NASA postpones spacewalk until Friday

NASA has postponed for one day a spacewalk by two crew members from the Discovery space shuttle, pushing it back from on Thursday to Friday, US space officials said.

They said the spacewalk, the fourth of this current mission, will focus on repairing a panel torn on Tuesday on one wing of a solar array.

"The flight control team has just informed the crew that the mission's fourth spacewalk is now targeted for Friday.

"The spacewalk will be focused on the solar array wing," the US space agency said in a statement on Wednesday.

The solar panel on the International Space Station ripped as the antenna was deployed on Tuesday.

The solar antenna, which has wings measuring 76 meters when unfurled, was repositioned after astronauts earlier successfully installed a massive truss that is used to rotate the energy-generating solar arrays.

NASA estimated the tear in the panel to be about 90 centimeters, but said the solar antenna nevertheless has been providing about 97 per cent of the energy it supplies to the space station.

The solar array is critical to providing power for the European Laboratory scheduled for delivery in December.

Another solar array is crippled by a malfunctioning rotary mechanism which was supposed to have been repaired during the spacewalk originally scheduled for Thursday.