40 years ago today, Apollo 10 was launched into space. Commanded by Thomas P Stafford, this was the last pathfinder mission before Apollo 11 would land on the Moon two months later. This was a complete Apollo spacecraft with a command-service module called Charlie Brown flown by John W Young, and a lunar module called Snoopy flown by Eugene A Cernan. Gene Cernan was later to be the last man on the Moon when he commanded Apollo 17 and John Young would be the first shuttle commander.
Apollo 10 went to orbit the Moon where the astronauts tested the docking systems and flight characteristics of the lunar module. Lunar module Snoopy was flown down to an altitude of 15.6 km on 22nd May 1969. All the systems checked out and the go-ahead was given for Apollo 11 to make the first moon landing.
Apollo 10 returned safely to Earth on 26th May 1969, setting the speed record for a manned vehicle at 39,897 km/hr, unbroken to this day.
You can read more about the Apollo missions at NASA’s 40th anniversary site.