WASHINGTON, Nov. 11 (Xinhua) -- The U.S. space shuttle Endeavour enters its official launch countdown at 10:00 p.m. EST on Tuesday (0300 GMT on Wednesday), aiming at a targeted launch on Nov. 14, NASA reported.

Crew members of the space shuttle Endeavour on Mission STS-126 arrive to prepare for launch at the Kennedy Space Center in Cape Canaveral, Florida Nov. 11, 2008. From left are Donald Pettit, Pilot Eric Boe, Mission Commander Chris Ferguson, Heidemarie Stefanyshyn-Piper, Robert Kimbrough, Steve Bowen and Sandra Magnus. The mission to the International Space Station is scheduled for Nov. 14.  (Xinhua/Reuters Photo) Photo Gallery>>>

    Liftoff is scheduled for Friday at 7:55 p.m. EST from Kennedy Space Center in Florida. Preparations on Endeavour are on schedule for the liftoff with officials reporting no technical issues standing in the way of a launch, said NASA.

    However, NASA Shuttle Weather Officer Kathy Winters gave the shuttle a 60 percent chance of meeting launch weather criteria for Friday's attempt. That falls to 40 percent chance of acceptable conditions on Saturday, but back up to a 70 percent chance of acceptable conditions on Sunday.

    A weather front that could produce thick clouds is expected to enter the KSC region on Friday or Saturday, Winters said. Under certain conditions, the clouds can be thick enough to prompt lightning concerns.

    Endeavour's seven crew members has arrived at KSC Tuesday afternoon. During the next few days, they will brush up on training and procedures while technicians and launch controllers monitor the final phases of preparations before liftoff.

    The seven astronauts are to fly Endeavour to the International Space Station on a 15-day mission to deliver about seven tons of new equipment and supplies, including a new kitchen and crew facilities for enlarging the station's resident capacity.

    Endeavour will also transfer a new crew member to the station and conduct four spacewalks to service the joints that turn the station's massive solar arrays.

    "This mission is all about home improvement," Commander Chris Ferguson said minutes after the crew landed at KSC. "Home improvement inside and outside the station."