By Paul Rincon
BBC News science reporter, Houston
The first spacewalk lasted about seven hours
Nasa is considering whether to send an astronaut out on a spacewalk to trim two protruding gap fillers on the underside of space shuttle Discovery.
They are currently looking at the best option for getting a crew member to the underside of the vehicle safely.
One option would be for a crew member to be ferried to Discovery's belly by the International Space Station's robotic arm.
Gap fillers plug the spaces between shuttle heat shield tiles.
The fillers are made of ceramic fabric
Dangling materials
Shuttle managers hope to come to a decision over the gap filler issue on Monday.
"We have a team of folks working aggressively to go and make that gap filler safe if we decide it's an issue. We have a separate team looking at the effects of leaving that gap filler protruding," said mission flight director Paul Hill.
They are also deliberating over which is the better option to repair the gap fillers.
http://news.bbc.co.uk/2/hi/science/nature/4733495.stm