Types of Observatories

The Compton Gamma Ray Observatory (CGRO) was the second of NASA's Great Observatories. Compton, at 17 tons, was the heaviest astrophysical payload ever flown at the time of its launch on April 5, 1991, aboard the space shuttle Atlantis.

SPACE.com compiled a list of the major observatories currently up doing space-based astronomy. The list excludes rovers, orbiters and planetary probes not doing traditional telescope observations. The list excludes rovers, orbiters and planetary probes not doing traditional telescope observations.

The European Southern Observatory (ESO) is a 15-nation intergovernmental research organization for ground-based astronomy. Created in 1962, ESO has provided astronomers with state-of-the-art research facilities and access to the southern sky.

The Gemini Observatory is an astronomical observatory consisting of two 8.19-metre (26.9 ft) telescopes, Gemini North and Gemini South, which are located at two separate sites in Hawaii and Chile, respectively.

The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. Founded in 1956, the NRAO provides state-of-the-art radio telescope facilities for use by the international scientific community.

The W. M. Keck Observatory is a two-telescope astronomical observatory at an elevation of 4,145 meters (13,600 ft) near the summit of Mauna Kea in the U.S. state of Hawaii. Both telescopes feature 10 m (33 ft) primary mirrors, currently among the largest astronomical telescopes in use.