Atlantis to undock from ISS on final mission

The US space shuttle Atlantis prepared to undock from the International Space Station Sunday after delivering tons of supplies on the final mission for the 25-year-old spacecraft.

The crews of both spacecraft were scheduled to bid their farewells and close the hatch closure shortly after 8:00 am (1200 GMT), NASA officials said.

Undocking is set for 11:22 am (1522 GMT).

On Friday, Atlantis astronauts Garrett Reisman and Michael Good completed the mission's final spacewalk at the station that lasted six hours and 46 minutes.

The pair plugged a new ammonia jumper cable into the orbiting space station's huge framework and installed two new batteries that store energy collected by the station's large solar panels.

Each battery weighs 375 pounds (170 kilograms) and measures about the size of a three-foot (one-meter) box. The astronauts swapped out another four batteries during another spacewalk on Wednesday.

Batteries usually last five to six years but the ones that were replaced had functioned for nine years. The old batteries will be brought back to Earth aboard Atlantis.

During their spacewalk, Good and Reisman also transferred a grapple fixture from the shuttle to the station and reconfigured some tools.

During the 12-day mission, Atlantis and its six-member crew unloaded over 12 tons of equipment, including the communications antenna, power storage batteries and a radiator.

The biggest single element is the five-ton Rassver research module, or MRM-1, which will provide additional storage space and a new docking port for Russian Soyuz and Progress spacecraft.

The Rassver -- "Dawn" in Russian -- was permanently attached to the bottom of the space station's Zarya module. It carries important hardware on its exterior including a radiator, airlock and a European robotic arm.

The Sunday undocking caps the shuttle's 25-year career during which it has logged some 115 million miles (185 million kilometers). It is due back in Florida on Wednesday at 8:44 am (1244 GMT).

Only two more shuttle launches remain -- one in September for Discovery and the final blast off for Endeavour in November -- before the curtain falls on this era of human spaceflight.

The United States will then rely on Russia to take astronauts to the station aboard three-seater Soyuz spacecraft until a new fleet of commercial "space taxis" is operational.