Giant Magellan Telescope Site Testing Summary

TL;DR

This paper summarizes comprehensive site testing at Cerro Las Campanas in Chile for the Giant Magellan Telescope, demonstrating it meets all scientific and observational criteria necessary for optimal astronomical observations.

Contribution

It provides the first systematic comparison of meteorological and atmospheric turbulence data across potential GMT sites at LCO, confirming Cerro Las Campanas as the optimal choice.

Findings

Cerro Las Campanas has excellent seeing conditions.

The site has a high fraction of clear nights.

PWV levels are suitable for mid-IR astronomy.

Abstract

Cerro Las Campanas located at Las Campanas Observatory (LCO) in Chile has been selected as the site for the Giant Magellan Telescope. We report results obtained since the commencement, in 2005, of a systematic site testing survey of potential GMT sites at LCO. Meteorological (cloud cover, temperature, pressure, wind, and humidity) and DIMM seeing data have been obtained at three potential sites, and are compared with identical data taken at the site of the twin Magellan 6.5m telescopes. In addition, measurements of the turbulence profile of the free-atmosphere above LCO have been collected with a MASS/DIMM. Furthermore, we consider photometric quality, light pollution, and precipitable water vapor (PWV). LCO, and Co. Las Campanas in particular, have dark skies, little or no risk of future light pollution, excellent seeing, moderate winds, PWV adequate for mid-IR astronomy during a reasonable fraction of the nights, and a high fraction of clear nights overall. Finally, Co. Las Campanas meets or exceeds all the defined science requirements.