Astronauts aboard Space Shuttle Discovery released the Hubble Space Telescope into orbit roughly 340 miles above Earth on April 25, 1990. Despite an early flaw in its main mirror that blurred its first images, later corrected by a dramatic 1993 spacewalk repair, Hubble went on to capture some of the most iconic images in the history of astronomy.
The telescope's deployment came after years of delay, including the Challenger disaster, which pushed its launch back from an original 1986 target. Once in orbit, Hubble was supposed to deliver crystal-clear images unburdened by Earth's atmosphere, but engineers soon discovered its primary mirror had been ground to the wrong shape by a hair's breadth, producing fuzzy pictures that embarrassed NASA.
A 1993 servicing mission installed corrective optics, effectively giving the telescope glasses, and the fix worked spectacularly. Hubble went on to capture the Pillars of Creation, deep-field images showing thousands of galaxies in a single speck of sky, and evidence that helped confirm the accelerating expansion of the universe.
Decades after its rocky start, Hubble remains one of the most productive scientific instruments ever built, its images so embedded in public imagination that many people can picture its shots of nebulae and galaxies without knowing the telescope's name.
Key people: Edwin Hubble