Hubble Space Telescope be kept in a clean room, powered up and purged with nitrogen, until a launch could be rescheduled. This costly situation (about per month) pushed the overall costs of the project even higher. This delay did allow time for engineers to perform extensive tests, swap out a possibly failure-prone battery, and make other improvements. Furthermore, the ground software needed to control Hubble was not ready in 1986, and was barely ready by the 1990 launch. Eventually, following the resumption of shuttle flights in 1988, the launch of the telescope was scheduled for 1990. On April 24, 1990, successfully launched the
Space Shuttle Magnus (Mission Specialist 1), and Rex Walheim (Mission Specialist 2); they conducted the 135th and last space Shuttle mission on board "Atlantis", which launched on July 8, 2011, and landed safely at the Kennedy Space Center on July 21, 2011, at 5:57 AM EDT (09:57 UTC). NASA announced it would transfer orbiters to education institutions or museums at the conclusion of the Space Shuttle program. Each museum or institution is responsible for covering the cost of preparing and transporting each vehicle for display. Twenty museums from across the country submitted proposals for receiving one of the retired orbiters. NASA also