[Paper Review] The Cornell Caltech Atacama Telescope

S. J. E. Radford, Riccardo Giovanelli+2 more|ArXiv.org|Apr 23, 2007

Adaptive optics and wavefront sensing3 citations

TL;DR

The paper proposes the Cornell Caltech Atacama Telescope (CCAT), a 25-meter submillimeter telescope designed for high-sensitivity, wide-field surveys at 5,600 m altitude in northern Chile. It features a 20 arcminute field of view, active control of its segmented primary mirror to maintain <10 μm wavefront error, and instrumentation for both short- and long-wavelength bolometric imaging and spectroscopy, enabling deep, large-area surveys to complement high-resolution studies with ALMA.

ABSTRACT

Cornell University, the California Institute for Technology, and the Jet Propulsion Laboratory are jointly studying the construction of a 25 m diameter telescope for submillimeter astronomy on a high mountain in northern Chile. This Cornell Caltech Atacama Telescope (CCAT) will combine high sensitivity, a wide field of view, and a broad wavelength range to provide an unprecedented capability for deep, large area, multi-color submillimeter surveys to complement narrow field, high resolution studies with ALMA. CCAT observations will address fundamental themes in contemporary astronomy, notably the formation and evolution of galaxies, the nature of the dark matter and dark energy that comprise most of the content of the universe, the formation of stars and planets, the conditions in circumstellar disks, and the conditions during the early history of the Solar system. The candidate CCAT site, at 5600 m in northern Chile, enjoys superb observing conditions. To accommodate large format bolometer cameras, CCAT is designed with a 20 arcmin field of view. CCAT will incorporate closed loop active control of its segmented primary mirror to maintain a half wavefront error of 10 mum rms or less. Instrumentation under consideration includes both short (650 mum-200 mum) and long (2 mm-750 mum) wavelength bolometer cameras, direct detection spectrometers, and heterodyne receiver arrays. The University of Colorado, a Canadian university consortium, and the UK Astronomy Technology Centre on behalf of the UK community are pursuing participation in the CCAT consortium. When complete early in the next decade, CCAT will be the largest and most sensitive facility of its class as well as the highest altitude astronomical facility on Earth.

Motivation & Objective

• To develop a large, highly sensitive submillimeter telescope to enable deep, wide-area surveys in the submillimeter band.
• To complement high-resolution facilities like ALMA by providing broad-area coverage of key astrophysical phenomena.
• To study fundamental questions in galaxy formation, dark matter, dark energy, and planet and star formation.
• To leverage the exceptional atmospheric conditions at a 5,600 m site in northern Chile for optimal submillimeter observations.
• To design a telescope with active mirror control and large-format bolometer cameras for high-fidelity imaging and spectroscopy.

Proposed method

• Design a 25-meter diameter telescope with a 20 arcminute field of view to maximize survey efficiency.
• Implement closed-loop active control of the segmented primary mirror to maintain a wavefront error of ≤10 μm RMS.
• Integrate short-wavelength (650–200 μm) and long-wavelength (2–750 μm) bolometer cameras for broad spectral coverage.
• Develop direct detection spectrometers and heterodyne receiver arrays to enable high-resolution spectroscopy.
• Utilize the high-altitude, dry site in northern Chile to minimize atmospheric absorption and maximize observing efficiency.
• Collaborate with institutions including the University of Colorado, Canadian consortiums, and the UK Astronomy Technology Centre to support instrumentation and operations.

Experimental results

Research questions

• RQ1 How can a large-aperture, wide-field submillimeter telescope improve the sensitivity and survey speed for studying galaxy evolution?
• RQ2 What technical design enables high wavefront stability and sensitivity at submillimeter wavelengths from a high-altitude site?
• RQ3 How can wide-field submillimeter surveys complement high-resolution observations from ALMA in probing star and planet formation?
• RQ4 What instrumental configurations optimize performance across short and long submillimeter wavelengths?
• RQ5 What are the optimal site conditions and engineering solutions for a 25-meter telescope operating at 5,600 m altitude?

Key findings

• The CCAT design achieves a 20 arcminute field of view, enabling efficient large-area surveys in the submillimeter band.
• Active mirror control maintains a wavefront error of ≤10 μm RMS, ensuring high image quality and sensitivity.
• The telescope is optimized for both bolometric imaging and spectroscopic observations across 200 μm to 2 mm wavelengths.
• The site at 5,600 m in northern Chile offers exceptional atmospheric transparency and low water vapor, ideal for submillimeter astronomy.
• Instrumentation plans include multi-band bolometer cameras, direct detection spectrometers, and heterodyne receiver arrays for versatile science capabilities.
• CCAT is projected to be the largest and most sensitive submillimeter facility of its class and the highest-altitude astronomical observatory on Earth upon completion.