Spitzer was the only one of the Great Observatories not launched by the Space Shuttle. It was originally intended to be so launched, but after the "Challenger" disaster, the Centaur LH2/LOX upper stage that would have been required to push it into a heliocentric orbit was banned from Shuttle use. Titan and Atlas launch vehicles were canceled for cost reasons. After redesign and lightening, it was launched by a Delta II launch vehicle instead. It was called the Space Infrared Telescope Facility (SIRTF) before launch.