Marshall Space Flight Center previous Spacelab missions were operated. The advent of the Space Shuttle made possible several major space programs in which MSFC had significant responsibilities. These were the International Space Station, the Hubble Space Telescope, the Chandra X-Ray Observatory, and the Compton Gamma-Ray Observatory. The latter three are part of NASA's series of Great Observatories; this series also includes the Spitzer Space Telescope, but this was not launched by a Space Shuttle and MSFC had no significant role in its development. A manned space station had long been in the plans of visionaries. Wernhar von Braun, in his widely read "Collier's Magazine"
Space Shuttle program from the back of a specially modified Boeing 747, only for initial atmospheric landing tests (ALT). "Enterprise"'s first test flight was on February 18, 1977, only five years after the Shuttle program was formally initiated; leading to the launch of the first space-worthy shuttle "Columbia" on April 12, 1981 on STS-1. The Space Shuttle program finished with its last mission, STS-135 flown by "Atlantis", in July 2011, retiring the final Shuttle in the fleet. The Space Shuttle program formally ended on August 31, 2011. Before the Apollo 11 moon landing in 1969, NASA began early studies of space shuttle designs.