Marshall Space Flight Center of the launch vehicle. Finally, on April 24, 1990, on Mission STS-31, Shuttle "Discovery" launched the Hubble telescope successfully into its planned orbit. Almost immediately it was realized that the optical performance was not as expected; analysis of the flawed images showed that the primary mirror had been ground to the wrong shape, resulting in spherical aberration. Fortunately, the Hubble telescope had been designed to allow in-space maintenance, and in December 1993, mission STS-61 carried astronauts to the Hubble to make corrections and change some components. A second repair mission, STS-82, was made in February 1997, and a third, STS-103,
Spitzer Space Telescope into a more extended mode of operation, possibly in association with a future space platform or space station. SIRTF would be a 1-meter class, cryogenically cooled, multi-user facility consisting of a telescope and associated focal plane instruments. It would be launched on the Space Shuttle and remain attached to the Shuttle as a Spacelab payload during astronomical observations, after which it would be returned to Earth for refurbishment prior to re-flight. The first flight was expected to occur about 1990, with the succeeding flights anticipated beginning approximately one year later. However, the Spacelab-2 flight aboard STS-51-F showed that the Shuttle