The beam reflected off a Gregorian secondary to a flat tertiary mirror with a fourth flat mirror directing it to a Coudé focus below the telescope (in the AST/RO building) along the azimuth axis. AST/RO also had a Nasymth focus accessed by the removal of the fourth mirror. Over its lifetime, AST/RO observed with five heterodyne receivers. These receivers operated at 230 GHz, 450-495 GHz (two), 800-820 GHz, and an array of four 800-820 GHz. AST/RO was able to process seven intermediate-frequency bandpasses using acousto-optical spectrometers. These included two low resolution spectrometers with a 1 GHz bandwidth, an array of four low-resolution spectrometer channels with a 1 GHz bandwidth, and a high-resolution spectrometer with a 60 MHz bandwidth. Science AST/RO was designed to carry out the first survey of the southern Galactic Plane, high-latitude clouds, and the Magellanic Clouds in the emission lines of neutral atomic carbon (CI) at 492 and 809 GHz. In its early years, observations focused on site characterization at 492 and 230 GHz. Regular sky dips at 492 GHz demonstrated that the South Pole is the best submillimeter-wave observatory site on Earth. Notable scientific achievements of AST/RO include: Mapping dense molecular gas in star-forming regions of the Magellanic clouds. Multifrequency study of the properties of interstellar star-forming clouds and their interactions with HII regions and supernovae. Determination of the thermodynamic state of dense gas within the central few kiloparsecs of the Milky Way. Physical state of high-latitude (out of the plane of the Milky Way) translucent molecular clouds. Terahertz detection of N II and its mapping in the Eta Carina region. See also List of astronomical observatories Lists of telescopes Rodney Marks (astrophysicist) References External links Antarctic Submillimeter Telescope and Remote Observatory (AST/RO) on the internet Submillimetre telescopes Astronomical telescopes and observatories in the Antarctic 1994 establishments in Antarctica 2005 disestablishments in Antarctica