Giant Magellan Telescope site testing seeing and turbulence statistics

Cerro Las Campanas located at Las Campanas Observatory 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. 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 have been collected. Co. Las Camapanas and the Magellan site are nearly identical in their seeing statistics, and apparently their average ground-layer characteristics.