April 24, 1990 — NASA looked snakebit in the early days of the Hubble mission. Not long after the extraordinary space telescope was launched, horrified designers realized they had miscalibrated the manufacturing of its main mirror, turning what should have been the sharpest images in the history of astronomy into useless blobs of light. It would be impossible to replace the mirror in orbit, but it would be possible to install hardware to sharpen the pictures — essentially corrective lenses. A later space-shuttle mission was launched to do that work, and three other shuttles performed routine servicing missions into 2002. The Hubble has responded by pouring back a tidal wave of imagery and data, exponentially expanding what astronomers know about the universe. It is probably the finest space machine ever built — and the shuttle, for once, did its part.