The Hubble Space Telescope was nearly blind for its first three years because its primary mirror was ground too flat by 2.2 micrometers, and NASA's reputation depended on a 1993 repair mission built around corrective optics the size of a refrigerator

The Hubble Space Telescope was nearly blind for its first three years because its primary mirror was ground too flat by 2.2 micrometers, and NASA's reputation depended on a 1993 repair mission built around corrective optics the size of a refrigerator

The Hubble Space Telescope went into orbit in April 1990 with a primary mirror polished to the wrong shape by 2.2 micrometers, a figure smaller than a fiftieth of a human hair and yet large enough to make a $1.5 billion observatory take pictures roughly as blurry as a good ground telescope on a clear night. The defect was called spherical aberration. It meant that light hitting the outer edge of the 2.4-meter mirror focused in a slightly differe…