with the space race and the cold war, the americans returned in 1956. wideawake airfield expanded in the mid-1960s. the runway, with its strange hump, was extended, widened, and improved to allow its use by large aircraft, and later to act as an emergency runway for the space shuttle, although the shuttle never had to use it. at the time, it was the world's longest airport runway. the united states air force used the island as part of its eastern range. nasa established a tracking station on the island in 1967, which it operated for more than 20 years before closing it down in 1990. a joint government communications headquarters and national security agency signals intercept station was also established on ascension during the cold war. the island retains a role in space exploration: the european space agency now operates an ariane monitoring facility there. the bbc atlantic relay station was installed in 1966 for short-wave broadcasts to africa and south america.