Hubble Space Telescope in orbit. Artist's impression of the Hubble Space Telescope (HST) in its observation mode in orbit. The protective door at the top end of the telescope is shown open. The HST was launched on 24 April 1990 by the Space Shuttle. Soon after, it was discovered that a manufacturing error had left the main mirror with an optical aberration which degrades the image. A computer method has been used to try to correct for this, and an optical 'fix' is due to be made during a servicing mission in late 1993. It is hoped that the HST will then achieve its full potential, although it has already made many important discoveries and observations.