For those who don't know what this is, the Manned Orbiting Laboratory was a plan in the 1960s to create a manned space station with a large telescope in it, for the purpose of reconnaissance. Essentially, a manned spy satellite.

The reason for this was that, at the time, spy satellites would take pictures on film, which would then be landed in capsules and interpreted - hence, there would be a significant delay between when a photo was taken, and when it could be used. The idea would be that the astronauts would be able to take pictures and interpret film on-orbit, and relay back the results.

As the ability to scan film in orbit was developed, and eventually electronic devices like CCDs, the MOL was cancelled before it became operation. Several of the MOL Astronauts transferred over to NASA, and eventually flew on the Space Shuttle.