Design for CCAT, a 25 m diameter telescope operating from 200 GHz to 1.5 THz

CCAT will be a 25 m diameter Ritchey-Chretien telescope operating in the 0.2-1.5 mm wavelength range. It will be located at an altitude of 5600 m on Cerro Chajnantor in northern Chile, near the ALMA site. CCAT will have an f/0.4 primary, with an active surface to compensate gravitational and thermal deformations. The primary will be supported by a carbon fiber reinforced plastic (CFRP) space frame truss on an elevation over azimuth mount made of steel. Cameras and spectrometers with up to 1 deg field of view (FoV) will be located at the two f/6 Nasmyth foci. CCAT will be inside an enclosure to reduce wavefront and pointing errors due to wind forces and thermal deformation due to solar illumination. The key performance challenges for CCAT are a half wavefront error (HWFE) <;10 μm rms and pointing error <;0.2".