The Discovery launch was originally scheduled for February 12, but was postponed six times due to problems with hydrogen valves, which cut the duration of the current shuttle mission by one day to 13 and the number of spacewalks from four to three.
The shuttle is carrying a crew of seven, including Japanese Aerospace Exploration Agency astronaut Koichi Wakata, and will deliver the space station's fourth and final set of solar array wings. The wings will provide the electricity to fully power scientific experiments and support the station's expanded crew of six in May.
Wakata, who is to become the first long-duration Japanese resident of the ISS, will replace U.S. astronaut Sandra Magnus, who has been aboard the space station for more than four months. The Japanese astronaut will return to Earth during the next station shuttle mission, STS-127, scheduled for June 2009.
The 13-day mission will feature three spacewalks to help install the S6 truss segment to the starboard, or right, side of the station and the deployment of its solar arrays. The flight also will replace a failed unit for a system that converts urine to potable water.
