The Arecibo Observatory in Arecibo, Puerto Rico, is owned by the U.S. government. The Arecibo radio telescope dish is a breathtaking sight. Nestled between hills, on top of a natural valley in the land, it is 1,000 feet (305 meters) in diameter and covers an area of more than twenty-five football fields. Its Gregorian reflector system is at the focal point of the radio telescope, weighs seventy-five tons, and hangs 450 feet (137 meters) in the air; it is attached to a much larger, six-hundred-ton observing platform, which also hangs there in midair.

Arecibo is by far the world’s largest radio dish, and it is also the most sensitive radio telescope in the world, since its completion in 1963. It has stayed current with regular upgrades to its instrumentation and equipment, and is used day and night for scientific observations and, occasionally, communications with spacecraft far out in the solar system.