The Leonardo module's separation from the ISS was delayed

In preparation for the return flight to Earth, the Italian-built Leonardo logistics module was put back inside Discovery early on Sunday. The module had been temporarily attached to the ISS while five tonnes of equipment inside it were unloaded on to the platform.

However, a series of problems meant that the crew were running five hours behind schedule by the time Leonardo began separating from the space station.

The process of returning Leonardo to the shuttle was delayed in part by a hose leaking in a small compartment between the 21-foot module and the ISS.

Software problems

That slowed down a depressurisation procedure that had to be carried out before the module was unbolted using computer commands.

Susan Helms is part of the new crew

Discovery astronaut Andrew Thomas then used the shuttle's robotic arm to detach Leonardo and return it to the orbiter.

The crew earlier spent several hours testing software on two of the shuttle's computers that had been turned on too quickly.

This is not the first time the astronauts have suffered delays. An extra day has already been added to the mission because of difficulties experienced in filling Leonardo with rubbish and used station equipment.