  The Atacama Large Aperture Submm Telescope (AtLAST) is a concept for a novel
50-meter class single-dish telescope operating at sub-millimeter and millimeter
wavelengths (30-950 GHz). The telescope will provide an unprecedentedly wide
field of view (FoV) of 1-2 degree diameter with a large receiver cabin housing
six major instruments in Nasmyth and Cassegrain positions. The high observing
frequencies, combined with the scanning operation movements with up to 3
deg/second, place high demands on the accuracy and stability of the optical and
structural components. The design features the introduction of a rocking chair
type mount with an iso-statically decoupled main reflector backup structure and
an active main reflector surface with a high precision metrology system. The
planned site location is in the Chilean Atacama Desert at approximately 5050
meters above sea level, near Llano de Chajnantor. This paper gives an overview
of the optical, structural, and mechanical design concepts. It explains the
flow-down from key science requirements to technical design decisions as well
as showing design analogies from other existing large radio, (sub-)mm, and
optical telescopes.
