Thermal analysis is the name of a collection of techniques that investigates material properties as a function of temperature. Four main techniques which all look at specific material properties are differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), thermomechnical analysis (TMA) and dynamic mechanical analysis (DMA). The commercially available polyimide foils Kapton HN and Upilex S are often used as external thermal control material on spacecraft. For missions to the inner part of the solar system, these materials need to withstand an elevated service temperature in combination with high intensity solar radiation, such as UV and protons. The thermal stability of Kapton and Upilex has been investigated at around 250 1 C for a mission to Venus and at 350 1 C for a mission to Mercury. Samples were aged at representative temperature levels, also in combination with high intensity UV and proton radiation. It was found that TMA and DMA revealed, in good detail, the environmental effects of the behavior of the materials. Both foils are known to be thermally stable materials. Assessment by TGA and kinetic modeling indicates a better stability of Upilex at 350 1 C. The DMA experiments of foils aged at 350 1 C for up to 3580 h prove that the glass transition of Kapton is largely affected and almost completely disappears. Upilex is also affected but remains more stable. The TMA assessment revealed annealing of residual stresses at elevated temperature that cause (partial) shrinking of the foils. Ageing at around 250 1 C causes such annealing besides other more subtle changes. The added irradiation to high intensity UV and protons does not cause significant changes compared to thermal ageing alone. The DMA results are in good agreement with the TMA. The behavior of Upilex is deemed to be somewhat less affected by the environmental testing than Kapton.

Teflon R 1 fluorinated ethylene propylene (FEP) is used on the Hubble Space Telescope (HST) as the outer layer of multilayer insulation (MLI) blankets. During space shuttle servicing missions (SM) to HST through thickness cracks were observed in the FEP layers. Material brought to Earth for investigation showed signs of severe degradation. During servicing mission 3B, the 4th servicing mission to HST in March 2002, the second pair of European Space Agency ESA built solar arrays was retrieved and flown back to Earth after 8.25 years in space. Samples of the MLI thermal control material were taken from the solar array drive arm (SADA) and investigated for surface and bulk degradation. The MLI was enveloped around the SADA and thus allowed the examination of FEP degradation in dependence of the orientation of space exposed areas with respect to the Sun. Therefore micrographs of FEP surfaces and fractographs of through thickness cracks were taken and the solar absorptance 1 S and the normal emittance 2 N was measured on the entire MLI. Differential scanning calorimetrical analyses as well as electron spectroscopy for chemical analyses were conducted to analyze chemical changes of the bulk polymer and the surface layer, respectively. Tensile properties and mass losses of the space exposed material were evaluated as well. Results of the investigated thermal control material are compared with samples exposed on the ground to thermal cycling, soft X-rays and vacuum ultra-violet radiation as well as to previously reported results on space-exposed FEP. The paper thus gives further insight into the mechanism and processes contributing to the on orbit degradation of Teflon R 1 FEP and correlates the presented data with exposure levels and exposure conditions. Downloaded from 430 M. MOSER ET AL. Figure 1. Right: Hubble Space Telescope with axis system. The position of the investigated multilayer insulation (MLI) on the solar array drive arm (SADA) is indicated1 Left: SADA MLI with grid system.