The Hubble Space Telescope is a space telescope that was launched into low Earth orbit in 1990 and remains in operation.
A space telescope or space observatory is an instrument located in outer space to observe distant planets, galaxies and other astronomical objects.
A low Earth orbit is an orbit around Earth with an altitude between 160 kilometers, and 2,000 kilometers.
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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.
Astronomy is a natural science that studies celestial objects and phenomena.
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The HST is named after the astronomer Edwin Hubble, 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.
The National Aeronautics and Space Administration is an independent agency of the executive branch of the United States federal government responsible for the civilian space program as well as aeronautics and aerospace research.
The Chandra X-ray Observatory, previously known as the Advanced X-ray Astrophysics Facility, is a Flagship-class space observatory launched on STS-93 by NASA on July 23, 1999.
An astronomer is a scientist in the field of astronomy who concentrates their studies on a specific question or field outside of the scope of Earth.
With a 2.4-meter mirror, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared spectra.
A mirror is an object that reflects light in such a way that, for incident light in some range of wavelengths, the reflected light preserves many or most of the detailed physical characteristics of the original light.
Infrared radiation, or simply infrared or IR, is electromagnetic radiation with longer wavelengths than those of visible light, and is therefore invisible, although it is sometimes loosely called infrared light.
Ultraviolet is an electromagnetic radiation with a wavelength from 10 nm to 400 nm, shorter than that of visible light but longer than X-rays.
Hubble's orbit outside the distortion of Earth's atmosphere allows it to take extremely high-resolution images, with substantially lower background light than ground-based telescopes.
The atmosphere of Earth is the layer of gases, commonly known as air, that surrounds the planet Earth and is retained by Earth's gravity.
An atmosphere is a layer of gases surrounding a planet or other material body, that is held in place by the gravity of that body.
Hubble has recorded some of the most detailed visible light images ever, allowing a deep view into space and time.
Light is electromagnetic radiation within a certain portion of the electromagnetic spectrum.
Many Hubble observations have led to breakthroughs in astrophysics, such as accurately determining the rate of expansion of the universe.
Astrophysics is the branch of astronomy that employs the principles of physics and chemistry "to ascertain the nature of the heavenly bodies, rather than their positions or motions in space."
The HST was built by the United States space agency NASA, with contributions from the European Space Agency.
The European Space Agency is an intergovernmental organisation of 22 member states, dedicated to the exploration of space.
The Space Telescope Science Institute selects Hubble's targets and processes the resulting data, while the Goddard Space Flight Center controls the spacecraft.
The Goddard Space Flight Center is a major NASA space research laboratory established on May 1, 1959 as NASA's first space flight center.
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.
An astronaut or cosmonaut is a person trained by a human spaceflight program to command, pilot, or serve as a crew member of a spacecraft.
After launch by Space Shuttle Discovery in 1990, five subsequent Space Shuttle missions repaired, upgraded, and replaced systems on the telescope, including all five of the main instruments.
The Space Shuttle was a partially reusable low Earth orbital spacecraft system operated by the U.S. National Aeronautics and Space Administration, as part of the Space Shuttle program.
The fifth mission was canceled on safety grounds following the Columbia disaster.
However, after spirited public discussion, NASA administrator Mike Griffin approved the fifth servicing mission, completed in 2009.
The telescope is operating as of 2017, and could last until 2030–2040.
Its scientific successor, the James Webb Space Telescope, is scheduled for launch in 2018.