Gemini 8 launched on March 16, 1966, at 16:41:02 UTC from Launch Complex 19 atop a Titan II GLV. The crew was Command Pilot Neil Armstrong and Pilot David Scott — the first spaceflight for both.
Nearly seven hours earlier, at 15:00:03 UTC, the Agena Target Vehicle (GATV-5003) launched on an Atlas rocket. Armstrong docked with it at 23:14 UTC — the first-ever linkup of two spacecraft in orbit. Scott radioed Mission Control: "Flight, we are docked! Yes, it's really a smoothie" — the docking had gone smoothly.
The linked spacecraft remained docked for about half an hour. At approximately 23:45 UTC, the Agena executed a stored command to roll the combined vehicle 90°. Shortly after, Scott noticed the combined spacecraft was rolling uncontrollably — the start of the mission's most dramatic phase.
From the flight transcript
"Flight, we are docked! Yes, it's really a smoothie."
NASA — Gemini 8 Mission Report · NASA — On the Shoulders of Titans: A History of Project Gemini · NASA Image and Video Library — full list on Gemini 8