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A space telescope (also known as space observatory) is a telescope in outer space used to observe astronomical objects. Suggested by Lyman Spitzer in 1946, the first operational telescopes were the American Orbiting Astronomical Observatory, OAO-2 launched in 1968, and the Soviet Orion 1 ultraviolet telescope aboard space station Salyut 1 in 1971. Space telescopes avoid several problems caused by the Earth's atmosphere, including the absorption or scattering of certain wavelengths of light, obstruction by clouds, and distortions due to atmospheric refraction such as twinkling. Space telescopes can also observe dim objects during the daytime, and they avoid light pollution which ground-based observatories encounter. They are divided into two types: Satellites which map the entire sky (astronomical survey), and satellites which focus on selected astronomical objects or parts of the sky and beyond. Space telescopes are distinct from Earth imaging satellites, which point toward Earth for satellite imaging, applied for weather analysis, espionage, and other types of information gathering.
In 1946, American theoretical astrophysicist Lyman Spitzer, aka "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 1970s for such a system to be built, Spitzer's vision ultimately materialized into the Hubble Space Telescope, which was launched on April 24, 1990, by the Space Shuttle Discovery (STS-31).[3] This was launched due to many efforts by Nancy Grace Roman, aka "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, the U.S. Congress, and others that Hubble was "very well worth doing".[5]
最初に運用された宇宙望遠鏡は、1968年に打ち上げられたアメリカの軌道天文台OAO-2と、 1971年に宇宙ステーション「サリュート1号」に搭載されたソ連の紫外線望遠鏡オリオン1号である。
地球上の地上観測所から天文学を行うには、大気による電磁放射のフィルタリングと歪み（シンチレーションまたはトゥインクル）によって制限されます。大気圏外の地球を周回する望遠鏡は、トゥインクルも地球上の人工光源からの光害も受けません。その結果、宇宙望遠鏡の角度分解能は、同じ口径の地上望遠鏡よりもはるかに高い場合が多いです。ただし、多くの大型地上望遠鏡は、補償光学によって大気の影響を軽減しています。[ 6 ]
宇宙天文学は、大気によって著しく減衰されない電磁スペクトルの 2 つの波長範囲である光学窓と電波窓の外側の周波数範囲にとってより重要です。 [ 6 ]地球の大気はX 線を遮断し、[ 7 ]また赤外線[ 8 ]と紫外線[ 9 ]も大部分遮断するため、チャンドラ X 線観測衛星、ジェームズ ウェッブ宇宙望遠鏡、XMM-ニュートン観測衛星、および (現在は運用停止中の)国際紫外線探査機などの望遠鏡や観測所は地球の大気圏上空に設置されています。[ 10 ]
さらに、大気屈折をいわゆるテラスコープのレンズとして利用すること、あるいは太陽重力レンズを利用した望遠鏡の重力レンズとして利用することが提案されており、どちらのアプローチも並外れた望遠鏡解像度を実現する可能性を秘めている。[ 11 ]
宇宙望遠鏡は地上望遠鏡に比べて建造コストがはるかに高い。また、設置場所の特性上、維持管理も極めて困難である。ハッブル宇宙望遠鏡はスペースシャトルによって整備されたが、ほとんどの宇宙望遠鏡はそもそも整備が不可能である。
Satellites have been launched and operated by NASA, ISRO, ESA, CNSA, JAXA and the Soviet space program (later succeeded by Roscosmos 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 CNSA, 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.[12]
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.[13][14]
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