(Reuters) - The U.S. space shuttle Discovery landed safely at its home base in Florida on Tuesday, wrapping up one of NASA's last cargo runs and servicing missions to the International Space Station.

After 15 days in space and a journey of 6.2 million miles (9.9 million km), the shuttle touched down at the Kennedy Space Center's runway at 9:08 a.m. EDT (1308 GMT), following landing delays on Monday and earlier Tuesday due to poor weather.

"Welcome home," astronaut Rick Sturckow from Mission Control in Houston radioed to Discovery commander Alan Poindexter. "Congratulations to you and the crew on an outstanding mission."

"Thanks for those words," replied Poindexter. "What a great mission. We enjoyed it and we're glad that the International Space Station is stocked up again."

Discovery and its seven-member crew returned from a 10-day stay at the space station, a $100 billion project of 16 nations that has been under construction since 1998.

The final leg of Discovery's flight, the 131st in the history of the shuttle program, was visible across much of the United States, a path NASA usually avoids to save fuel and to skirt potentially hazardous high-altitude ice clouds.

With extra fuel and no concerns about hitting ice clouds at this time of year, NASA opted for the northwest-to-southeast approach, a flight plan that gave the shuttle crew a little extra time to work at the space station.

If skies were clear, residents from Helena, Mont., to Montgomery, Ala., and south into Gainsville, Fla., could see a plasma trail or glowing cloud, depending on the light, as the shuttle made its supersonic glide back to Cape Canaveral.

NASA has just three shuttle flights remaining to deliver large spare parts to the space station and complete its assembly before the shuttle fleet is retired later this year.


Russian, European and Japanese cargo ships will resupply the station after the shuttles are retired.

Next year, NASA hopes to turn over the bulk of its station cargo flights to two U.S. firms, Space Exploration Technologies and Orbital Sciences Corp., which hold contracts worth $3.5 billion to deliver supplies to the orbiting outpost.

Russian Soyuz capsules have already become the sole means for ferrying crewmembers to and from the station, a service that costs the United States $51 million a seat.

U.S. President Barack Obama wants to spend $6 billion over the next five years to help U.S. firms develop space taxi services so the country won't have to depend on the foreign transport.

Discovery delivered to the space station a cargo pod, about the size of a small bus, filled with equipment and experiment racks, a fourth U.S. sleeping berth, a darkroom for the station's U.S. laboratory module and other supplies.

The returning Italian-built cargo pod was packed with old equipment and items no longer needed on the station. The shuttle also hauled home a spent tank of ammonia coolant, which will be refurbished and returned to the station as a spare.

A new ammonia tank was installed during three spacewalks by Discovery astronauts Rick Mastracchio and Clay Anderson, but a problem with a valve prevented NASA from activating the coolant system as planned.

The International Space Station has two coolant loops, and both will need to be operational within about a month to keep the station at full power as the changing sun angle generates more heat on the station.

The repair work, which will require a spacewalk, is expected to be turned over to the resident space station crew, which includes two U.S. astronauts, three Russian cosmonauts and an astronaut with Japan's space agency.

The station crew also will be preparing the outpost for a new Russian docking compartment, scheduled to be launched aboard shuttle Atlantis on May 14. NASA plans to move Atlantis to the launch pad on Tuesday night in preparation.