The US space agency Nasa is drawing up plans to launch a $1bn (£547m) rescue mission for the ailing Hubble space telescope, considered by many to be the most important telescope ever built.
In what amounts to a U-turn, Sean O'Keefe, who heads the agency, has instructed engineers at Goddard Space Flight Centre in Maryland to prepare a mission to fix the orbiting telescope in time for a 2007 launch.
The move represents a sudden change of heart by Nasa. Shaken by last year's loss of the shuttle Columbia and its seven crew, Nasa recently scrubbed a long-planned shuttle mission to the telescope on the grounds that it was too risky.
Hubble is badly in need of replacement batteries and new gyroscopes. Rather than fix it, Nasa had been considering plans to de-orbit the telescope and ditch it in the sea.
Now engineers hope to send a Canadian robot called Dextre to carry out the repairs.
"Everybody says: 'We want to save the Hubble' - well, let's go save the Hubble," Mr O'Keefe said. "Rather than just sitting there and talking about how we think we're going to do it, we've got an option we're ready to go with."
Dextre - the informal name for the Canadian Space Agency's special purpose dextrous manipulator - is a gangly looking machine with two three-metre arms that pivot around a robotic torso. Nasa engineers have nine months to test Dextre and find out if it is capable of carrying out the complex tasks required to service Hubble. Only then will Nasa decide whether to commit to a mission expected to cost between $1bn and $1.6bn.
If the mission is successful, it could extend Hubble's expected life by five years, taking it beyond the planned launch date for its successor, the James Webb telescope in 2011.
Hubble has revolutionised astronomers' view of the universe. This year, the telescope captured beautiful images of a star in its death-throes and delivered the best-ever snapshot of the early universe, revealing 10,000 fledgling galaxies. The telescope is credited with discovering up to 100 new planets orbiting stars outside our solar system.
"Hubble is without a hint of exaggeration the biggest success Nasa has had since they put Neil Armstrong on the moon. Scientifically, it's ... right up there with Galileo's telescope in terms of the impact it has had," said Gerry Gilmore, deputy director of the Institute of Astronomy at Cambridge University.
Privately, scientists raise doubts over whether a robot can perform the repairs.
"If the robot mission succeeds in repairing Hubble, it'll be a triumph. But if they try and fail, they've got a good case for sending up astronauts," said Professor Gilmore.
Ultimately, Nasa will have to send some kind of mission to Hubble. Even if plans to repair it are scrapped, engineers must eventually work out how to bring the bus-sized telescope safely back to Earth.
