ATDA

ATDA [NASA]

The ATDA (Augmented Target Docking Adapter) had been prepared as a back-up target in case of an GATV (Gemini Agena Target Vehicle) failure. The ATDA was a short cylinder consisting of a target docking adapter cone mounted on front and containing a communications system, a guidance and control system, and a reaction control system. It also had running lights, but unlike the GATV, the ATDA had no propulsive capabilities for orbit changes.

The ATDA was launched from Cape Canaveral using an Atlas-SLV3 rocket without upper stage after the GATV target for Gemini 9 was lost in an launch failure. The spacecraft was successfully injected into a near-circular 304 km orbit, but telemetry signals indicated that the launch shroud, which covered the docking adaptor, had separated but had not been jettisoned. This was confirmed when Gemini 9 was launched two days later and the astronauts observed the launch shroud still on the ATDA blocking the docking port, looking, according to Tom Stafford, like an "angry alligator". Rendezvous within 8 meters of the ATDA was achieved by Gemini 9 on the third revolution. The shroud had not jettisoned because the lanyards had been installed improperly with the loose ends taped down, due to "insufficiently detailed" instructions. Plans to cut the fiber glass shroud loose were considered but discarded as too dangerous to the astronauts. The flight plan was then revised and Gemini 9 completed two different equiperiod rendezvous maneuvers with the ATDA.