Explore The Universe

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Featured Artifacts

Hubble Space Telescope Backup Mirror

main mirrors built by 
                    Corning for the Hubble Space Telescope
This is one of two nearly identical main mirrors built by Corning for the Hubble Space Telescope. The mirror installed on the Hubble was finished by Perkin-Elmer Corporation using computerized techniques. This backup mirror was finished by Eastman Kodak, which used conventional optical techniques to shape and polish the mirror.

Backup mirror transferred from NASA, courtesy of Kodak
Test cradle transferred from NASA, courtesy of Raytheon


  • How big is it? This mirror measures 2.5 meters (98 inches) across and weighs 748 kilograms (1,650 pounds). The useable surface of the mirror in the Hubble was slightly smaller-about 2.4 meters (94 inches)-because the mirror mounting covered the outer edge.
  • Why doesn't it look like a mirror? This mirror was never used, so it never received a reflective coating. The mirror in the Hubble was coated with a thin layer of aluminum and also overcoated with magnesium fluoride, so it could better reflect ultraviolet light.
  • What is it made of? The mirror is made of Corning ultra-low expansion glass. The front and back surfaces are fused to a lattice core and to the inner and outer bands, creating a sturdy but lightweight structure.

Behind The Scenes: Bringing The Backup Mirror to the National Air and Space Museum

Other Featured Artifacts in this section of the exhibit:
Hubble Space Telescope Wide-Field/Planetary Camera & CCD
Penzias and Wilson Pigeon Trap
High Resolution Imager (HRI)

Also In the Museum:
Hubble Space Telescope (Test Vehicle)
, on display in the "Space Race" exhibition.

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