Washington  - The space shuttle Discovery landed safely at the Kennedy Space Centre in Florida on Saturday. Commander Lee Archambault guided the shuttle to a picture-perfect landing at 1914 GMT, ending the shuttle's 13-day mission to the International Space Station.

"Welcome home after a mission to bring the ISS to full power," the NASA ground crew said, adding a special welcome to astronaut Sandra Magnus, who returned to Earth after spending 129 days living aboard the ISS.

"Thank you very much. It's good to be back home," Archambault replied.

The landing had been delayed by around an hour and a half due to poor weather from an originally scheduled 1740 GMT touchdown, due to thick cloud cover.

The shuttle did face some strong headwinds as it came in for the landing, but Archambault said after landing that "The shuttle was very easy to fly and rock steady in all that turbulence."

The mission astronauts installed a fourth set of solar panels on the ISS, completing the power plant needed to double the station's electrical generating capacity. The power allows the station to sustain six long-term residents instead of the current crew of three, the crew could be expanded as early as May.

After the landing, Bill Gerstenmaier, associate administrator for space operations, praised the completion of ISS.

"If you look at that station, not one country could accomplish what's going on on space station. It really took all the countries working together," he said, noting that ISS illustrates international cooperation in space and its potential in advancing scientific research.

The astronauts who installed the solar wings said it was inspiring to see the station with a full set of wings as it has been envisioned since the beginning.

"The pictures never do the view justice and it was the exact same backing away from the space station," said Tony Antonelli, who had an excellent view as he manoeuvred the space shuttle away from the station.

The shuttle crew completed three spacewalks during its mission, including installation of the last solar panels.

Earlier Saturday, a Russian Soyuz craft docked at the ISS, bringing two more ISS crew members and space tourist Charles Simonyi, a co-founder of Microsoft taking his second flight in space.

Cosmonaut Gennady Padalka and US astronaut Michael Barratt will replace Yury Lonchakov and commander Mike Fincke. They will join Japanese astronaut Koichi Wakata, the first long-term Japanese crew member on the ISS, who arrived aboard the Discovery.

Magnus, Wakata's predecessor on the ISS crew, returned home with the Discovery. NASA administrators said hours after the landing, she was in "good shape and great spirits."

The shuttle is also carrying scientific experiments conducted aboard ISS and samples from a machine designed to turn urine and sweat into drinkable water.

Discovery delivered a new machine after an earlier version kept breaking on an earlier shuttle mission. NASA will take about a month to analyze the sample to make sure the water is safe before the expansion of the ISS crew to six.

The Soyuz docking came two days after the Soyuz was launched from the Baikonur centre, went without a hitch and was completed at 1305 GMT, nine minutes earlier than scheduled.

Simonyi is to return to earth on April 7 along with Fincke and Lonchakov. The Hungarian-born Simonyi, 60, who made his fortune as a software developer, is making his second trip to space as a tourist.

By his own account, Simonyi paid 35 million dollars for this trip into space, some 10 million dollars more than during his first one two years ago.

Simonyi looks to be the last of the space tourists to be allowed on the ISS for the foreseeable future, with the station set to be filled to its maximum capacity of six crew members in May.

Then, a trio of additional astronauts will join the ISS, with Belgian astronaut Frank de Winne to become the first European Space Agency commander of the ISS.