Canyon was a series of seven United States spy satellites launched between 1968 and 1977. Also known by its program number AFP-827, the satellites were developed with the participation of the Air Force. The Canyon project is credited as being the first American satellite system tasked for COMINT. The satellites each had a mass of 700 kg and were launched from Atlas/Agena D rockets into near-geosynchronous orbits. They carried large parabolic reflecting dishes, estimated at 10m in diameter, and signals were transmitted to a center in Bad Aibling, West Germany. The Canyon satellites were eventually replaced with the next generation of COMINT satellites, the Vortex/Chalet series. Unlike contemporary photo-reconnaissance satellites, Canyon was not a bus satellite integrated into the Agena stage and it separated once placed in geostationary orbit. The program is still classified. Seven Canyon satellites were launched from 1968 to 1977, all with Atlas SLV-3A (extended Atlas tanks for longer burn time) Agena D vehicles from LC-13 at Cape Canaveral rather than Vandenberg Air Force Base, due to the necessity of placing them in a geostationary orbit. The first Canyon was launched on August 6, 1968. Secrecy surrounding the satellite was tight, and the Air Force would say nothing other than that an "experimental payload" had been launched and it was the first "secret" launch conducted from the Cape since 1963. After a successful launch and orbital deployment, the satellite's mission ended disastrously when a ground controller sent an erroneous command that sent it into an unrecoverable tumble. The second Canyon was launched in April 1969, followed by the third in September 1970. Both satellites performed erratically, with their transmissions often cutting out or becoming intermittent. Despite these problems Canyons 2 and 3 returned much useful intelligence information, particularly regarding Chinese military maneuvers during the winter of 1970-71 when tensions between China and the USSR were at an all-time high, and also intelligence on North Vietnam for the 1972 Christmas Bombing campaign. The fourth Canyon, launched on December 4, 1971, never made it to orbit. The Atlas booster's sustainer engine shut down early in the launch and the booster drifted off its path, leading to a Range Safety destruct less than two minutes after liftoff. The weather on launch day was extremely wet, foggy, and overcast, thus the booster had been out of visibility when the failure happened and the Air Force did not make an announcement for