James Crawford, NASA lead U.S. scientist for Korea United States-Air Quality (KORUS-AQ) Experiment, explains goals for the KORUS-AQ experiment at Osan Air Base, Republic of Korea, April 29, 2016. KORUS-AQ will deepen our understanding of the processes controlling air quality, improve knowledge of the challenges facing satellite observations of air quality and improve the ability of models to forecast and assess air quality conditions.(U.S. Air Force photo by Staff Sgt. Jonathan Steffen/Released)