NASA's series of Great Observatories satellites.

1. Hubble Space Telescope (HST) was called the Space Telescope (ST) before being named.
2. Compton Gamma Ray Observatory (CGRO) was called the Gamma Ray Observatory (GRO), before being named.
3. Chandra X-ray Observatory (CXO) was called the Advanced X-ray Astronomical Facility (AXAF), before being named. (aka, the Chandrasekhar Observatory).
4. Spitzer Space Telescope (SST) was called the Space Infra-red Telescope Facility (SIRTF), before being named.

NASA's follow-up Great Observatories program.

• James Webb Space Telescope (JWST) was called the Next Generation Space Telescope (NGST) before being named, and is the replacement for HST.
• Space Interferometry Mission (SIM)
• Terrestrial Planet Finder (TPF)

See also: Space observatory