A 1.3-millimeter spacing error in a test instrument left the Hubble Space Telescope's main mirror the wrong shape. Astronauts fixed its vision in December 1993.
ILLUSTRATION · AIHubble's main mirror was made the wrong shape because a lens in its test device was 1.3 millimeters out of place. Astronauts corrected its vision in December 1993.
Shortly after Hubble launched on April 24, 1990, engineers found its primary mirror had the wrong curve: too flat near its outer edge, an error 10 times larger than the tolerance its design needed.
Tracing the mistake
Investigators examined the null corrector, the device used to test the mirror nine years earlier, still in the same configuration. A lens spacing in it was off by 1.3 millimeters.
Glasses for a telescope
During the first servicing mission in December 1993, astronauts installed the Wide Field and Planetary Camera 2 and COSTAR, a corrective package about the size of a large refrigerator that acted like a pair of eyeglasses.
- Tier 2 · Secondary
More facts
NASA's space shuttles flew 135 missions in 30 years, from the first launch on April 12, 1981, to the final landing on July 21, 2011.
NASA's Vehicle Assembly Building is 525 feet tall. Its high bay doors are 456 feet high and take about 45 minutes to open or close completely.
