Tailor-made for XMM
24 January 1999Elizabeth Zehetbauer started working in the space sector six years ago. At the Austrian Aerospace facility at Berndorf in Lower Austria, she belongs to the department that produces the thermal insulation for spacecraft.
After leaving college, Elisabeth spent four years studying clothes-making and envisaged a job in tailoring or haute-couture. Until she saw an Austrian Aerospace advertisement, she never imagined that one day she would be dressing satellites!
XMM is not the first science spacecraft she and her colleagues have carefully wrapped. She has previously worked on ESA's SOHO and Cluster programmes. But it was with great pride that she talked about XMM, as she fastened this special material to the focal plane assembly of XMM during its final integration at Dornier.
MLI (Multilayer insulation) is made up of many layers (up to 20) of paper-thin, silver-coloured metalised polyester sandwiched with a thin veil material. Total thickness is less that half a centimeter. The outside black layer, carbon-loaded 'Kapton', is electrically conductive and resists radiation.
From the raw material, MLI is manufactured in long sheets in Berndorf and is pre-cut by hand using scissors and scalpels. Even if the templates provided are very precise, final fitting to the spacecraft needs manual adjustments. Each piece is clipped onto small plastic pedestals leaving a few centimeters between the insulation and the satellite's metallic structures. Generally the segments just overlap, a few are bonded together but - joked Elisabeth - "I no longer do any stitching or sewing!"
The insulation covering practically the entire outside surface of the satellite has three objectives: The first is thermal insulation, protecting XMM from the warmth of the Sun (150°C) and the bitter cold of deep space (-269°C). It also ensures electrical conductivity, preventing the accumulation of electrostatic charges at the surface of the spacecraft; produced by particles hitting the spacecraft, high electric potentials could entail risks of discharges damaging onboard equipment. Finally the MLI acts as a supplementary barrier where any micro-meteorites that pass through the insulation would be vaporized.
Austrian Aerospace has also provided the XMM sunshield, the doors in front of its mirror modules and the venting structure on the telescope tube. As Elisabeth punched a small hole in a piece of MLI, one of her Austrian Aerospace colleagues proudly remarked : "Yes, in this high-tech industry, there still are artisans!".