According to NASA, the undocking took place at 11:55 p.m. EDT ( 0355 GMT Monday) as the spacecraft sailed 215 miles (346 km) above Bolivia.

    Pilot Greg Johnson, at the aft flight deck controls, flew Endeavour in a circle around the station at distances of about 450 to 650 feet. Crew members took still and video images of the station.

    As Johnson was about to begin the flyaround, Commander Mark Kelly radioed mission control that he could see the two-billion-U. S.-dollar Alpha Magnetic Spectrometer (AMS) particle physics detector Endeavour had brought to orbit. "It's a new day for science on the space station," he said to mission control.

    The AMS will be left at the space station to scour the universe for clues about dark matter and antimatter. Endeavour is scheduled to land at the Kennedy Space Center at 2:35 a.m. (0635 GMT) on Wednesday.

    During their stay at the space station, the Endeavour crew conducted four spacewalks to complete construction of the U.S. side of the 100-billion-dollar outpost, a project of 16 nations that has been being assembled in orbit since 1998.

    They also brought up a logistics carrier with spare parts and performed some maintenance and installation work during the four spacewalks, the last to be carried out by an American shuttle crew.

    NASA plans to decommission Endeavour, its youngest shuttle with 25 voyages, and send it to a museum in Los Angeles for display.

    NASA's 30-year-old shuttle program is ending due to high operating costs. The Obama administration wants to spur private companies to get into the space taxi business, freeing NASA to focus on deep space exploration and new technology development.

    When the U.S. space shuttle program officially ends later this year, the Russian space program's Soyuz capsule will be the only method for transporting astronauts to and from the space station.(本文由在线英语听力室整理编辑)