Great Observatories program

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NASA's series of Great Observatories satellites are four large, powerful space-based astronomical telescopes launched between 1990 and 2003. They were built with different technology to examine specific wavelength/energy regions of the electromagnetic spectrum: gamma rays, X-rays, visible and ultraviolet light, and infrared light. The Hubble Space Telescope (HST) primarily observes visible light and near-ultraviolet. It was launched in 1990 aboard the Space Shuttle Discovery during STS-31, but its main mirror had been ground incorrectly, resulting in spherical aberration that compromised the telescope's capabilities. The optics were corrected to their intended quality by the STS-61 servicing mission in 1993. In 1997, the STS-82 servicing mission added capability in the near-infrared range, and in 2009 the STS-125 servicing mission refurbished the telescope and extended its projected service life. It remains in active operation as of April 2026. The Compton Gamma Ray Observatory (CGRO) primarily...

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