The augmented target docking adapter (ATDA) would serve as an alternative to the Gemini Agena target vehicle (GATV) if efforts to remedy the GATV problem responsible for the October 25 mission abort did not meet the date scheduled for launching Gemini VIII.

Using Gemini-qualified equipment, the ATDA (as its name implied) was essentially a target docking adapter (TDA) with such additions as were needed to stabilize it and allow the spacecraft to acquire and dock with it. In addition to the shroud and TDA, these included a communications system (comprising tracking, telemetry transmission, and command subsystems), instrumentation, a guidance and control system (made up of a target stabilization system and rendezvous radar transponder), electrical system, and a reaction control system identical to the Gemini spacecraft's. Robert C. Seamans, Jr., NASA Associate Administrator, approved the procurement of the ATDA on December 9, and McDonnell began assembling it December 14.