Gemini 6A was the fifth crewed Earth-orbiting spacecraft of the Gemini series, having been launched after Gemini 7, with the intent of making rendezvous with Gemini 7 in Earth orbit. The astronauts on the 26 hour mission were Walter Schirra and Thomas Stafford. The mission priorities were to demonstrate on-time launch procedures, closed-loop rendezvous capabilities, and stationkeeping techniques with Gemini 7. Other objectives were to evaluate the spacecraft reentry guidance capabilities, and conduct spacecraft systems tests and four experiments. This mission was originally designated Gemini 6 and scheduled for launch on 25 October but was cancelled when the Agena target vehicle failed to go into orbit an hour earlier.
Gemini 6A was scheduled to launch on 12 December 1965, but the launch was aborted one second after engine ignition because an electrical umbilical separated prematurely. This was the first time an astronaut mission was aborted after ignition start. The mission launched successfully from Complex 19 on 15 December at 8:37:26 a.m. EST (13:37:26.471 UT) and was inserted into a 161.0 x 259.4 km orbit at 8:43:25. At this point Gemini 6A trailed Gemini 7 by about 1900 km. Four major thruster burns were performed starting at 9:11 to catch up to Gemini 7. First radar lock indicated a distance of 396 km. Two more major thruster burns preceded the final braking maneuver at 2:27 p.m. EST. Rendezvous was technically achieved and stationkeeping begun at 2:33 with the two Gemini spacecraft in zero relative motion at a distance of 110 meters. Stationkeeping maneuvers involving the spacecraft circling each other and approaching and backing off continued for 5 hours 19 minutes over three and a half orbits. During the maneuvers, all four astronauts on both spacecraft took turns in the formation flying activities and photographs were taken from both spacecraft. This marked the first time two spacecraft were maneuvered with respect to each other by their crews. At the end of stationkeeping Gemini 6 fired thrusters to move to a position roughly 50 km away from Gemini 7 for drifting flight during the sleep period.
Near the end of the 15th revolution the retrorockets were fired at 9:53:24 a.m. EST on 16 December and splashdown occurred at 10:28:50 at 23.58 N, 67.83 W only 13 km from the target. This was the first successful controlled reentry to a predetermined point in the U.S. manned spaceflight program. The spacecraft and crew were brought aboard the aircraft carrier U.S.S. Wasp at 11:32 a.m. The recovery and rendezvous section of the spacecraft splashed down in the same area and was retrieved, this was the first time the service section was recovered. Total mission elapsed time was 25:51:24.
All primary mission objectives were achieved. The only major malfunction was the failure of the delayed time telemetry tape recorder at 20 hours 55 minutes into the mission, resulting in loss of the last 4:20 of delayed time telemetry. The crew conducted three scientific experiments -- (1) synoptic terrain photography, (2) synoptic weather photography, and (3) dim light photography. The fourth experiment, measurement of radiation in spacecraft, was only partly completed.