The Space Shuttle Discovery sits on Launch Pad 39B at the Kennedy Space Center at Cape Canaveral, Florida
The U.S. space agency NASA has begun its countdown to what it expects will be a successful launch next week of the Space Shuttle Discovery on the first such mission since the Columbia shuttle disaster.

NASA Test Director Pete Nickolenko told reporters at the Kennedy Space Center in Florida that officials believe the flight systems and ground support systems are ready.

He said the seven crew members, who returned to the space center Friday, are excited and ready to blast-off Tuesday for the 12-day mission.

A planned launch earlier this month was postponed by a faulty fuel sensor that officials say was likely caused by an electrical grounding problem.

No shuttle has flown since February, 2003 when the Shuttle Columbia broke apart while re-entering Earth's atmosphere, killing all seven astronauts.