Optical and mechanical design of the Antarctic Submillimeter Telescope and Remote Observatory

Antarctic Submillimeter Telescope and Remote Observatory ~AST/RO!, a 1.7 m diameter telescope for astronomy and aeronomy studies at wavelengths between 200 and 3000 mm, was installed at the South Pole during the 1994–95 Austral summer. The optical design is Gregorian, offset in both azimuth and elevation, with the exit pupil at the chopping tertiary mirror: this arrangement provides for consistent illumination of the primary mirror even when the beam is thrown one degree or more on the sky. Aberrations are minimized by the choice of secondary mirror offset angle. Alignment is accomplished by mechanical means. There is a Coudé focus in a warm, spacious receiver room and also a Nasmyth focus. Both the elevation and azimuth axes are driven by two pinion gears with opposed torques to eliminate backlash. The encoders are unusually robust but have high friction, necessitating a stiff coupling. The azimuth limit switch scheme permits 1.5 rotations, but the switches will operate under extreme conditions with no single point of failure. The instrument is now operational with four heterodyne receivers and three acousto-optical spectrometers. © 1997 American Institute of Physics. @S0034-6748~97!02805-0#