During much of the Cold War, America's first line of defense was in outer space: a network of secret satellites that could provide instant warning of an enemy missile launch. The presence of these infrared sensors orbiting 22,000 miles above the earth discouraged a Soviet first strike and stabilized international relations between the superpowers, and they now play a crucial role in monitoring the missile programs of China, India, and other emerging nuclear powers. Jeffrey Richelson has written the first comprehensive history of this vital program, tracing its evolution from the late 1950s to the present. He puts Defense Support Program operations in the context of world events - from Russian missile programs to the Gulf War - and explains how DSP's infrared sensors are used to detect meteorites, monitor forest fires, and even gather industrial intelligence by "seeing" the lights of steel mills.