In 1959, CIA’s Office of ELINT was briefed on the Intelligence Community’s concern that the Soviets might be constructing antiballistic missiles or radars to track or even interfere with the US tracking of the DISCOVERER satellites. CIA decided that a small, self-contained electronic payload attached to the aft rack of the DISCOVERER Agena vehicle would be capable of detecting any Soviet tracking or interference with the S-band beacon used on the Agena vehicle. The experiments were approved in November 1959 and, given their location on the vehicle, became known as AFTRACK payloads. The goal was to build systems that could be developed in less than nine months that could operate reliably for a long enough period of time to answer urgent intelligence questions and provide input to the design of collection systems then under development. AFTRACK became known as “vulnerability” payloads because of their part in an NRO program to determine the susceptibility of reconnaissance satellites to hostile Soviet activities.
The first AFTRACK was called SOCTOP. It was mounted on the aft rack of the DISCOVERER 13 Agena vehicle successfully launched on 10 August 1960. The AFTRACK effort concluded with DONKEY launched on 24 July 1967. Payload configurations over this period of time changed as new and improved tracking radars appeared and as collection payload technology improved. Contributions of the AFTRACK payloads included revealing a high density of Soviet radars, monitoring Soviet radar tracking of US reconnaissance satellites, and producing the locations of Soviet communications transmitters.
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