Here's a couple more short clips of the Apollo 9 mission. One shows the Command and Service Module, 'Gumdrop', orbiting with the hatch open, allowing EVAs to be performed around the spacecraft. The other features the Lunar Module, 'Spider', being tested in Earth orbit. This mission was the first time a manned 'pure' spacecraft had been tested in space. By that I mean that the Lunar Module had no capacity to serve as a viable re-entry vehicle to Earth. It was built only to operate in space and in a low gravity environment like the Moon.
The astronauts took Spider out to over a hundred miles away from the Command and Service Module, using the Lunar descent engine to travel out, and the Lunar ascent engine to return. The film clearly shows the ascent stage of the LM (minus the LM descent stage with it's landing legs) returning to rendezvous with the CSM. The crew then successfully re-docked with the CSM. That's proper test pilot stuff.
Having rehearsed and proved the major procedures of undocking, free flight, rendezvous and redocking, the next time U.S. astronauts would perform the feat would be a quarter of a million miles away whilst orbiting the Moon.
That test, amongst many others would take place on the Apollo 10 mission, scheduled for May 1969.
