“But this would have led to temperatures of 700 ☌ onthe Sun-facing side of the heat shield, and required a much bulkier shield structure with extra multilayer insulation. “We were left to consider the option of bare, uncoated titanium,” notes ESA thermal engineer Claudio Damasio. And in vibration testing they released too many particles. Existing paints or coatings either could not withstand the solar heat and radiation or were not conductive across the required temperature range. This combination of requirements proved too much. Finally there could be no outgassing or shedding of particles, which might endanger the mission’s instrument lenses, mirrors and sensitive surfaces.” “Secondly it had to be electrically conductive, to prevent any build-up of static from interaction with the solar wind, which might do damage to the spacecraft by discharging and disturb the payload’sprecise measurements of electrons in the solar wind. So we settled on black, to keep its thermo-optical properties stable over the mission lifetime. “Firstly it had to keep the same colour during years of exposure to intense solar flux, including high ultraviolet radiation – the mission team would have loved a white coating, to reflect back more solar energy, but testing showed it would darken unacceptably over time. “The mission had three main requirements for the heatshield covering,” explains ESA materials engineer Andrew Norman. The search for a sunscreen Solar Orbiter during thermal-vacuum tests
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