The Hubble Space Telescope launches into orbit with Space Shuttle Discovery. Named after astronomer Edwin Hubble, who determined that the universe is expanding, HST is responsible for many major breakthroughs in astronomy.
HST's low earth orbit allowed it to be repaired, upgraded and serviced periodically by NASA. Serviceability became an important feature in HST's early days when scientists discovered that HST's state of the art 7.9 foot mirror had a tiny flaw in it, rendering many types of images in different spectra of light out of focus. Discovery was able to modify several systems inside the telescope to correct the error and eliminate the fuzzy pictures.
Between 1990 and 1997, HST performed some observations for amateur astronomers. Several such amateur studies were great successes, but budget cuts put a stop to the observations.
HST's successor will be the James Webb Space Telescope. It's mirror will be 21 feet in diameter, much larger than HST, and will enable it to concentrate on the study of stars born very near the time of the Big Bang. JWST will not sit in low earth orbit and will not be serviceable; instead it will be stably positioned near the L2 Lagrange point beyond the moon. JWST is currently scheduled for a 2018 launch.