Hubble Space Telescope metallized Teflon (R) FEP thermal control materials: on-orbit degradation and post-retrieval analysis

During the Hubble Space Telescope (HST) second servicing mission (SM2), deg radation of unsupported Teflon(R) FEP (fluorinated ethylene propylene), use d as the outer layer of the multilayer insulation (MLI) blankets, was evide nt as large cracks on the telescope light shield. A sample of the degraded outer layer was retrieved during the mission and returned to Earth for grou nd testing and evaluation. The results of the Teflon(R) FEP sample evaluati on and additional testing of pristine Teflon(R) FEP led the investigative t eam to theorize that the HST damage was caused by thermal cycling with deep -layer damage from electron and proton radiation which allowed the propagat ion of cracks along stress concentrations, and that the damage increased wi th the combined total dose of electrons, protons, ultraviolet and x-ray rad iation along with thermal cycling. This paper discusses the testing and eva luation of the retrieved Teflon(R) FEP.