FACTBOX: Space shuttle Discovery's mission

(Reuters) - The U.S. space shuttle Discovery lifted off on Saturday with the second segment of Japan's space laboratory, its primary contribution to the International Space Station.

Here's a look at what's planned during the 123rd shuttle flight, the third of five missions scheduled for this year:

* Deliver and install the 37-foot, 32,000-pound (14,520-kg) main section of Japan's Kibo pressurized science laboratory to the space station. The first section, a storage compartment stuffed with computers and gear, was carried into orbit by shuttle Endeavour in March.

* Move Kibo's storage compartment from its temporary resting place on top of the space station's Harmony connecting node to its permanent place on the Kibo lab.

* Install television cameras on the outside of Kibo and power up the lab to make it ready to support the station's crew. Astronauts will enter the new lab wearing protective masks and goggles until the air in Kibo has been cleansed by equipment on the station.

* Activate and test new Japanese robotic arm.

* Retrieve the boom used to inspect the space shuttle's heat shield for damage. It was left at the station during the last mission and will be brought back to Earth by Discovery.

* Fix the space station's toilet; inspect and repair a rotary joint on a solar wing panel that sustained unexplained damage last year.

* Deliver astronaut Greg Chamitoff, who will remain on the International Space Station, replacing flight engineer Garrett Reisman, who will return to Earth aboard Discovery.

(Source: NASA web site, Reuters) (Reporting by Irene Klotz in Cape Canaveral; Editing by Jim Loney and Bill Trott)