WASHINGTON, Sept. 8 (Xinhua) -- After eight days together in orbit, U.S. space shuttle Discovery, with seven astronauts aboard, undocked from the International Space Station (ISS) on Tuesday, beginning its journey back to Earth.

    According to NASA TV, the undocking took place at 3:26 p.m. EDT(1936 GMT) as the two craft soared over China. After safely separated from the orbiting complex by about 450 feet, Discovery's mission pilot Kevin Ford conducted a fly around of the space station. The maneuver provides an opportunity to get video of the station that can be used to inspect for damage or general condition of the vehicle's exterior. A final separation burn is expected at 5:09 p.m. EDT (2109 GMT).

Space Shuttle Discovery Commander Rick Sturckow (L) and International Space Station Expedition 20 Commander Gennady Padalka (R) shake hands during farewell ceremonies between the crew of the two spacecraft aboard the International Space Station in this image from NASA TV September 7, 2009. (Xinhua/Reuters Photo) Photo Gallery>>>

    Later, the shuttle crew will again engage the shuttle robotic arm, its extension boom and cameras for a last look at the thermal protection system to check for any damage.

    Discovery lifts off midnight on August 28 from the Kennedy Space Center in Florida after two delays. Its 13-day flight is scheduled to end with a landing back in Florida on Thursday.

    Discovery delivered tons of supplies and equipment to the ISS, which included science and storage racks, a freezer to store research samples, a new sleeping compartment and the COLBERT treadmill.

    The 1,600-pound (726 kg) freezer, developed by the European Space Agency, was installed in Japan's Kibo laboratory.

The Space Shuttle Discovery is seen docked to the International Space Station with the Earth in the background in this image from NASA TV September 7, 2009.(Xinhua/Reuters Photo) Photo Gallery>>>

    The sleeping compartment is the third U.S.-built sleeping berth for the station crew, bringing the total number of bedrooms in the station to five. A sixth and final crew cabin is scheduled to arrive next year.

    NASA selected the treadmill's name after comedian and host Stephen Colbert of Comedy Central's "The Colbert Report" took interest during the ISS's Node 3 naming poll and urged his followers to post the name "Colbert," which received the most entries. The treadmill will be the second on the station.

    Discovery's 13-day mission also included three spacewalks to replace experiments outside the European Space Agency's Columbus laboratory, and install a new liquid ammonia storage tank and return the used one. Ammonia is used to move excess heat from inside the station to the radiators located outside.

    Six more shuttle flights are planned over the coming year to complete the construction of the ISS. The launch of the next shuttle, Atlantis, to the ISS is scheduled for November.

The Leonardo logistics module is shown as it is returned to the Space Shuttle Discovery's payload bay with horizon of the Earth in the background in this image from NASA TV September 7, 2009.(Xinhua/Reuters Photo) Photo Gallery>>>

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