Canyon (satellite)

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. The Canyon satellites were eventually replaced with the next generation of COMINT satellites, the Vortex/Chalet series. 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. There was one failure when the fourth Canyon was launched on December 4, 1971. The Atlas's sustainer engine shut down shortly after launch and it wandered off course, leading to a Range Safety destruct. Since the failure took place behind cloud cover (the weather on December 4 was damp, foggy, and overcast), it was not visible from the ground and so the Air Force waited two days to make an announcement.

The failure of Canyon 4 created some delay as NASA had intended to launch an Intelsat on an Atlas-Centaur the following day, but decided to wait until the Air Force investigation was completed, since the two booster types were extremely similar. The Intelsat was not launched until December 20.

The first four Canyons apparently remained attached to the Agena after achieving orbit, using its engine for maneuvering (the missions would have been concluded after Agena propellant depletion). Later Canyons were reputedly larger in size and did separate from the booster.

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