The U.S. space agency, NASA, is making final preparations for the planned launch of the space shuttle Atlantis on Sunday.
The shuttle's crew arrived at the Kennedy Space Center in Florida Thursday morning for the mission to bring a truss to the International Space Station. Installation of the 17-ton truss will mark the first time in nearly four years that construction work on the station will be carried out.
Atlantis's payload manager Robbie Ashley says the work has "been a long time coming."
The crew plans to take three spacewalks during the stay. In addition to adding the truss, astronauts will install a second set of solar panels, doubling the space station's ability to produce energy.
NASA spokesman Steve Payne says preparations for the launch are going smoothly and that the Atlantis shuttle is in excellent shape. Weather conditions for Sunday's launch look favorable.
This will be the second shuttle fight this year. The shuttle Discovery carried out a successful mission to the space station in July.
Its safe return was a milestone for the U.S. space program, which has been plagued by safety concerns since the shuttle Columbia disintegrated as it returned to earth in 2003, killing all seven astronauts on board.