With the rest of the shuttle fleet grounded once again by safety fears, Discovery continued its mission today, delicately performing a back flip and docking with the International Space Station (ISS) at 12:18 BST.

While Nasa engineers continued to examine footage of the apparently minor damage sustained by the shuttle on lift-off, Eileen Collins, the shuttle commander, guided Discovery towards the space station this morning.

As the shuttle approached to within 1,520m (5000 ft) of the station, Commander Collins told the ISS Commander, Sergei Krikalev: "We’re looking forward to seeing you guys. Your space station looks absolutely beautiful from the outside."

Commander Collins then steered the shuttle into a planned but unprecedented back flip to allow the two crew of the space station to examine the sensitive exterior of the spacecraft, which suffered minor "dings" when it took off from Cape Canaveral in Florida on Tuesday.

The shuttle hung upside down 182m (600ft) away from the station as the ISS crewmembers used powerful cameras to take photographs of the fragile tiles that protect the belly of the shuttle. The photographs, which were taken continuously for 93 seconds, were beamed back to Earth for analysis by Nasa.

Discovery then successfully docked with the ISS and the seven Nasa astronauts were welcomed through the airlock with hugs and traditional Russian gifts of bread and salt. The shuttle will now unload 15 tonnes of food and supplies into the station as the two spacecraft entwine for eight days orbits around Earth.

The crew of Discovery will install a new gyroscope and storage platform on the $95 billion (£54.5 billion) station, whose development has been slowed by the extended delays to the shuttle programme.

Today's success offered a bright contrast with the gloomy news conference held at Nasa yesterday, during which the managers of the shuttle programme announced that the the rest of the shuttle fleet, including Atlantis, which was on standby to rescue the crew of Discovery in an emergency, was grounded because of ongoing safety fears.

The launch of Discovery, during which several pieces of the spacecraft fell off but did not cause any serious damage, has been sufficient for Nasa to admit that two-and-a-half years and $1 billion (£573 million) of safety improvements have not been enough solve the problems which led to the Columbia disaster in 2003.

"You have to admit when you’re wrong. We were wrong," said Bill Parsons, manager of the shuttle programme, of the agency's confidence in its safety improvements.

"Until we’re ready, we won’t go fly again... I don’t know when that might be, so I’ll just state that right up front. We’re just in the beginning of this process of understanding," he added.

Nasa insists that Discovery is safe to continue its mission and return to Earth on August 7. As the shuttle docked with the ISS today, Michael Griffin, the Nasa Administrator told ABC television: "Everything that we see at this point says that the orbiter is in fact a clean bird."

Two significant pieces of debris fell from Discovery as it blasted off two days ago: an 4cm (1.5in) piece of protective tile from next to the nose landing gear and a larger chunk of foam from the shuttle's external fuel tank.

By chance, neither piece struck the spacecraft, as the suitcase-sized piece of foam did when it damaged the wing of Columbia in January 2003 15 days before it broke up 200,000ft above Texas as it re-entered the Earth's atmosphere.

Wayne Hale, the deputy shuttle program director, acknowledged that the piece of foam from the external fuel tank, which peeled off the shuttle two minutes after lift-off, could have caused mortal damage to Discovery: "We think that would have been really bad, so it’s not acceptable," he said.

The grounding of the shuttle fleet, the workhorses of Nasa's space programme, has cast unwelcome uncertainty over the most ambitious plans for the agency. Last year, President Bush announced plans to return astronauts to the Moon by 2020 and for a manned mission to Mars.

The current shuttle fleet is due to retire in 2010, when the orbiters will be replaced by a new shuttle. Sherwood Boehlert, Chairman of the House of Representatives Science Committee praised Nasa yesterday for handling the current situation "exactly right" but admitted that the ongoing difficulties had raised questions over the invigoration of the space programme.

"It doesn’t appear that the mission is in jeopardy. Nothing is in jeopardy except the schedule. But I don’t want to underestimate the seriousness of it in terms of the future," said Mr Boehlert.

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