A space telescope or space observatory is a

telescope A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to observ ...

in outer space used to observe astronomical objects. Suggested by

Lyman Spitzer Lyman Spitzer Jr. (June 26, 1914 – March 31, 1997) was an American theoretical physicist, astronomer and mountaineer. As a scientist, he carried out research into star formation, plasma physics, and in 1946, conceived the idea of telesco ...

in 1946, the first operational telescopes were the American

Orbiting Astronomical Observatory The Orbiting Astronomical Observatory (OAO) satellites were a series of four American space observatories launched by NASA between 1966 and 1972, managed by NASA Chief of Astronomy Nancy Grace Roman. These observatories, including the first su ...

, OAO-2 launched in 1968, and the Soviet Orion 1 ultraviolet telescope aboard space station

Salyut 1 Salyut 1 (DOS-1) (russian: Салют-1) was the world's first space station launched into low Earth orbit by the Soviet Union on April 19, 1971. The Salyut program followed this with five more successful launches of seven more stations. The f ...

in 1971. Space telescopes avoid the filtering and distortion ( scintillation) of

electromagnetic radiation In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic (EM) field, which propagate through space and carry momentum and electromagnetic radiant energy. It includes radio waves, microwaves, infrared, (visible) li ...

which they observe, and avoid

light pollution Light pollution is the presence of unwanted, inappropriate, or excessive use of artificial Visible spectrum, lighting. In a descriptive sense, the term ''light pollution'' refers to the effects of any poorly implemented lighting, during the day ...

which ground-based observatories encounter. They are divided into two types: Satellites which map the entire sky (

astronomical survey An astronomical survey is a general map or image of a region of the sky (or of the whole sky) that lacks a specific observational target. Alternatively, an astronomical survey may comprise a set of images, spectra, or other observations of ob ...

), and satellites which focus on selected

astronomical objects An astronomical object, celestial object, stellar object or heavenly body is a naturally occurring physical entity, association, or structure that exists in the observable universe. In astronomy, the terms ''object'' and ''body'' are often us ...

or parts of the sky and beyond. Space telescopes are distinct from Earth imaging satellites, which point toward Earth for

satellite imaging Satellite images (also Earth observation imagery, spaceborne photography, or simply satellite photo) are images of Earth collected by imaging satellites operated by governments and businesses around the world. Satellite imaging companies sell ima ...

, applied for weather analysis,

espionage Espionage, spying, or intelligence gathering is the act of obtaining secret or confidential information (intelligence) from non-disclosed sources or divulging of the same without the permission of the holder of the information for a tangib ...

, and other types of information gathering.

History

Wilhelm Beer Wilhelm Wolff Beer (4 January 1797 – 27 March 1850) was a banker and astronomer from Berlin, Prussia, and the brother of Giacomo Meyerbeer. Astronomy Beer's fame derives from his hobby, astronomy. He built a private observatory with a ...

and Johann Heinrich Mädler in 1837 discussed the advantages of an observatory on the Moon. In 1946, American theoretical astrophysicist

proposed a telescope in space. Spitzer's proposal called for a large telescope that would not be hindered by Earth's atmosphere. After lobbying in the 1960s and 70s for such a system to be built, Spitzer's vision ultimately materialized into the

Hubble Space Telescope The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most vers ...

, which was launched on April 24, 1990 by the Space Shuttle ''Discovery'' (STS-31). The first operational space telescopes were the American

, OAO-2 launched in 1968, and the Soviet Orion 1 ultraviolet telescope aboard space station

in 1971.

Advantages

Performing

astronomy Astronomy () is a natural science that studies celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and evolution. Objects of interest include planets, moons, stars, nebulae, g ...

from ground-based observatories on Earth is limited by the filtering and distortion of

( scintillation or twinkling) due to the atmosphere. A telescope orbiting Earth outside the atmosphere is subject neither to twinkling nor to

from artificial light sources on Earth. As a result, the angular resolution of space telescopes is often much higher than a ground-based telescope with a similar

aperture In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane. An ...

. Many larger terrestrial telescopes, however, reduce atmospheric effects with

adaptive optics Adaptive optics (AO) is a technology used to improve the performance of optical systems by reducing the effect of incoming wavefront distortions by deforming a mirror in order to compensate for the distortion. It is used in astronomical tele ...

Space-based astronomy is more important for frequency ranges that are outside the

optical window The optical window is a range of wavelengths that are not blocked by the earth's atmosphere. The window runs from around 300 nanometers (ultraviolet-B) up into the range the human eye can detect, roughly 400–700 nm and continues up to approxim ...

and the radio window, the only two wavelength ranges of the

electromagnetic spectrum The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies. The electromagnetic spectrum covers electromagnetic waves with frequencies ranging fro ...

that are not severely attenuated by the atmosphere. For example, X-ray astronomy is nearly impossible when done from Earth, and has reached its current importance in astronomy only due to orbiting X-ray telescopes such as the

Chandra X-ray Observatory The Chandra X-ray Observatory (CXO), previously known as the Advanced X-ray Astrophysics Facility (AXAF), is a Flagship-class space telescope launched aboard the during STS-93 by NASA on July 23, 1999. Chandra is sensitive to X-ray sources 1 ...

and the XMM-Newton observatory.

Infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

and

ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation ...

are also largely blocked.

Disadvantages

Space telescopes are much more expensive to build than ground-based telescopes. Due to their location, space telescopes are also extremely difficult to maintain. The Hubble Space Telescope was serviced by the

Space Shuttle The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program ...

, but most space telescopes cannot be serviced at all.

Future of space observatories

Satellites have been launched and operated by

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the US federal government responsible for the civil List of government space agencies, space program ...

, ISRO,

ESA , owners = , headquarters = Paris, Île-de-France, France , coordinates = , spaceport = Guiana Space Centre , seal = File:ESA emblem seal.png , seal_size = 130px , image = Views in the Main Control Room (120 ...

CNSA China National Space Administration (CNSA; ) is the government agency of the People's Republic of China that is responsible for civil space administration and international space cooperation, including organizing or leading foreign exchanges ...

, JAXA and the

Soviet space program The Soviet space program (russian: Космическая программа СССР, Kosmicheskaya programma SSSR) was the national space program of the former Union of Soviet Socialist Republics (USSR), active from 1955 until the dissoluti ...

(later succeeded by

Roscosmos The State Space Corporation "Roscosmos" (russian: Государственная корпорация по космической деятельности «Роскосмос»), commonly known simply as Roscosmos (russian: Роскосмос) ...

of Russia). As of 2022, many space observatories have already completed their missions, while others continue operating on extended time. However, the future availability of space telescopes and observatories depends on timely and sufficient funding. While future space observatories are planned by NASA, JAXA and the

, scientists fear that there would be gaps in coverage that would not be covered immediately by future projects and this would affect research in fundamental science. For example, there was a fear that there would be a gap in coverage between the

and the James Webb Space Telescope (JWST).

List of space telescopes

References

External links

* · {{DEFAULTSORT:Space Observatory American inventions Astronomical observatories Telescope types Uncrewed spacecraft