Despite the public's memory of its faulty mirror, it is clear that the Hubble Space Telescope (HST) has had a profound impact on astronomy.

Our progress in understanding the Universe has been driven by technology. Hubble, with its powerful vision, has shown us stunning new sights and brought us closer to the big questions of existence.

Hubble history

1977 - Project begins 1985 - Hubble built 1990, 24 April - Hubble launched 1990, 18 May - First light 1993, December - Flaw repaired 2000, 24 April - 10 years of Hubble 2010 - End of Hubble mission

A century ago, astronomers in the United States started building giant reflecting telescopes, unprecedented in their size and vision. One of these, the 100 inch Mount Wilson reflector, was to make one of the greatest scientific discoveries ever.

It was made by astronomer Edwin Hubble. He looked at distant galaxies with the reflector and discovered that the Universe was expanding. The effect was named after him - Hubble's law.

Big bang

It meant that the Universe had an origin in a cataclysmic explosion we now call the Big Bang. But the big question was how old is the cosmos? Answering that question accurately required a new telescope.

Larger telescopes were built, such as the mighty Mount Palomar 200-inch reflector, but it soon became clear that something rather different was required.

The need was for a new telescope that did not have to peer through the murky and turbulent atmosphere; a new telescope that had a clear view of space. In other words, a telescope actually in space.

Astronomers have always wanted a space telescope and it is surprising that it took them so long to get one into orbit.

Rocket science

In the 1920's, rocketry pioneer Hermann Oberth wrote about a telescope in orbit around the Earth. Throughout the 50s and 60s reports and preliminary designs were circulated, but nothing got off the drawing board.

But in the 70s the project got underway. It seemed that almost every astronomer, be they involved in the project or not, started talking about the promise of the space telescope.

The telescope was put into orbit by a Nasa space shuttle

It was originally designed to be much larger, but in the end it had a 240-cm (96-inch) mirror - not very big by telescopic standards. But being in orbit made all the difference.

It was called the Hubble Space Telescope, to honour the famous astronomer. It would be able to see many times further than any other telescope and would accurately measure the size of space.

But as the final preparations were made for Hubble's launch, the 1986 Challenger disaster grounded the Space Shuttle fleet and Hubble had to wait.

And little did the scientists know that as it sat on the ground, in the world's biggest clean room, it held at its heart an almost fatal flaw.

Words by Dr David Whitehouse; Images courtesy of the Space Telescope Science Institute