three days. The failure momentarily delayed the planned launch of an Atlas-Centaur with an Intelsat satellite until the Air Force Mishap Review Board could complete their investigation and relieve the Atlas-Centaur of guilt by association. A fuel line obstruction was suspected of having blocked the flow of propellants to the sustainer gas generator, and the way was cleared for the Intelsat launch, which took place on December 20. Three more Canyons were launched in 1972, 1975, and 1977, all of which performed well and gathered considerable intelligence on Soviet activities as well as Arab communications during the 1973 Yom Kippur War. Indeed, the amount of communications data returned was so voluminous that some of it took up to two years to sort through. The Air Force did not acknowledge the existence of the program at all until 1990, thirteen years after the last Canyon was launched. However, the Soviets found out about it as early as 1975 and began taking preventative measures to stop their radio communications from being tapped into, including the replacement of satellite dishes with landlines. In addition, Geoffrey Prime, a British member of the Government Communication Headquarters, had contacts with the KGB and funneled various information regarding US satellite intelligence, which may have included details on Canyon. The Canyon program was succeeded by Chalet/Vortex, whose maiden voyage took place in June 1978. List of Launches See also Rhyolite/Aquacade - Another SIGINT platform operated for the Central Intelligence Agency Vortex/Chalet - Canyon's successor Qianshou-3 - China's SIGINT satellites in GEO References External links Gunter's Space Page - information on Canyon Spy satellites of the NSA 1971 in spaceflight 1972 in spaceflight Satellites of the United States Air Force Reconnaissance satellites of the United States Signals intelligence Signals intelligence satellites National Reconnaissance Office satellites Military equipment introduced in the 1960s