Airman 1st Class Nathaniel Greene, 28th Communications Squadron ground radar maintenance technician, calibrates equipment during a weekly inspection at the radar tower center in Box Elder, S.D., Aug. 13, 2013. Calibration of this equipment is vital to air traffic controllers’ ability to provide an accurate real-time visual reference of aircraft positions, guaranteeing safety in the skies. (U.S. Air Force photo by Airman 1st Class Alystria Maurer/Released)