Hubble "Witness Sample"
Even with this protection is was standard practice to include small samples with the main mirror. The small samples could be tested from time to time to keep track of the coating on the main mirror. This sample was flown into space on the deployment mission as a commemorative gesture and was presented to the popular magazine Sky & Telescope. Rick Feinberg, former editor of S&T, donated it for the exhibit.
Image Number: WEB13921-2014
Credit: Image by Eric Long, National Air and Space Museum, Smithsonian Institution
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