Hubble: Why the world-famous telescope will go out in a blaze of glory

When it blasted off 20 years ago, few thought it would succeed. But it showed us a universe we didn't know existed, says Nick Harding

In years from now, when the fiery carcass of the Hubble Space Telescope streaks across the sky and falls to Earth as lumps of molten metal, there won't be a dry telescope eyepiece on the planet. The passing will be marked by astronomers with the kind of eulogies usually reserved for noteworthy humans, not bus-length space-based visual apparatus.

In the 20 years it has been orbiting the globe, Hubble has become world-famous. It has helped to redefine the parameters of the Universe, revolutionised astronomy, and shown us glimpses into the very nature of cosmic creation. Not bad at all considering that, at one point, Hubble was a technological calamity, destined to be one of the most expensive white elephants in scientific history.

Perhaps that is why Hubble has garnered such popular appeal. It is not just a machine. Its operational life is interwoven with triumph-over-adversity narratives that grab the imagination. It's an orbiting mechanised Rocky Balboa.

As author of the stunning new book Hubble: Window on the Universe, Giles Sparrow explains: "Part of the reason it has such popular appeal is the Cinderella story. Hubble is the little telescope that could."

When it was first launched into orbit 353 miles above the planet by space shuttle Discovery in 1990, Hubble was the little telescope that couldn't. After decades in development, an initial funding input from Nasa of $36m and a launch delayed for years because of the Challenger shuttle disaster of 1986, when Hubble eventually started working it soon became apparent that it was faulty.

"It was short-sighted," Sparrow says of the affair.

The 2.5m mirror mounted on the telescope that collects light from distant corners of the Universe to process into pictures was out of shape by one-fiftieth of a human hair and the initial images it sent back to Earth were blurred. It took another three years before the fault was rectified in one of the most complex space missions ever attempted (Hubble travels at five miles a second and takes just 97 minutes to circle the planet). By that time, Hubble had become a laughing stock. When it was fixed, however, the advantages of siting a telescope away from the distorting effects of the Earth's atmosphere soon became apparent and the images that able-sighted Hubble began to capture were astounding.

The concept of a space telescope was first theorised in 1923 and the foundations for the Hubble project were laid by US physicist Lyman Spitzer in 1946 when he outlined the advantages of developing an extraterrestrial observatory. Because the Earth's atmosphere distorts light from space – which is why stars appear to twinkle when viewed from the ground – and also blocks some wavelengths of light partially or entirely, Earthbound observatories never truly monitor clearly. Throughout the 1960s and 1970s, Spitzer was an enthusiastic lobbyist for the Hubble project and remained involved in the programme until his death in 1997.

The Hubble telescope itself was named after astronomer Dr Edwin Hubble, who, in 1929, discovered the notion of an expanding universe which formed the basis of the Big Bang theory. The Hubble telescope's "Key Project" was to further Dr Hubble's discovery and measure the rate of this expansion, thereby enabling scientists to put an accurate age on the date of the Big Bang and the Universe. It took almost eight years of observations to complete this objective, but thanks to the telescope we now know that the Universe is expanding at a rate of 70 kilometres per second per megaparsec (a unit of astronomical distance equivalent to 3.26 million light years) and that space began to expand from a single point around 13.7 billion years ago. Previously, the figure had been vaguely put at somewhere between 10 and 20 billion years ago.

Sparrow says: "Establishing accurately the rate of universal expansion for the first time is what Hubble will be remembered for 1,000 years from now."

Hubble's scientific importance has been huge. It has also played a key role in the discovery of dark energy, a force that causes the expansion of the Universe to accelerate, and has photographed galaxies in all stages of evolution, helping scientists to understand how they form. It has discovered stellar nurseries – birthing grounds for new planets – and made the first visual observation of an extrasolar planet orbiting a star 25 light years away, uncovering details about its composition and atmosphere. It has discovered the earliest galaxy, looking back into the universal history at light emitted by stars formed just 300 million years after the Big Bang. Within our Solar System it has captured images of a comet colliding with Jupiter and has also observed a rare asteroid collision.

Hubble's control centre is based at the Space Telescope Science Institute in Baltimore, and although the project is Nasa-funded with help from the European Space Agency, it is used by the global science community. More than 4,000 astronomers have used Hubble, and all the data it collects is publicly available online.

"It was the first observatory of the internet age. All its raw data is available, as is the software for processing images from that data," Sparrow says. "There are people who have put together some fantastic new images using what is available. It is the people's telescope."

The images Hubble has produced have captured the public imagination but while it has been in space, technological advances on the ground mean that a new generation of observatories can now produce images as sharp as Hubble's and see farther back in time.

Hubble's days are numbered and last year, shuttle astronauts performed the final service mission on the telescope. It will now continue its observations until it is decommissioned, probably around 2014. A new infrared space telescope, the James Webb Space Telescope, is due for launch in the same year. However, because of the technology that uses, it will not deliver show-stopping visuals like Hubble has.

As Sparrow explains: "Because James Webb is infrared, the images it will produce will not have the same resonance. They will be scientifically interesting but will not deliver that visual 'wow factor' that Hubble does. That is why people relate to Hubble so much. It is like a giant eye. It is focused on real light, like our eyes [are]. It has done a fantastic job enthusing the public; its images have been seen by billions of people."

One of the last adjustments made on the Hubble telescope was to fit it with a docking point which will be used by an unmanned craft to drag it into a controlled fall back to Earth when its declining orbit reaches a certain point. It will burn up on re-entry. Despite calls to have it brought back to Earth as a museum piece, Nasa's decision to shelve the shuttle fleet means that there will be no means to salvage Hubble when it eventually reaches the end of its operational life. It may have started life as an object of ridicule but Hubble will go out in a blaze of glory.

'Hubble: Window on the Universe' is published by Quercus (£20). To order a copy for the special price of £18 (free P&P), call Independent Books Direct on 08430 600 030, or visit www.independentbooksdirect.co.uk.