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
Spitzer Space Telescope environment was poorly suited to an onboard infrared telescope due to contamination from the relatively "dirty" vacuum associated with the orbiters. By September 1983 NASA was considering the "possibility of a long duration [free-flyer] SIRTF mission". "Spitzer" is the only one of the Great Observatories not launched by the Space Shuttle, as was originally intended. However, after the 1986 Challenger disaster, the Centaur LH2–LOX upper stage, which would have been required to place it in its final orbit, was banned from Shuttle use. The mission underwent a series of redesigns during the 1990s, primarily due to budget considerations. This resulted