NASA is counting down toward Sunday's launch of space shuttle Endeavour.
The countdown clocks began ticking early on Thursday. Endeavour and a crew of six are all set to deliver a new room to the International Space Station. They're also taking up a dome with seven windows that will serve as an unprecedented lookout. Forecasters put the odds of good weather at 70 per cent. Launch time is 4:39 am.
The astronauts will be working the graveyard shift during the 13-day mission. Everything _ all three spacewalks, and the docking and undocking of the shuttle _ will take place late at night or in the wee hours.
This will be the last major construction mission at the space station, which is almost complete.