The Agena Target Vehicle was designed to develop and practice orbital rendezvous and docking in space, in preparation for the lunar mission.
The ATV consisted of the Lockheed Agena spacecraft and the McDonnell docking adapter. The Agena was launched from AMR (Cape Canaveral) Complex 14 on top of a Convair Atlas booster. The Agena first burn would occur shortly after shroud jettison and separation from the Atlas over the Atlantic Ocean. Over Ascension Island, a second burn would boost the Agena into a low circular orbit.
The McDonnell Gemini spacecraft would then launch (as close as 90 minutes) from Complex 19 (both countdowns would proceed in parallel and required close synchronization) and, toward the end of the program, would dock with the Agena within the first orbit after launch.
The Gemini astronauts would then fly in a stabilized mode and perform a number of experiments:
- letting the Agena stabilize the formation to save the capsule's propellants (on the first docking, a stuck nozzle on the capsule resulted in an emergency undock and the mission termination)
- EVA and work on a tool panel (this required installing handrails on the next flight after one astronaut's heart rate exceeded safe limits due to the effort expended just holding on)
- lighting the Agena engine and reaching an altitude of 400 miles (a human record at the time)
- undocking, unreeling a 100 nylon strap between the capsule and the Agena and flying in a "dumbbell" configuration with the Agena below the astronauts (to check the gravitational effect on the formation stability in uncontrolled mode. This is now known as gravity gradient stabalization.)
- using a similar teather and a few thruster bursts to rotate the two craft around each other as an early test of artificial gravity.
