GMT Site Evaluation at Las Campanas Observatory

The Giant Magellan Telescope project is in the fortunate position of having clear access to a developed site with a long history of excellent performance. Las Campanas Observatory has dark skies, little or no risk of future light pollution, excellent seeing, moderate winds and a high fraction of clear nights. Our site testing effort is concentrated on identifying the best peak within LCO in terms of seeing, turbulence profile, and wind speeds and on quantifying the potential impact of precipitable water vapor on GMT mid-infrared science goals by characterization in terms of both precision and time variability. Thus, we are measuring meteorological characteristics (pressure, temperature, humidity, wind, and cloud cover), seeing, the turbulence profile of the free atmosphere (above 500 m), precipitable water vapor, and light pollution at four sites within the LCO property.