NASA counts down toward Saturday shuttle launch

NASA is counting down toward the weekend launch of space shuttle Endeavour.

The countdown clocks began ticking Wednesday morning. Endeavour is slated to blast off Saturday on a space station construction mission. Forecasters put the odds of good launch weather at 90 percent.

The flight comes less than three weeks after NASA's last shuttle trip involving the successful overhaul of the Hubble Space Telescope. The highlight of this 16-day mission will be the completion of a huge Japanese lab.

It will mark the first time 13 people are together in space at the same time. Six people now live at the space station; they will be visited by seven shuttle astronauts.