Canyon was the first series of NRO's near geostationary ELINT/SIGINT satellites launched under the designation AFP-827 or Program 7500. They were focussed on communications intelligence (COMINT).
The satellites were primary built to intercept soviet communications transmissions, especially line-of-sight microwave links, but were also able to tap into very high frequency (VHF) communications. Main contractor was Lockheed. Reportedly they consisted of a large (ca. 10 m diameter) antenna and were three axis stabilized. They were deployed into a 24 h orbit, which is not geostationary, so that triangulations of emmiter sources can be made from different points.
As the orbital data reported is not quite consistent, it is unclear, if the Canyons were deployed directly into the final orbit by the Agena-D or if they used a apogee kick motor. Recent analysis by Jonathan McDowell hints to the first theory, with the Agena-D remaining attached to the spacecraft during the first three missions.
The first satellite was successfully launched in August 1968, but was lost soon after reaching it's station due to erroneous commands sent by ground control. The next two satellites became operational in orbit, but suffered both from service outages. The fourth was lost in a launch failure. The final three satellites eventually performed better and produced valuable intelligence data.
They were succeeded by the Chalet / Vortex series.
|Type / Application:||ELINT|
|Configuration:||~ 10 m Ø Dish Antenna, 3-Axis-Stabilization|
|Orbit:||30200 km × 40800 km, 9.00° (typical)|
|Canyon 1 (7501, OPS 2222)||1968-063A||06.08.1968||CC LC-13||Atlas-SLV3A Agena-D|
|Canyon 2 (7502, OPS 3148)||1969-036A||13.04.1969||CC LC-13||Atlas-SLV3A Agena-D|
|Canyon 3 (7503, OPS 7329)||1970-069A||01.09.1970||CC LC-13||Atlas-SLV3A Agena-D|
|Canyon 4 (7504)||1971F||04.12.1971||CC LC-13||F||Atlas-SLV3A Agena-D|
|Canyon 5 (7505, OPS 9390)||1972-101A||20.12.1972||CC LC-13||Atlas-SLV3A Agena-D|
|Canyon 6 (7506, OPS 4966)||1975-055A||18.06.1975||CC LC-13||Atlas-SLV3A Agena-D|
|Canyon 7 (7507, OPS 9751)||1977-038A||23.05.1977||CC LC-13||Atlas-SLV3A Agena-D|