A FORMER Top Gun stunt pilot is to lead a shuttle mission 320 miles above Earth to rescue the Hubble Space Telescope, one of the greatest scientific instruments ever created.

Reversing a previous ruling that such a voyage would be too dangerous and costly, Michael Griffin, the head of Nasa, has announced that seven astronauts would be sent to repair the $1.5 billion (£800 million) telescope, which has been responsible for solving some of the greatest mysteries of the cosmos.

“While there is an inherent risk in all spaceflight activities, the desire to preserve a truly international asset like the Hubble Space Telescope makes doing this mission the right course of action,” he said.

Without new batteries and an instrument upgrade, the 16- year-old deep-space observatory will go into meltdown within two to three years, depriving scientists and spacewatchers of what they consider to be the finest eye in the sky since Galileo perfected the invention of the telescope 400 years ago.

Using a system of high-powered mirrors and cameras, the Hubble — named after Edwin Hubble, the so-called father of observational cosmology — is able to peer back billions of years into space and was the first to measure the size and age of the Universe precisely. It has brought spectacular images of distant galaxies and planetary gas clouds, and found evidence of dark energy, the mysterious force behind the ongoing expansion of the Universe.

In 1999 it captured images of the blast from a gamma ray, the most powerful explosion ever recorded, and provided unprecedented views of the fireballs and gas clouds created on Jupiter after it was struck by the Shoemaker-Levy 9 comet the following year.

“It’s gone to places in the universe that we never knew existed,” said Barbara Mikulski, a Democratic senator for Maryland, who has long pushed for the telescope to be saved. “It belongs to every child who wants to know, ‘What’s the Universe beyond my village, beyond my town?’ ” She added yesterday : “It’s a great day for science, it’s a great day for discovery, it’s a great day for inspiration.”

The commander of Mission STS-125 from Kennedy Space Centre at Cape Canaveral, Florida, between the spring and autumn of 2008, will be Scott “Scooter” Altman, 47, who joined Nasa’s astronaut corps in 1995 after a career flying F14 fighter jets with the US Navy, where assignments included leading strike raids over southern Iraq and performing Tom Cruise’s aerial stunts in the 1986 film Top Gun.

Nasa must fly 14 more missions to the International Space Station 220 miles above Earth before retiring the ageing space shuttle fleet in 2010. Fixing Hubble will require the astronauts to perform five back-to-back spacewalks, during which they will either grapple their way over the telescope’s 12-ton frame or stand on the end of the shuttle Discovery’s robotic arm to reach the relevant areas for repair

They will fit new instruments and cameras and replace one of the telescope’s three broken gyroscopes, which control its position in orbit. An attempt will also be made to replace the Space Telescope Imaging Spectrograph, which stopped working in 2004 but which is important to Hubble’s ability to take high-resolution images of stars and distant galaxies in visible and ultraviolet light. One false move could puncture their pressurised spacesuits or irreparably damage the 12-ton Hubble’s complex and fragile equipment.

George Whitesides, the executive director of the National Space Society, said: “Hubble is Nasa’s astronomical crown jewel and the decision to extend its life is the right choice. Fixing Hubble is a risk worth taking — and courageous astronauts stand ready to do the job.”

EYE ON THE SKY

• Astronomer Lyman Spitzer came up with the idea of a space-based telescope in 1946. He realised that without the distorting effects of the atmosphere, images would be far clearer
  
  
• Congress approved funding for Hubble in 1978. The project went over budget and missed deadlines, with the launch date pushed further back by the Challenger disaster
  
  
• Within weeks of the 1990 launch, it was realised that the telescope’s mirror was flawed. Images were only marginally better than those obtained on the ground
  
  
• The flaw was corrected in 1993. Since 1993 Hubble has been arguably the most useful astronomical tool in history.
  
  
  
  
• It is named after astronomer Edwin Hubble, who discovered that the universe was expanding

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