Astronaut Bruce McCandless II approaches his maximum distance from the Earth-orbiting Space Shuttle Challenger in this 70mm photo from Feb. 7, 1984. While testing out the nitrogen-propelled, hand-controlled back-pack device called the manned maneuvering unit (MMU) for the first time, McCandless’s fellow crewmembers aboard the reusable vehicle photographed him. The MMU allowed crews to move outside of the cargo bay and perform activities away from the safety of the spacecraft. “It may have been one small step for Neil,” he proclaimed, “but it’s a heck of a big leap for me.”

Learn how this and other iconic photos from the STS-41B mission came to be.

Image Credit: NASA