Space Travel and Exploration
Hubble Space Telescope

What is the Hubble Space Telescope?

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2009-03-20 05:24:10

The Hubble Space Telescope (HST) is a space

telescope that was carried into orbit by the Space Shuttle

Discovery in April 1990. It is named for the American astronomer

Edwin Hubble. Although not the first space telescope, the 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 is a collaboration between NASA and the European Space Agency,

and 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. The 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, scientists found that the main mirror had been ground

incorrectly, severely compromising the telescope's capabilities.

However, after a servicing mission in 1993, the telescope was

restored to its intended quality. Hubble's position outside the

Earth's atmosphere allows it to take extremely sharp images with

almost no background light. Hubble's Ultra Deep Field image, for

instance, is the most detailed visible-light image of the

universe's most distant objects ever made. Many Hubble observations

have led to breakthroughs in astrophysics, such as accurately

determining the rate of expansion of the universe. The Hubble is

the only telescope ever designed to be serviced in space by

astronauts. To date, there have been four servicing missions.

Servicing Mission 1 took place in December 1993 when Hubble's

imaging flaw was corrected. Servicing missions 2, 3A, and 3B

repaired various sub-systems and replaced many of the observing

instruments with more modern and capable versions. However,

following the 2003 Columbia Space Shuttle disaster, the

fifth servicing mission was canceled on safety grounds. After

spirited public discussion, NASA reconsidered this decision, and

administrator Mike Griffin gave the green light for one final

Hubble servicing mission. This was planned for October 2008, but in

September 2008, another key component failed. The servicing mission

has been postponed until May 2009 to allow this unit to be replaced

as well. The planned repairs to the Hubble should allow the

telescope to function until at least 2013, when its successor, the

James Webb Space Telescope (JWST), is due to be launched. The JWST

will be far superior to Hubble for many astronomical research

programs, but will only observe in infrared, so it would complement

(not replace) Hubble's ability to observe in the visible and

ultraviolet parts of the spectrum.

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