Space shuttle ready to head home

The shuttle took new solar panels to the International Space Station

The seven crew members on space shuttle Discovery are spending their last day in space packing away equipment and making final preparations to come home.

The crew will also speak with students at a school in Hawaii on Friday, as two of the team are former teachers.

Discovery launched on 15 March, docking with the International Space Station (ISS) to deliver new solar panels.

The shuttle is scheduled to land at Kennedy Space Center in Florida on Saturday afternoon.

The shuttle will return with Sandra Magnus on board, who has been stationed at the ISS for four months.

As Discovery heads toward Florida, the Soyuz capsule launched onThursday is on its way to take Discovery's place at the space station.

On the tiles

The shuttle undocked from the space station on Wednesday after eight days there.

The crew spent five hours on Thursday inspecting the shuttle's outer surface using a laser and camera mounted on a 50-foot boom connected to Discovery's robotic arm.

The shuttle, as seen from the ISS, includes a novel heat-shield tile

The images were then sent back to Mission Control as part of a routine procedure that ensures the integrity of the shuttle's heat-shield tiles.

The tiles are designed to dissipate heat as the shuttle returns to Earth through an increasingly thicker atmosphere.

Under the shuttle's left wing is a single tile that includes a "bump", which interrupts the normally smooth airflow around the tiles.

The disrupted airflow will increase the temperature of the tiles around it by a small amount and is part of a test of candidate tiles for future missions.

Current designs for those missions mean spacecraft will ensure significantly more heat on re-entry than the space shuttles, which might be retired next year.

"We have returned to using the space shuttle as a research vehicle," said Nasa shuttle programme manager John Shannon.

"We're trying to learn more and more about space flight and hypersonic re-entry."

On the ground, Nasa is preparing space shuttle Atlantis to be rolled out toward the launch pad on 31 March.

Atlantis is scheduled for a 12 May launch for the Hubble Telescope's final servicing mission, which has been delayed since October 2008.