Hubble Space Telescope

Dr Duncan L Copp

Updated June 2003

Italy, 1610, and a scientific revolution was about to take place. On one clear evening, Galileo Galilei turned a telescope towards the heavens for the first time. On that night, and others that followed, he observed celestial sights that revolutionised our perception of the Universe forever. Today we are in the midst of another astronomical revolution. The Hubble Space Telescope, a similar yet vastly superior instrument, is providing an enlightening new window on the Universe.

Modern telescopes are synonymous with modern astronomy. They encompass state-of-the-art computer technology and optics, allowing the observation of far-flung corners of the Universe. Yet no matter how sophisticated these telescopes are there is an inescapable problem when observing from the surface of the Earth – it has a cloaking atmosphere.

The Earth's atmosphere is the bane of astronomers, as it creates a multitude of frustrating problems:

• Observations are made difficult by cloud, mist and fog.
• Air pollution causes irritating sky glow.
• Air currents ensure the atmosphere is in constant turmoil, even on the clearest night.
• Molecules such as water absorb important light wavelengths (eg infrared and ultraviolet) that hold valuable information on a plethora of astronomical objects.

All in all, the atmosphere makes observation from the Earth's surface like staring up from the bottom of a murky rippling pond. The only solution is to rise above it all, literally.

The idea of a telescope in space is not particularly new. The great German space flight pioneer, Hermann Oberth, first proposed it in the 1920s. But the Hubble story really began when American astronomer, Lyman Spitzer, began a lobbying campaign in 1946. However the path to place a telescope in orbit would be long and hard.

Hubble Hubble, toil and trouble

In 1972, 26 years after Spitzer's first proposal, Nasa began to draw up plans for a space telescope. The telescope would have a large mirror, 3 metres in diameter, and would be placed and retrieved from orbit using the space shuttle, which was then under development. Launch was set for 1980.

Almost instantly, the project ran into financial problems. As the 1974 oil crisis hit hard, Congress had little interest in spending money on an orbiting telescope and funding, like the oil, ran dry. After more lobbying, still mainly from Spitzer, funding began again in 1977. In the interim, Nasa had sought financial help from Esa (European Space Agency). And although the project was back on, the telescope had been shrunk, to a smaller mirror diameter of 2.4 metres.

During the next five years, the Hubble Space Telescope (HST) took shape. But as with most technologically ambitious projects the cost was underestimated, as was its complexity. The launch repeatedly slipped and the budget ballooned. During the early 1980s, the only thing in focus was Hubble's cost and technical problems. Astronomical observations seemed a long way away.

But as the second shuttle mission of 1986 thundered skyward, the launch of HST was just months away. However, the unthinkable was about to happen – space shuttle Challenger was never to reach orbit. It exploded shortly after lift-off, killing her crew of seven astronauts. The shuttle fleet was grounded and HST was stranded. Would the world's premier telescope ever make it into space?

Four years later, on 24 April 1990, space shuttle Discovery successfully lofted HST into orbit, 600 kilometres high. The wait was finally over – let the observing begin!

The first results from the Hubble Space Telescope were perhaps the most eagerly awaited in the history of science. After a few months of initial optical calibrations the first images were beamed back to Earth. The scientists were speechless, but for all the wrong reasons. The images were out of focus. Frantic checks confirmed the unthinkable; the telescope's primary mirror had been manufactured incorrectly. The technical term was 'spherical aberration' – the bare fact was that Hubble's vision was blurred.

There was only one viable solution – Hubble would need glasses. In December 1993, astronauts Story Musgrave and Jeff Hoffman, aboard space shuttle Discovery, rendezvoused with the partially-sighted telescope. And in what has been described as the most rehearsed space mission ever, the men spent 35 hours space-walking, as they installed a series of correcting lenses.

Hubble had been able to conduct some worthwhile science during its short-sighted years, with the help of computer programmes that counteracted its spherical aberration. However with correcting lenses installed, Hubble regained most of its sight.

Astronomical results

Although achieving the vision of HST was arduous, the scientific payoff during 12 years of operation has been beyond the wildest dreams of most astronomers. Observing in a multitude of wavelengths (visible light, infrared, ultraviolet), HST's achievements are unsurpassed, ushering in a new astronomical revolution.

One astronomical conundrum that Hubble has shed light upon is that first raised by the man in whose posthumous honour the telescope was named, Edwin Hubble. In 1929, the American astronomer discovered that the Universe was expanding. The profundity of the discovery was that the Universe must have had a beginning – so how old is it now? The answer depends on the rate of its expansion, a rate known as the Hubble Constant. The faster the expansion, the younger the Universe. By observing previously unseen stars in distance galaxies (called Cepheid variables) HST has refined the measurement of expansion, aging the Universe at around 14 billion years.

Closer to home, HST is helping piece together the first stages of star and planetary formation in our galaxy. With its unrivalled seeing power, Hubble has peered into the heart of star nurseries such as the Orion Nebula. Here it has discovered embryonic stars surrounded by dark cool disks of matter known as proto-planetary disks. These new observations support the theory that our solar system formed from a large condensing molecular cloud around 4500 million years ago.

Within our solar system itself, Hubble has provided near continuous observation of the planets in detail only bettered by visiting spacecraft. Planetary scientists have been able to track the evolution of global dust storms on Mars and observe the intricate workings of Saturn's rings. In 1994, they witnessed the powerful cosmic collision of comet Shoemaker-Levy-9 with Jupiter – a sobering reminder that our solar system is far from static.

But perhaps the most memorable images to come from Hubble are the 'deep field frames'. In 1995 and 1998 a team of astronomers focused the telescope on two tiny areas of the sky, each the size of a grain of sand held at arms length. After capturing an image over 10 days, Hubble revealed that each tiny patch of sky contained thousands of faint galaxies, each containing billions of stars. These humbling images show the true immensity of our Universe – a fitting achievement for the Hubble Space Telescope and those who dedicated their working careers to ensure its success.

On in the new century

March 2002 saw the fourth successful Hubble servicing mission. During a 12-day mission, astronauts aboard space shuttle Columbia performed five space walks and installed the Advanced Camera for Surveys, or ACS. Composed of three separate cameras, the ACS can observe the Universe in wavelengths ranging from visible to far ultraviolet. It produces extremely detailed pictures of the inner regions of galaxies. It surveys the distribution of galaxies, helping astronomers map the fabric of the Universe. It can search neighbouring stars for orbiting planets and planets in the throes of forming. And it studies weather on planets in our own solar system.

The loss of space shuttle Columbia on 1 February 2003 and the subsequent grounding of the shuttle fleet are likely to have only a minimal effect on the operation of HST, as long as no major problems arise with the telescope requiring an emergency repair mission. Before the loss of Columbia, the next trip out to Hubble was planned for February 2005, when the new WFC-3, a sensitive and efficient wide field camera, would be installed. The exact timing of the mission is now under review.

The telescope continues to work, around the clock, and will hopefully bring us more wondrous insights into the Universe before its career review, currently planned for 2010.

You may also be interested in these other Channel 4 articles

International Space Station
Is the International Space Station set to change the course of human history, or is it too costly with too little scientific return?

Mir Space Station
History of the stage on which some of the most notable and dramatic episodes in space were played out.

Find out more

Channel 4 is not responsible for the content of third party sites

Websites

The Hubble Project
http://hubble.Nasa.gov
Nasa's Hubble Project site. Provides an overview of the Hubble's accomplishments, its technology and maintenance of the telescope. Check out the live webcam footage.

The Hubble Site
http://hubble.stsci.edu/
A collection of interactive, educational resources and spectacular Hubble images. Explore the Universe while learning the principles of maths and science.

Space Telescope Science Institute
http://oposite.stsci.edu/pubinfo/Pictures.html
Pictures from the Hubble telescope.

Association of Universities for Research in Astronomy
www.seds.org/hst/hst.html
More pictures taken by the telescope.

Space
www.space.com
The definitive space website which offers compelling content, featuring news, information, technology, science, business, entertainment and an education channel.

Destination Mars
www.channel4.com/science/microsites/M/mars/
Channel 4 site that tells the story of Mars exploration and shows how scientists are creating their own versions of Mars on Earth, so they can prepare the planet's first explorers. Check out the space game.

Books

Hubble Vision: Further adventures with the Hubble Space Telescope by Carolyn Collins Petersen and John C Brandt (Cambridge University Press, 1995) US edition only, available through online bookshops.
Illustrated book which provides a portfolio of the latest images from Hubble, with a text explaining its discoveries. It's also an introduction to astronomy and gives laypeople an idea of what astronomers do.

Collins Gem Space Exploration (HarperCollins, 2001) £4.99
Looks at the exploration of space, the stars, walking on the moon and beyond. Quick and easy reference book.

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