 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.