NASA Abandoned A Spacecraft in Orbit for 5 Years. When It Came Home It Surprised Them!
NASA’s Long Duration Exposure Facility started out as a meteorite exposure payload, but evolved to look at every aspect of material changes on orbit, in particular by the time it was launched it was realised that one of the biggest threats in low Earth orbit is atomic oxygen which would slowly erode many common materials. The spacecraft was covered with experiments and was supposed to spend 12 months in orbit, instead because of delays and the Challenger disaster it spent 69 months in orbit and was weeks away from falling back to earth. Credit to : Scott Manley