US space shuttle returns to Earth

Nasa's space shuttle Discovery has landed at the Edwards air force base in California.Plans to land at the Kennedy Space Center in Florida were postponed due to bad weather.The shuttle missed two landing slots on Thursday, before landing at 1753 PDT on Friday (0053GMT Saturday).The shuttle had been on a supply mission to the International Space Station (ISS) with seven astronauts on board."We're very happy to be back on land here in California," mission commander Rick Sturckow said. "It was a great mission."

Nasa tries to avoid landings in California, because the shuttle must then be transported back to Florida, which takes more than a week and costs $1.7m.Discovery took a furnace and freezer up to the station for use in science experiments.

It also delivered a new sleeping compartment, an air purification system and a treadmill to help maintain astronauts' health.

In addition, Discovery dropped off US astronaut Nicole Stott for a three-month stay on the platform, picking up colleague Tim Kopra for the ride home. Kopra has been living on the ISS for the past 44 days.Three spacewalks were conducted during the mission. The exterior work included the replacement of an exhausted ammonia tank. Ammonia is used in the station's cooling system.Cabling was also laid in readiness for the arrival early next year of another module.

This new "room" will have a large window attached to it. The Cupola, as it is known, is expected to give crewmembers the perfect vantage point from which to control future robotic operations on the outside of the ISS.The US space agency plans six further shuttle flights to the ISS before retiring its re-useable spaceship fleet at the end of next year or early in 2011.

-BBC