But the engineers could stave off the inevitable only so long: In February 1963 accumulating radiation damage finally caused Telstar 1's transistors to fail irreparably. Fortunately, the energized electrons had dissipated when NASA launched Telstar 2 a year later. By that time both the U.S. and Soviet Union had ceased high-altitude nuclear testing.
*Clarification (7/11/12): This sentence was changed after posting. It originally stated that the first transatlantic telephone call was made via Telstar 1.