Question: The Pahute Mesa's southeast region lies in what was formerly known as what?
Sentence (from "Nevada Test Site"): The Nevada National Security Site (N2S2),(though the abbreviation NNSS is still used), previously the Nevada Test Site (NTS), is a United States Department of Energy reservation located in southeastern Nye County, Nevada, about 65 miles (105 km) northwest of the city of Las Vegas.
Relevant evidence: No