The ATST site survey goal was to locate a site that would maximize the scientific productivity of the telescope. The general daytime characteristics of such a site are frequently clear skies, excellent seeing, low humidity, few aircraft contrails, and low dust levels. The ATST project developed instrumentation to measure the relevant atmospheric characteristics, and placed a set of instruments at six candidate sites.

In December 2004, Haleakalā, Hawai'i was recommended as the best site for ATST.