Hubble Space Telescope Backup Mirror

This is the backup primary mirror for the Hubble Space Telescope manufactured by the Eastman Kodak Company. The blank for this mirror was fabricated by the Corning Glass Works using their high silicon Ultra Low Expansion Glass (ULE 7971). It consists of two 1-inch glass disks fused to the faces of a thin square eggcrate-like support structure. This support structure creates a mirror that weighs about one-fifth that of a solid piece of the same size but retains required rigidity and stability characteristics. The blank mirror was sent to the Kodak Apparatus Division located in Rochester, NY, when they won a NASA contract to create the back-up optical mirror. Kodak ground the mirror surface into the proper concave shape and then polished it to successively finer tolerances using computer-assisted testing routines. The finished mirror was tested and verified by Kodak to meet the strict optical tolerances prescribed by NASA. It was left un-aluminized mirror and delivered to the Perkin-Elmer Corporation in Danbury Connecticut, the prime contractor for the flight mirror, and was stored there until the end of 2000, at which time NASA determined that its value as a display object was greater than its potential value as a telescope mirror. It was then transferred from NASA to NASM by Raytheon, who absorbed Perkin-Elmer.