U.S. Centennial of Flight Commission home page

Hubble Space Telescope


Deployment of HST after 2nd servicing mission
Hubble Space Telescope
Credits - NASA

The Hubble Space Telescope (HST), named after American astronomer Edwin P. Hubble, is the most sophisticated telescope ever orbited. It has contributed more to changing our understanding of the Universe than any other scientific instrument. HST is a joint project of the National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA) and operates for the benefit of scientists worldwide. Every day, Hubble archives 3 to 5 gigabytes of data and delivers between 10 and 15 gigabytes to astronomers all over the world. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, is responsible for conducting and coordinating the science operations of telescope.


The idea for such an observatory first surfaced in the 1940s; it was authorized by the U.S. Congress in 1977, and designed and built in the 1970s and 1980s. Launched on April 25, 1990, from the Space Shuttle Discovery, it orbits 375 miles (600 kilometers) above Earth.. Its science instruments include three cameras, two spectrographs, and fine guidance sensors. Its primary mirror has a diameter of 94.5 inches (240 centimeters). The telescope is able to produce high-resolution images of astronomical objects of great clarity, brightness, and detail because it is located above the Earth's atmosphere, which limits and distorts observations made by ground-based telescopes with comparable optics.


The telescope was designed for long-term use, made possible by regular servicing missions that repair or replace worn out or malfunctioning parts and upgrade equipment to the latest state of the art. It is the first scientific mission of any kind designed for routine servicing by spacewalking astronauts. Its modular design allows the astronauts to take it apart, replace worn out equipment, and upgrade instruments. Each time a science instrument in Hubble is replaced, it increases Hubble scientific power by a factor of 10 or greater.


Although it was discovered soon after launch that the primary mirror on the telescope had been manufactured with a spherical aberration, resulting in fuzzy images, the first servicing mission in December 1993 corrected the condition and it has returned top-quality images ever since. As of March 2002, there have been four visits to the telescope.