HOUSTON — Discovery’s astronauts aimed for an early afternoon touchdown today to conclude a 15-day mission that saved a space station wing and allowed construction to continue at the orbiting outpost.

The weather forecast looked good by late morning for Discovery’s planned landing at Kennedy Space Center. But NASA was keeping an eye on clouds that were expected to move through the area around landing time.

Discovery is set for the first coast-to-coast re-entry by a space shuttle since the destruction of Columbia nearly five years ago.

The ship’s first landing path would take the crew over far western Canada, the Great Plains, and several Southern states. If bad weather or other problems force NASA to scrub the afternoon landing attempt, the shuttle’s second opportunity would include flying over several Western states, Texas, and Louisiana.

Mission managers decided yesterday that Discovery was safe for re-entry after examining the results of multiple thermal shield inspections.

Discovery blasted off October 23 on a mission that was considered the most challenging and complex in the nine years of orbital assembly of the international space station.

The crew delivered and installed a new pressurized compartment called Harmony, which will serve as a docking port for future laboratories, and moved a massive solar power tower half the length of a football field to the far left end of the station.

The mission took a dramatic turn, however, when one of the tower’s giant solar wings ripped in two places as the astronauts unfurled them after the move.

Saturday’s emergency repair of the torn wing was an unprecedented and daring feat whipped up by flight controllers in just a few days.

Standing at the end of a 90-foot robotically operated boom, spacewalker Scott Parazynski stretched his 6-foot-2 frame to cut the tangled wires that snagged the wing and install homemade braces.

He was farther from the safe confines of the station than any other astronaut had ever been, and he was mere inches away from the wing, which was coursing with more than 100 volts of electricity.

The historic repair effort allowed NASA to press forward with plans to launch the shuttle Atlantis in December to deliver a new European laboratory to the space station.

The torn wing was one of two space station power problems that emerged during Discovery’s visit. Steel shavings were found inside a rotary joint needed to turn another set of solar wings at the space station.