Tracking and command of the GATV were also aided by a rendezvous beacon, two spiral L-band antennas, two tracking antennas (C-band and S-band), two VHF telemetry antennas, and a UHF command antenna. A 2.1 meter long retractable L-band boom antenna extended from the side of the cylinder near the front. Acquisition running lights and target vehicle status display indicators were situated on the front end. The docking cone was connected to the front end by shock absorbing dampers. A minimum of five engine starts was possible. The Agena propulsion systems could be run while the Gemini was docked, allowing the GATV to be used to change the orbit of the docked pair. Propulsion was via a bi-propellant system, using unsymmetrical dimethylhydrazine (UDMH) and inhibited red fuming nitric acid (IRFNA). The primary and secondary propulsion systems were at the aft end of the target vehicle with the attitude control gas tanks, and the main propellant (fuel and oxidizer) tanks were located in the mid-section.

The forward section of the Agena airframe held the guidance, flight control electronics, telemetry, command, tracking, electrical power, and propellant pressurization equipment.

At launch it carried 6375 kg of propellant and gas. The GATV was a 7.93 meter long cylinder with a diameter of 1.52 meters and a dry mass of 1834 kg. The GATV had a docking cone at the forward end into which the nose of the Gemini spacecraft could be inserted and held with docking latches. The Gemini Agena Target Vehicle was designed to be launched into Earth orbit prior to a Gemini mission and used for rendezvous and docking practice. Later investigation concluded the most likely cause of the failure was a hard start and explosion caused by fuel preceding oxidizer into the thrust chamber during ignition. The Gemini 6 launch, scheduled to occur 101 minutes later, was cancelled. Shortly afterwards radar at Patrick AFB reportedly 'picked up 5 pieces' of debris at the point in space the Agena was supposed to be.

Just before loss of contact telemetry showed a marked rise in pressure in both propellant tanks. All attempts to reestablish contact or radar track with the vehicle failed. At 10:05:10 a.m., 5:06 after launch, the Agena separated from the Atlas successfully and all signals were normal, but 368.4 seconds after launch, at initiation of Agena target vehicle primary propulsion system firing for Earth orbit insertion, an anomaly occurred and telemetry and radar beacon track were lost 7 seconds later. EST (15:00:04 UT) on an Atlas-Agena D rocket. The Gemini 6 Agena Target Vehicle (vehicle GATV 5002) was launched from Cape Canaveral on 25 October 1965 at 10:00:04 a.m.

Agena spacecraft