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. In 1997 the STS-82 servicing mission added capability in the near-infrared range, and in 2009 the STS-125 mission fixed the telescope and extended its projected service life. The Compton Gamma Ray Observatory (CGRO) primarily observed gamma rays, though it extended into hard x-rays as well. It was launched in 1991 aboard Atlantis during STS-37 and was de-orbited in 2000 after a gyroscope failed. The Chandra X-ray Observatory (CXO) primarily observes soft X-rays. It was launched in 1999 aboard Columbia during STS-93 into an elliptical high-Earth orbit, and was initially named the Advanced X-ray Astronomical Facility (AXAF). The Spitzer Space Telescope (SST) observed the infrared spectrum. It was launched in 2003 aboard a Delta II rocket into an Earth-trailing solar orbit. Depletion of its liquid helium 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 The Hubble Space Telescope and Chandra X-ray Observatory continue to operate as of April 2022. Hubble was originally intended to be retrieved and returned to Earth by the Space Shuttle, but the retrieval plan was later abandoned. On 31 October 2006, NASA Administrator Michael D. Griffin gave the go-ahead for a final refurbishment mission. The 11-day STS-125 mission by Space Shuttle Atlantis, launched on 11 May 2009, installed fresh batteries, replaced all gyroscopes, replaced a command computer, fixed several instruments, and installed the Wide Field Camera 3 and the Cosmic Origins Spectrograph. One of the three gyroscopes on the Compton Gamma Ray Observatory failed in December 1999. Although the observatory was fully functional with two gyroscopes, NASA judged that failure of a second gyroscope would result in inability to control the satellite during its eventual return to Earth due to orbital decay. NASA chose instead to preemptively de-orbit Compton on 4 June 2000. Parts that survived reentry splashed into the Pacific Ocean. Spitzer was the only one of the Great Observatories not launched by the Space Shuttle. It was originally