Hubble Space Telescope (STS-31)

The Hubble Space Telescope rode to orbit aboard Space Shuttle Discovery on April 24, 1990, promising astronomy free of the atmosphere’s blur. Within weeks, engineers discovered its 2.4-meter mirror had been ground to the wrong shape by a fraction of the width of a human hair. The 1993 servicing mission that installed corrective optics — five spacewalks of watchmaker precision — became one of spaceflight’s greatest redemption stories.

Since then, Hubble has made more than 1.5 million observations: measuring the universe’s expansion rate, imaging the Hubble Deep Fields that revealed thousands of galaxies in a speck of dark sky, and producing images that made nebulae household art. Serviced five times by shuttle crews, it remains a working observatory after more than three decades.