Space Shuttle Atlantis to Launch Tonight

Seven NASAastronauts are poised to launch into orbit tonight aboard the shuttle Atlantis tohaul vital new solar arrays to the International Space Station (ISS).

Commandedby veteran spaceflyer Rick Sturckow, Atlantis' STS-117 crew is set to rocketspaceward at 7:38 p.m. EDT (2338 GMT) from NASA's Kennedy Space Center inFlorida after months of delay.

"Thiscrew is very excited," Sturckow said this week of the planned space shot. "We'vespent a long time training for this mission."

Sturckowand his STS-117 crewmates will deliver a pair of massive, girder-like truss segmentsand new solar wings to the starboard side of the ISS during their planned11-day mission.

JoiningSturckow aboard Atlantis will be shuttle pilot Lee Archambault and missionspecialists Patrick Forrester, Steven Swanson, Danny Olivas, James Reilly andClayton Anderson. A late addition to the STS-117 mission, Anderson will stayaboard ISS to relieveNASA spaceflyer Sunita Williams as a member of the outpost'sExpedition 15 crew.

Weather forecastspredict an 80 percent chance of favorable conditions at liftoff today, though missionmanagers will keep a close watch for afternoon thunderstorms anticipated aroundAtlantis' Pad 39A launch site, Kathy Winters, NASA's shuttle weather officer,has said. ?

Longroad to launch day

Launch dayfor shuttle Atlantis comes after three months of delay prompted by a freakhail storm that damaged the orbiter's foam-covered fuel tank in late February.

Atlantiswas on track for a planned March 15 liftoff before the hail storm struck,etching thousandsof dents and divots into the foam insulation around the orbiter's 15-storyfuel tank. The damage delayed the STS-117 mission to allow time for engineersto perform an unprecedented repair job.

"Theteam is really pumped to get this done this time," NASA launch director MikeLeinbach said of today's planned launch. "Team Atlantis is ready togo."

While NASAshuttle missions have been delayed by hail damage before, the scale of repairwork for STS-117 -- engineers studied or patched up some 4,200 areas of damage-- outweighed those of past flights.

Bringingthe power

In additionto the Expedition 15 astronaut swap, the STS-117 crew plans to stage at leastthree spacewalks outside the ISS to install the outpost's new trusses and solararrays.

Weighing inat about 17.5 tons, the $367.3 million integrated Starboard 3/Starboard 4(S3/S4) truss segments are tipped at one end by two solar arrays that, onceunfurled next week, will have a wingspan of about 240 feet (73 meters).

The S3/S4 arraysare the third of four U.S.-built power plants bound for the ISS and are vitalfor the orbital laboratory's continued expansion. Once installed, the new solarwings will help provide enough power to support new modules andinternational laboratories scheduled for launch over the next eight months.

"Whatwe're doing is bringing up the starboard set of arrays," Reilly said in aNASA interview. "[T]hat's the foundation for the power supply that willnow allow us truly to become an integrated International Space Station with theEuropean and the Japanese labs."

During theSTS-117 mission, shuttle and ISS astronauts will also help coax an older solarwing into its storage boxes so its central truss segment can be moved during afuture spaceflight.

"Essentially,we are ready for launch and are excited to get into the final throes of thecountdown," Robbie Ashley, NASA's STS-117 payload mission manager, saidThursday. "It's an exciting time for the space station and for all ofus."

NASAwill provide live coverage of the launch of space shuttle Atlantis on NASA TVbeginning at 1:30 p.m. EDT (1730 GMT) today. Click here for SPACE.com's shuttle missionupdates and NASA TV feed.

• SPACE.com Video Interplayer: Space Station Power Up with STS-117
• STS-117 Power Play: Atlantis Shuttle Crew to Deliver ISS Solar Wings
• The Great Space Quiz: Space Shuttle Countdown
• Complete Shuttle Mission Coverage