Space shuttle cleared for return

The Discovery space shuttle has been cleared for re-entry to Earth next week after Nasa officials gave its heat shield a clean bill of health.

Analysts at mission control in Houston had spent days looking at images for possible damage caused by Tuesday's lift-off from Cape Canaveral, Florida.

But they said several nicks and spots seen were no cause for alarm.

In 2003, space shuttle Columbia broke up on re-entry after lift-off debris pierced its heat shield.

Discovery is just the second shuttle flight since the disaster, in which all seven crew members died.

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Nasa engineers in Houston said it was not necessary to have an astronaut conduct a spacewalk to make minor repairs to the shield.

DISCOVERY SHUTTLE FLIGHT Mission known as STS-121 Discovery's 32nd flight 18th orbiter flight to ISS Lift-off: 1438 EDT, 4 July Location: Kennedy Space Center, Launch Pad 39B Objective: To test new safety equipment and procedures Payload: Cargo bay has 12.75t of equipment and supplies Crew: Lindsey, Kelly, Fossum, Nowak, Wilson, Sellers, Reiter

Discovery is currently docked with the International Space Station (ISS) orbiting the Earth.

Commander Steven Lindsey was told by mission control: "The thermal protection system is 100% clear for entry."

Lindsay replied: "That is great news. That's fantastic."

The shuttle is scheduled to return to the Kennedy Space Center on 17 July after one last check that it has not been hit by small meteorites.

Engineers had been checking a 5cm piece of fabric sticking out from thermal tiles but concluded it posed no concern for re-entry.

British-born astronaut Piers Sellers and colleague Mike Fossum finished their first spacewalk on Saturday, carrying out repairs to the exterior of the ISS.

Two more walks are planned for Monday and Wednesday.

Nasa has made a number of modifications to its orbiter fleet since damage on lift-off to Columbia led to it breaking up on re-entry.