'Son of Hubble'
In 2008 - astronomers hope - Hubble will be succeeded by a bigger and better instrument,
currently
known as the Next Generation Space Telescope. It will also be cheaper: NASA is well aware that Hubble ran well over budget, costing almost $2 billion at launch. The Next Generation Space Telescope must come in at quarter of that amount.
Currently, four groups are tendering for the contract. All of them are designing a main mirror eight metres across - over three times bigger than Hubble's, which means it can see objects ten times fainter. It's impossible to put such a big mirror inside a rocket for launch, so it will be made in sections which will click together once the telescope is in space.
The new telescope will be much flimsier than Hubble, and so much lighter in weight. Instead of a space shuttle, it's need only a medium-class rocket launcher. And, instead of orbiting the Earth, the Next Generation Space Telescope will follow its own orbit around the Sun - 1.5 million km beyond Earth's orbit. At this location, the so-called Lagrangian-2 point, our planet's gravity still ensnares the telescope, so it travels with the Earth through space at a constant distance.
Huge solar panels provide the telescope with power, and - just as important - shield it from the Sun's heat. With the Next Generation Space Telescope naturally cooled down to the temperature of deep space, it can observe faint heat signals from the farthest reaches of the Universe. It will peer beyond where even Hubble can see, and explore an epoch before the youngest
galaxies explored by Hubble.
With this ultimate time machine, cosmologists hope to puzzle out the last remaining major mystery of the Cosmos - how did stars and galaxies first form. The Next Generation Space Telescope's infrared cameras will reveal the very first galaxies forming after the Big Bang. The early stars in these galaxies shone in ordinary light - like the Sun - but the expanding Universe has stretched this radiation so that it arrives here as infrared.
Just as Hubble was launched to measure the age of the Universe, yet became the ultimate exploring machine in all areas of astronomy, so the Next Generation Space Telescope will undoubtedly reveal far more than anyone can currently predict.
A stately retirement?
Currently, NASA intends to close Hubble down in 2010. But it hasn't decided what to do with the venerable instrument then. One option is to raise it to a higher orbit, where it will 'hibernate' indefinitely. Another is to bring Hubble back to Earth, for a place of honour in the Air and Space Museum in Washington.