IQUIQUE, Chile -- Senior Airman Nelson Santiago, 23rd Special Tactics Squadron airfield systems technician, performs an hourly check on a portable tactical navigation aid, or TACAN, during SALITRE, a Chilean-led multinational exercise focused on interoperability between Chile, the United States, France, Argentina and Brazil. The TACAN allows U.S. F-15 pilots to locate the two operating airfields involved in SALITRE, and orient themselves for landing. The TACAN is typically used by combat controllers to establish airfields in austere environments, and this is the first time the 23rd STS has used them in an exercise of this nature. (U.S. Air Force photo/Tech. Sgt. Eric Petosky)