Chinese Ship Spooks Palau, Where U.S. Is Building Advanced Radar

OTH B big This diagram shows the basic concept of how the “backscatter” version of Over-the-Horizon radar works. Radar waves are bounced off the Earth’s ionosphere to radiate a large area of Earth’s surface up to 3,500 kilometers away. If the waves hit a ship or airplane, radio energy bounces back in all directions. A small part of this energy then returns to the radar’s receiver by moving in the opposite direction it came.