Watch video of second spacewalk

Astronauts have assembled a massive robot handyman called Dextre that will carry out much of the maintenance work at the International Space Station.

Richard Linnehan and Robert Behnken succeeded in putting together the gangly humanoid robot with 11ft arms during a seven-hour spacewalk that finished earlier today - by chance, the 43rd anniversary of the first spacewalk.

Later, after they have slept, the astronauts will move Dextre by remote control to its new home on the side of an American space laboratory called Destiny.

Nasa says that the robot will free the astronauts to spend more time on scientific experiments rather than arduous and potentially dangerous spacewalks to carry out repairs.

Mission Control praised Linnehan and Behnken for their work, though they hit a snag when a suitcase-sized science experiment refused to hook itself on to the side of Columbus, the newly arrived European space laboratory.

Zebulon Scoville, the lead spacewalk officer for the Endeavour shuttle mission to the International Space Station (ISS), said the pair were heroic. "You're making rock stars question their job choice," he said.

Dana Weigel, the lead ISS flight director, said: "They did a fantastic job. Some of the manoeuvres they had to do were like threading a needle."

Linnehan consoled his colleague over the recalcitrant experiment. "You gave it your all, Bob. No one could have done more," he said.

Endeavour carried Dextre out to the space station in pieces. The $200 million robot has cameras for eyes, a large tool kit and a spare parts platform.

The shuttle crew are to make a record five spacewalks - today's was the third - during their 16-day visit to the ISS. Their next tasks include preparing for the arrival of a Japanese space laboratory called Kibo (hope) in May, and practising heat shield repairs for a future mission to the Hubble space telescope.

Nasa has ten more shuttle flights planned to complete the $100 billion space station and deliver supplies before the shuttles are retired in 2010.

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