The Hubble Space Telescope is a space telescope that was launched into low Earth
orbit in 1990 and remains in operation. With a 7.9 feet mirror, Hubble's four main
instruments observe in the near ultraviolet, visible, and near infrared spectra.
The telescope is named after the astronomer Edwin Hubble.
Hubble's orbit outside the distortion of Earth's atmosphere allows it to take
extremely high-resolution images with almost no background light. Hubble's Deep
Field has recorded some of the most detailed visible-light images ever, allowing a
deep view into space and time. Many Hubble observations have led to breakthroughs
in astrophysics, such as accurately determining the rate of expansion of the
universe.
Although not the first space telescope, Hubble is one of the largest and most
versatile, and is well known as both a vital research tool and a public relations
boon for astronomy. The HST was built by the United States space agency NASA, with
contributions from the European Space Agency, and is operated by the Space
Telescope Science Institute. The HST is one of NASA's Great Observatories, along
with the Compton Gamma Ray Observatory, the Chandra X-ray Observatory, and the
Spitzer Space Telescope.
Space telescopes were proposed as early as 1923. Hubble was funded in the 1970s,
with a proposed launch in 1983, but the project was beset by technical delays,
budget problems, and the Challenger disaster. When finally launched in 1990,
Hubble's main mirror was found to have been ground incorrectly, compromising the
telescope's capabilities. The optics were corrected to their intended quality by a
servicing mission in 1993.
Hubble is the only telescope designed to be serviced in space by astronauts. After
launch by Space Shuttle Discovery in 1990, four subsequent Space Shuttle missions
repaired, upgraded, and replaced systems on the telescope. A fifth mission was
canceled on safety grounds following the Columbia disaster. However, after
spirited public discussion, NASA administrator Mike Griffin approved one final
servicing mission, completed in 2009. The telescope is still operating as of 2014,
and may last until 2020. Its scientific successor, the James Webb Space Telescope,
is scheduled for launch in 2018.
