Hubble Space Telescope data, while the Goddard Space Flight Center controls the spacecraft. Space telescopes were proposed as early as 1923. Hubble was funded in the 1970s, with a proposed launch in 1983, but the project was beset by technical delays, budget problems, and the "Challenger" disaster (1986). When finally launched in 1990, Hubble's main mirror was found to have spherical aberration, compromising the telescope's capabilities. The optics were corrected to their intended quality by a servicing mission in 1993. Hubble is the only telescope designed to be serviced in space by astronauts. After launch by in 1990, five subsequent Space Shuttle missions
Space Shuttle program launched on September 29, 1988. The longest Shuttle mission was STS-80 lasting 17 days, 15 hours. The final flight of the Space Shuttle program was STS-135 on July 8, 2011. Since the Shuttle's retirement in 2011, many of its original duties are performed by an assortment of government and private vessels. The European ATV Automated Transfer Vehicle supplied the ISS between 2008 and 2015. Classified military missions are being flown by the US Air Force's unmanned space plane, the X-37B. By 2012, cargo to the International Space Station was already being delivered commercially under NASA's Commercial Resupply Services by SpaceX's