Apollo 10 crew left to right, Eugene Cernan, Thomas Stafford and John Young. Credit: NASA
Launched from Cape Kennedy on May 18, 1969, Apollo 10 was the fourth manned Apollo mission launched in seven months, and it became the second spacecraft to orbit the moon. Its crew was Commander Thomas Stafford, Lunar Module Pilot Eugene Cernan, and Command Module Pilot John Young. Mission objectives were to gather data on lunar potential, and test the lunar module's programmed trajectories, radar, and flight control systems to prepare for an eventual Moon landing.
Apollo 10 on the landing pad at Cape Kennedy, May 1969. Credit: NASA
After exiting the Earth's atmosphere, Apollo 10 was set on a trajectory to reach the Moon. The command/service module separated, then docked itself to the lunar module before they began their trip. Young remained in the command module, code-named Charlie Brown, while Stafford and Cernan entered the lunar module, code-named Snoopy. Three days later Apollo 10 reached the Moon where Stafford and Cernan descended in the lunar module orbiting approximately nine miles above the lunar surface.
Earthrise as seen from Apollo 10. Credit: NASA
The mission was a success, but it didn't go off without a hitch. When the ascent engine was ignited to send the lunar module away from the lunar surface, duplicated commands to the flight computer caused the spacecraft to roll violently, but control was restored after 8 rolls. The crew re-entered Earth's atmosphere and splashed down in Pacific Ocean on May 26, 1968. The total flight time was 192 hours, 3 minutes, and 23 seconds. During the mission, the astronauts obtained hundreds of still photographs and reels of film. Apollo 10 was an important mission for NASA astronauts to perform a "dress rehearsal" for the eventual Apollo 11 moon landing.