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Feasibility study of calotte enclosure for Cornell Caltech Atacama Telescope

Cornell University and California Institute of Technology are currently studying the feasibility of constructing a 25 meter telescope to operate down to 200 micron wavelength to be sited on a high peak in the Atacama region of Chile. An enclosure dome is required to protect the telescope from wind, solar heating, snow, and dust. A diameter of 50 meters at the equator is anticipated, larger than any existing opening telescope enclosure. A review of various approaches indicates that a "calotte" type design, which uses two rotational axes to achieve full sky pointing, is structurally and dynamically superior to other large enclosure approaches. The calotte design is balanced about both axes of rotation and features a circular aperture which provides optimal isolation from the wind. The nearly continuous spherical shell lends itself to efficient space frame type structural form. An initial conceptual design was developed, including structures, bearings, and drive systems. Analysis of these components was performed which illustrates the feasibility of the chosen approach and provides indications of areas of critical risk in further development.