The Hubble Space Telescope (HST) is the first optical telescope orbiting the Earth. The Hubble Space Telescope was named after American astronomer Edwin P. Hubble (1889-1953).

HST is a large space based observatory. It is a Low Earth Orbiting satellite. It is located about 375 miles above the surface of the Earth. Hubble completes an orbit around the Earth every 97 minutes. It has provided deep and clear views of the Universe.

HST was launched on April 24,1990. Its length is 13.2 meters and the maximum diameter is 4.2 meters . It weighs about 24000 lbs on Earth. It is about the size of a large school bus. It was designed to fit in the bay of the Space Shuttle, so that it could be easily deployed into the orbit. It is high enough so that it can escape the light distorting effects of Earth's atmosphere, but low enough so that can reach it easily enough during servicing missions. Hubble runs on batteries which are designed with a 15-year life. Tests performed recently by NASA engineers suggest that Hubble's batteries should last till 2009 before they reach a point where science can no longer be performed.

Initially Hubble costed $1.5 billion to build and put into orbit. Hubble's total budget in one year is in the range $230-250 million. The concept of servicing Hubble to upgrade its instruments rather than launching a whole new telescope has saved billions of dollars.

It views star material some 10 to 12 billion light years from earth, and its digital images have contributed greatly to our knowledge of astronomy and science. Hubble was designed to receive periodic visits from space shuttle astronauts who would perform routine maintenance and instrument upgrades. The last such service visit took place in 2002, and with NASA authorization on hold for a fourth and final service, the projected lifespan of Hubble's work is 2010.

HST is fulfilling the hopes astronomers have held from it. It is orbiting above the Earth’s distorting atmosphere and providing uniquely clear and deep views of the cosmos.

• The most detailed look at the farthest known galaxies in the Universe has been obtained by imaging from the Hubble Space Telescope.
• Hubble has detected several atomic constituents in the atmosphere of a planet outside our solar system.
• Hubble have discovered that dark energy is not a new constituent of space, but rather has been present for most of the universe's history. Dark energy is a mysterious repulsive force that causes the universe to expand at an increasing rate.
• Hubble Space Telescope captured the dramatic effects of the collision early July 4, 2005 between an 820-pound projectile released by the Deep Impact spacecraft and comet 9P/Tempel 1.
• Hubble was the first optical telescope to provide convincing proof of a black hole several billion times the mass of the sun in the early 90's.
• Hubble found evidence that black holes are at the core of most galaxies.
• Hubble found the origin of gamma rays which was the result of the most powerful cosmic explosion in distant galaxies in the early universe.
• Hubble viewed the birth of the stars. It revealed the divers and complex processes that influenced star formation.
• Hubble revealed the internal structures of the planet-forming dust disks.
• Hubble suggested the presence of newly formed planets.
• In1995, Hubble released one of its most famous images, the Eagle Eye Nebula which showed the emergence of stars from pillars of interstellar clouds.
• The telescope's images of dying stars help scientists understand the death process and how it is influenced by each star's specific circumstances.
• Hubble revealed views of the northern and southern lights on Jupiter, Saturn and Ganymede.
• In 1994 Hubble provided views of Comet Shoemaker-Levy 9's collision with Jupiter.
• Hubble has taken images of Jupiter's Great Red Spot.
• Hubble has taken the first detailed images of Pluto and its satellite Charon.
• Hubble has given new understanding of the atmospheres of Uranus and Neptune.
• Hubble has obtained the sharpest view of Mars from the Earth. Frosty white water ice clouds and swirling orange dust storms above a vivid rusty landscape reveal Mars as a dynamic planet.
• Hubble's Ultra Deep Field is the deepest astronomical optical image ever taken. The findings were released in March of 2004.Scientist were surprised to find assortment of at least 10,000 galaxies at various stages of evolution.