Washington - The US space shuttle Discovery is set to land back on Earth on Friday night, following another postponement due to bad weather. The shuttle will aim to land at 1048 GMT, in Cape Canaveral in Florida.
NASA had already cancelled two provisional landing times on Thursday night. The shuttle had had to avoid a piece of space junk on its flight to Earth, the space agency said.
Due tostormy weather forecasts, four possible landing slots have been prepared, including Friday night's.
If the first landing attempt is unsuccessful, the shuttle will divert for further attempts to the Edwards air force base in California.
In total, four landing times have been planned between Friday night and Saturday afternoon.
NASA experts do not yet know what the object was that caused one of the delays, but believe it may be something that was lost on the mission's third space walk, reported CNN.
The Discovery, which has seven astronauts on board, has enough supplies and energy to last in orbit until Sunday. NASA would prefer to have the shuttle land in Florida. A landing in California would mean high transportation costs back to the Kennedy Space Centre.
The Discovery's launch was also delayed three times because of bad weather and technical problems.
The astronaut's main task on the two-week journey was to fit out the International Space Station (ISS). The astronauts performed three space walks. They replaced an old ammonia coolant tank, laid cables and installed two new GPS antennae. A new laboratory, an experimental sample freezer and several sleeping cabin for Japan's Kibo laboratory were also transported.
