关于这张图
S84-27018 (7 Feb 1984) --- Astronaut Bruce McCandless II approaches his maximum distance from the Earth-orbiting Space Shuttle Challenger in this 70mm frame photographed by his fellow crewmembers onboard the reusable vehicle. McCandless is in the midst of the first "field" tryout of the nitrogen-propelled, hand-controlled back-pack device called the manned maneuvering unit (MMU). Astronaut Robert L. Stewart got a chance to test the same unit a while later in the lengthy EVA session while the two spacewalkers were photographed and monitored by their fellow crewmembers in Challenger's cabin. …
