The first large US signals intelligence satellite. Placed into near-geosynchronous orbits. They were misidentified by some analysts as missile warning satellites.

Total Mass: 700 kg.

First launch in a communications intelligence program operated by the USAF within the National Reconnaissance Office, on behalf of the National Security Agency. The first generation series, CANYON, was based on the Agena vehicle. The Agena D remained attached to the spacecraft.

First launch of improved ELINT satellite. In comparison to earlier Canyon ELINT satellites, Improved Canyon had a similar but heavier payload which separated from the Agena D final stage.

• 126 - Bramscher, Robert G, Spaceflight, "A Survey of Launch Vehicle Failures", 1980, Volume 22, page 351.
• 172 - McDowell, Jonathon, Quest, "US Reconnaissance Satellite Programs Part 2", 1995, Volume 4, Issue 4, page 49.