Proceedings Article | 6 August 2010
Proc. SPIE. 7733, Ground-based and Airborne Telescopes III
KEYWORDS: Telescopes, Mirrors, Scattering, Cameras, Sensors, Spectrometers, Reflectivity, Wavefronts, Space telescopes, Relays
CCAT will be a 25 m diameter, submillimeter-wave telescope. It will be located on Cerro Chajnantor in the
Atacama Desert, near ALMA. CCAT will be an on-axis, Ritchey-Chrétien design with an active primary to
compensate gravitational deformations. The primary mirror will have 162 segments, each with ~0.5 × 0.5 m
reflecting tiles on a ~2×2 m, insulated, carbon-fiber-reinforced-plastic subframe. CCAT will be equipped with
wide-field, multi-color cameras and multi-object spectrometers at its Nasmyth foci. These instruments will cover
all the atmospheric windows in the λ = 0.2 to 2 mm range. The field of view at the Nasmyth foci will be 1°,
so CCAT will be able to support cameras with a few ×104 detectors (spaced 2 beamwidths) at λ = 1 mm to
a few ×106 detectors (spaced half a beamwidth) at λ = 350 μm. Single instruments of this size are probably
impractical, so we will break the field into smaller pieces, with a separate sub-field camera for each piece. The
cameras will require some relay optics to couple the fairly slow beam from the telescope to the detectors. A
reflective relay for 1° field of view is too large to be practical, so we plan to use a compact, cold, refractive relay
in each sub-field camera.
