U.S. Air Force Staff Sgt. Robert Aten, 1st Combat Camera Squadron, documents a U.S. Army aircrew from the 7th Battalion, 158th Aviation Regiment as they conduct pre-flight checks aboard a UH-60 Black Hawk in order to be ready to leave at a moment's notice for a medical evacuation mission during Exercise Vibrant Response at Camp Atterbury, Ind., Aug. 19, 2011. Vibrant Response is the largest chemical, biological, radiological and nuclear (CBRN) response exercise designed to prepare expeditionary units focused on responding to domestic CBRN incidents.