructural and electronic characteristics. Thermo-optical properties such as IR emittance, solar absorptance, reflectance and transmittance and electrical property e.g. sheet resistance of the deposited alumina films were measured. The RF losses e.g. insertion loss and return loss were measured in both Ku band (10.5 GHz to 14.5 GHz) and Ka band (27 GHz to 40 GHz). Finally, to prove anti-degradation behavior of alumina thin film, water droplet spreading experiments were carried out and evaluated it’s chemical degradation by XPS

Een planner voor een autonoom agent

SIGLEKULeuven Campusbibliotheek Exacte Wetenschappen / UCL - Université Catholique de LouvainBEBelgiu