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The Hubble Space Telescope was designed to free astronomers of a limitation that has plagued them since the days of Galileo—Earth's atmosphere. Shifting air pockets in the atmosphere block and distort light, limiting the view from even the most powerful Earth-bound instruments.
Orbital telescopes function as eyes in the sky that allow astronomers to peer farther into the universe and see the cosmos more clearly.
Scientists began dreaming of such a telescope in the 1940s, but it took more than four decades for those dreams to become reality with the Hubble Space Telescope. The telescope's original October 1986 launch was scrapped after the loss of the space shuttle Challenger.
When the telescope finally became operational in 1990, it began to return unprecedented but flawed images. Its images were superior to those of Earth-bound instruments but slightly blurred due to an optical problem.
In December 1993 astronauts from the space shuttle Endeavour performed five days of spacewalks to repair the telescope in orbit some 353 miles (569 kilometers) above the Earth. The repair worked, and Hubble began to deliver crystal-clear images....
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