DULLES, Va.--(BUSINESS WIRE)--Orbital ATK, Inc. (NYSE:OA), a global leader in aerospace and defense technologies, today announced a major milestone in a deep space exploration mission aimed at uncovering the mysteries of the solar system. NASA’s Dawn spacecraft has arrived at and is now orbiting the dwarf planet Ceres. Dawn, designed and built by Orbital ATK, accomplished this feat with the innovative use of solar electric ion propulsion, the world’s most advanced and efficient space propulsion