Endeavour carrying new part to ISS

The 'MBS' will move the space station's arm where needed

Workers at the Kennedy Space Center oversee the transport of the new Mobile Base System from one test stand to another.

(CNN) -- A major assembly job awaits the crew of the space shuttle Endeavour when it docks with the international space station next week.

Endeavour is scheduled to lift off Thursday, carrying a key component of the station, the Mobile Remote Servicer Base System, or "MBS."

The Canadian-built MBS is a 1,450-kilogram (3,190-pound) aluminum work platform designed to move along the space station's side rails. The station's robotic arm, Canadarm2, is to be attached to the MBS, enabling it to move laterally along the station's exterior, to transport equipment and supplies.

"The MBS gives a lot more freedom of range to Canadarm2," says John Dunlop, an assistant program manager on the system. "It will allow the arm to access considerably more of the station than it's currently able to when it's anchored on the lab."

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Attaching the arm to the MBS also means one end will always be free to carry components. Currently, the arm needs both ends free just to move along the station.

The MBS is also expected to serve as a work platform for astronauts on space walks.

During the shuttle's 12-day mission, astronauts Franklin Chang-Diaz and Philippe Perrin are scheduled to perform three space walks to attach the MBS to the station and connect power, data and video cables to it. They will also replace a joint on the robotic arm.

Endeavour is also to transport the "Expedition Five" crew -- Commander Valery Korzun and mission specialists Peggy Whitson and Sergei Treschev. The two Russian cosmonauts and American researcher-astronaut will remain aboard the station for four-and-a-half months, replacing the current Expedition Four crew.

"Expedition Five's ready to go up and take over," Whitson said when she arrived at Kennedy Space Center on Monday.