The US space shuttle Endeavour was on its way back to Earth on Monday after undocking from the International Space Station on its final journey before entering retirement, NASA said.

Endeavour's last mission is the penultimate flight for the 30-year-old US shuttle program, which will end for good after the Atlantis mission to the orbiting research lab, scheduled to begin July 8.

The undocking took place at 0355 GMT, when the space station and shuttle was 215 miles (350 kilometers) over La Paz, Bolivia, NASA said.

It was followed by a one-lap fly-around of the station to allow the crew to take photos of the space lab.

Endeavour fired its jets and began moving away from the station at 4:38 am (0838 GMT), the US space agency reported.

The six-member crew of the Endeavour -- five US astronauts and Italian Roberto Vittori -- bade farewell to three colleagues on board the space station (ISS) and closed the hatches between the shuttle and station at 1123 GMT Sunday.

Endeavour's 16-day mission began with the shuttle's launch from Cape Canaveral, Florida, on May 16 and will conclude when the shuttle lands back on Earth early on Wednesday.

During nearly 11 days at the space station, the crew delivered and installed a massive physics experiment, the Alpha-Magnetic Spectrometer-2, which will be left at the space station to scour the universe for clues about dark matter and antimatter.

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

A spacewalk is planned during Atlantis's mission in July but it will be done by space station crew, not astronauts who arrive aboard the US shuttle.

Endeavour is scheduled to land at Kennedy Space Center at 2:35 am (0635 GMT) on Wednesday.

The shuttle commander is Mark Kelly, whose lawmaker wife Gabrielle Giffords is recovering from a bullet wound to the head. The Arizona congresswoman was shot by a lone gunman during a meeting with local voters in January. Six people were killed.

Giffords was granted leave by her rehabilitation doctors to watch the launch from Kennedy Space Center along with other astronaut family members two weeks ago, but is not expected to return for the middle-of-the-night landing.

After the final shuttle missions, the three spacecraft in the flying fleet and the prototype Enterprise will be sent to different museums across the country.

Discovery, the oldest in the group, was the first shuttle to retire after its final journey to the ISS ended in March. Endeavour is the youngest, and flew its first space mission in 1991. It is now ending its 25th and final mission.

Endeavour is the sixth and last US space shuttle ever built, and was commissioned after the Challenger exploded in 1986.

The other original members of the fleet include Enterprise, a test model that never flew in space, and Columbia, which disintegrated on its return to Earth in 2003.

A total of 14 astronauts were killed in the Columbia and Challenger disasters.

With the US shuttle program closing, the world's astronauts will rely on Russia's space capsules for transit to the ISS at a cost of $51 million per seat until a new American spacecraft can be built by private enterprise, possibly by 2015.

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