The space shuttle Atlantis is preparing for the final mission of the US shuttle program next month. Atlantis's crew is excited and reflective before the space craft's last flight.

The crew, led by mission commander Christopher Ferguson, met the media Wednesday at the Kennedy Space Center in Florida. Ferguson, a retired US Navy Captain said he and his crewmates feel a special obligation to do well.

"I think, and we have not talked about this, I think each of us feel a little extra burden to make sure we put on the best possible face forward for the last go around of this, and the crew is very prepared," said Ferguson. "We are going to go out and do a very fantastic job."

Ferguson, Pilot Doug Hurley and mission specialists Sandy Magnus and Rex Walheim will deliver spare parts and supplies to the International Space Station during their flight. Atlantis will also test whether it is possible to robotically refuel orbiting satellites during its 12-day mission.

The shuttle will return with a failed ammonia pump module to help NASA better understand the failure mechanism and improve pump designs for future systems.

Atlantis is scheduled to lift off on July 8 and land in Florida on July 20. Ferguson says he expects the final landing to be a poignant moment for everyone involved with the shuttle program.

"Like I said, when it is all over at the very end I think that is when the enormity of it is going to hit us," added Ferguson. "You know that last wheel stop call is going to be a little tough."

The mission is the last of the US Space Shuttle program. During its 30-year-history the shuttle fleet - Columbia, Atlantis, Challenger, Discovery, and Endeavour - has logged more than 825 million kilometers of space travel. The first shuttle, Enterprise, never flew in space.

Two of the shuttles - Challenger and Columbia - and their crews were lost. Challenger exploded during launch in January of 1986. Columbia disintegrated just minutes before landing in February of 2003.

NASA expects to start testing the shuttle's replacement, the Orion spacecraft, with astronauts on board sometime in 2013.

ammonia: a colourless gas with a strong smell; a clear liquid containing ammonia, used as a cleaning substance 氨；氨水

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（来源：VOA 编辑：崔旭燕）