Great Observatories program

<a href="/facts/NASA/TIMCV0yV">NASA</a>'s series of Great Observatories <a href="/facts/Satellite/PTX8c68t">satellites</a> are four large, powerful <a href="/facts/Space_telescope/BtI46sDX">space-based astronomical telescopes</a> launched between 1990 and 2003. They were built with different technology to examine specific wavelength/energy regions of the <a href="/facts/Electromagnetic_spectrum/24LARvFY">electromagnetic spectrum</a>: <a href="/facts/Gamma_ray/5Drf913J">gamma rays</a>, <a href="/facts/X-ray/wseP79cN">X-rays</a>, <a href="/facts/Visible_light/jeofpMn4">visible</a> and <a href="/facts/Ultraviolet_light/kncBUqn5">ultraviolet light</a>, and <a href="/facts/Infrared/44XdJNcc">infrared light</a>.
The <a href="/facts/Hubble_Space_Telescope/NQeIf0vw">Hubble Space Telescope</a> (HST) primarily observes <a href="/facts/Optical_spectrum/frPBh8o5">visible light</a> and <a href="/facts/Near_ultraviolet/kncBUqn5">near-ultraviolet</a>. It was launched in 1990 aboard the <a href="/facts/Space_Shuttle_Discovery/MmSTr4G0">Space Shuttle Discovery</a> during <a href="/facts/STS-31/daJMCUIY">STS-31</a>, but its main mirror had been ground incorrectly, resulting in <a href="/facts/Spherical_aberration/x7V1JMQ9">spherical aberration</a> that compromised the telescope's capabilities. The optics were corrected to their intended quality by the <a href="/facts/STS-61/AvAnmTdx">STS-61</a> servicing mission in 1993. In 1997, the <a href="/facts/STS-82/5TKSly8H">STS-82</a> servicing mission added capability in the <a href="/facts/Near_infrared/44XdJNcc">near-infrared</a> range, and in 2009 the <a href="/facts/STS-125/epWDLLKH">STS-125</a> servicing mission refurbished the telescope and extended its projected service life. It remains in active operation as of October 2024<a href="https://en.wikipedia.org/w/index.php?title=Great_Observatories_program&action=edit">[update]</a>.
The <a href="/facts/Compton_Gamma_Ray_Observatory/XrhShxVh">Compton Gamma Ray Observatory</a> (CGRO) primarily observed <a href="/facts/Gamma_ray/5Drf913J">gamma rays</a>, though it extended into <a href="/facts/Hard_x-ray/wseP79cN">hard x-rays</a> as well. It was launched in 1991 aboard <a href="/facts/Space_Shuttle_Atlantis/3NQUThEB">Atlantis</a> during <a href="/facts/STS-37/Bf9bUKHA">STS-37</a>. It was <a href="/facts/Atmospheric_entry/p7TMk9sa">de-orbited</a> in 2000 after a gyroscope failed.
The <a href="/facts/Chandra_X-ray_Observatory/zU89xG3a">Chandra X-ray Observatory</a> (CXO) primarily observes <a href="/facts/Soft_X-ray/wseP79cN">soft X-rays</a>. It was launched in 1999 aboard <a href="/facts/Space_Shuttle_Columbia/uF51RXWM">Columbia</a> during <a href="/facts/STS-93/SctNlqnB">STS-93</a> into an elliptical high-Earth orbit, and was initially named the Advanced X-ray Astronomical Facility (AXAF). It remains in active operation as of October 2024<a href="https://en.wikipedia.org/w/index.php?title=Great_Observatories_program&action=edit">[update]</a>.
The <a href="/facts/Spitzer_Space_Telescope/Ic1xXIYb">Spitzer Space Telescope</a> (SST) observed the <a href="/facts/Infrared/44XdJNcc">infrared</a> spectrum. It was launched in 2003 aboard a <a href="/facts/Delta_II_rocket/GoBa3Qch">Delta II rocket</a> into an Earth-trailing solar orbit. Depletion of its <a href="/facts/Liquid_helium/JYXCAcDf">liquid helium</a> coolant in 2009 reduced its functionality, leaving it with only two short-wavelength imaging modules. It was removed from service and placed into safe-mode on January 30, 2020.

Great Observatories program open-in-new

Great Observatories program