Echo I

Echo I was the world's first passive communications satellite, launched into an Earth orbit on August 12, 1960. It was simply a large metallic-coated Mylar balloon, 100ft in diameter, that allowed microwave signals to be reflected off of its surface. Signals were sent from one place on Earth and received at another location. It also permitted other scientific experiments and, notably, it allowed the exact location of Moscow to be calculated, in case inter-continental ballistic missiles needed to be launced during the Cold War. This stamp was issued on December 15, 1960 to honor Echo I.