Aspace telescope (also known asspace observatory) is atelescope in outer space used to observe astronomical objects. Suggested byLyman Spitzer in 1946, the first operational telescopes were the AmericanOrbiting Astronomical Observatory,OAO-2 launched in 1968, and the SovietOrion 1 ultraviolet telescope aboard space stationSalyut 1 in 1971. Space telescopes avoid several problems caused by the atmosphere, including the absorption or scattering of certain wavelengths of light, obstruction by clouds, and distortions due to atmospheric refraction such astwinkling. Space telescopes can also observe dim objects during the daytime, and they avoidlight pollution whichground-based observatories encounter. They are divided into two types: Satellites which map the entire sky (astronomical survey), and satellites which focus on selectedastronomical objects or parts of the sky and beyond. Space telescopes are distinct fromEarth imaging satellites, which point toward Earth forsatellite imaging, applied forweather analysis,espionage, andother types of information gathering.

In 1946, American theoretical astrophysicistLyman Spitzer, "father of Hubble" proposed to put a telescope in space.^[1][2] 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 theHubble Space Telescope, which was launched on April 24, 1990, by theSpace ShuttleDiscovery (STS-31).^[3] This was launched due to many efforts by Nancy Grace Roman, "mother of Hubble", who was the first Chief of Astronomy and first female executive at NASA.^[4] She was a program scientist that worked to convince NASA, Congress, and others that Hubble was "very well worth doing".^[5]

The first operational space telescopes were the AmericanOrbiting Astronomical Observatory,OAO-2 launched in 1968, and the SovietOrion 1 ultraviolet telescope aboard space stationSalyut 1 in 1971.

Performingastronomy fromground-based observatories on Earth is limited by the filtering and distortion ofelectromagnetic radiation (scintillation or twinkling) due to theatmosphere. A telescope orbiting Earth outside the atmosphere is subject neither to twinkling nor tolight pollution from artificial light sources on Earth. As a result, theangular resolution of space telescopes is often much higher than a ground-based telescope with a similaraperture. Many larger terrestrial telescopes, however, reduce atmospheric effects withadaptive optics.^[6]

Space-based astronomy is more important for frequency ranges that are outside theoptical window and theradio window, the only two wavelength ranges of theelectromagnetic spectrum that are not severely attenuated by the atmosphere.^[6] 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 theChandra X-ray Observatory and theXMM-Newton observatory.Infrared andultraviolet are also largely blocked.

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 theSpace Shuttle, but most space telescopes cannot be serviced at all.

Satellites have been launched and operated byNASA,ISRO,ESA,CNSA,JAXA and theSoviet space program (later succeeded byRoscosmos 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 theCNSA, 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.^[7]

On 16 January 2023, NASA announced preliminary considerations of several future space telescope programs, including the Great Observatory Technology Maturation Program,Habitable Worlds Observatory, and New Great Observatories.^[8][9]

• Airborne observatory
• Balloon-borne telescope
• Earth observation satellite
• List of telescope types
• Timeline of artificial satellites and space probes
• Timeline of telescopes, observatories, and observing technology
• Ultraviolet astronomy
• X-ray telescope

• Lyman Spitzer,"Astronomical Advantages of an Extra-terrestrial Observatory", 1946
• Neil English:Space Telescopes – Capturing the Rays of the Electromagnetic Spectrum. Springer, Cham 2017,ISBN 978-3-319-27812-4.

•   Media related toSpace telescopes at Wikimedia Commons·
• Space telescopes with frequencies, at GSFC.