This story was updated at 4:07 p.m. EDT.
NASA has begun counting down toward the last launch of thespace shuttle Atlantis. The countdown picked up at T-43hours today at 4:00 p.m. EDT (2000 GMT).
The countdown will take some breaks over the next few daysfor built-in holds in the schedule. Atlantis is slated to lift off for its 32ndand finalmission Friday at 2:20 p.m. EDT (1820 GMT) from Launch Pad 39A at KennedySpace Center (KSC) in Cape Canaveral, Fla. The shuttle will carry sixastronauts, a new Russian research room, and a set of spare supplies to theInternational Space Station.
"Everything is going quite well at Pad A," NASAtest director Steve Payne said during a Tuesday briefing. "Work continueson schedule as we prepare Atlantis for her 32nd flight."
The weather outlook is promising for a Friday afternoonblastoff, shuttle weather officer Kathy Winters said.
"Overall, weather looks favorable," she said."There's just a 30 percent chance of KSC weather prohibiting launch,mainly for concern over a low cloud ceiling."
If the launch does happen to be delayed for any reason, NASAcan try again to loft the shuttle through May 18. After that the shuttle muststand down temporarily to let an unmanned Delta 4 rocket carry a GPS satelliteto orbit.
The weather forecast is similar for Saturday and Sunday,with a 70 percent chance of good conditions expected as on Friday.
Mission managers said this last mission of Atlantis ? thefirst of the final three shuttle flights ever before the fleetis retired later this year ? will be especially meaningful for them.
"It is one of those moments where people do kind ofcontemplate on what we've been doing for the last few years," Payne said."We're making a point of savoringthe moment while we can, because this has really been a privilege for us towork out here and be associated with this program."
Atlantis, led by commander Ken Ham, is scheduled to spend 12days in space. Its main payload is the Russian Mini-ResearchModule-1 (MRM-1), also called "Rassvet" (which means"Dawn" in Russian).
"The MRM-1 is installed on the payload bay," saidRobby Ashley, STS-132 payload manager. "It'll be joining MRM Number 2,which is already on orbit."
Also packed in Atlantis' payload bay is a set of six replacementbatteries that will be swapped out with aging ones currently on the station.
"These batteries have a six-and-a-half year designlife, and they've been up there a lot longer than that," Ashley said.
Finally, the shuttle will deliver a new space-to-groundantenna that will serve as an active backup antenna to one currently in use.
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