Gumdrop Meets Spider
Apollo 9 astronaut Dave Scott stands in the open hatch of the Command Module "Gumdrop," docked to the Lunar Module "Spider" in Earth orbit. His crewmate Rusty Schweickart took the photo. Along with Jim McDivitt, Scott and Schweickart tested out the orbital rendezvous and docking procedures that made the lunar landings possible.
Image Credit: NASA