"We in astronomy have an advantage in studying the universe, in that we actually see the past."
Lord Rees, Astronomer Royal for England
Often known simply as Hubble, the Hubble Space Telescope was named for Edwin Hubble, the U.S. astronomer who showed the existence of other galaxies outside the Milky Way. Hubble is an orbiting reflecting telescope designed to study the distant universe in visual light. Funded by the National Aeronautics and Space Administration (NASA) since 1977, its launch was planned for 1986, but the Challenger Space Shuttle tragedy put it back until April 1990.
The four instruments attached to the telescope focal plane were designed to be modular, and it was intended that they should be replaced by other instruments during the mission. This attribute was extremely useful because it was soon found that the main mirror had a design fault. A space shuttle rescue mission in 1993 corrected the problem.
Apart from capturing spectacular images of cosmic objects, Hubble can expose its detectors to the same region of sky for several days, and thus image objects that are much more distant from Earth. By searching for supernova explosions in distant galaxies, Hubble has discovered that the expansion of the universe is actually accelerating.
