endeavour leave space station
Endeavour's last mission is the penultimate flight for the 30-year US shuttle program, which will end for good after the Atlantis mission to the orbiting research lab in July.
The six-member crew of the Endeavour bid farewell to three astronaut colleagues on board the space station (ISS) and closed the hatches between the shuttle and station at 7:23 am (1123 GMT), NASA said.
The astronauts were to spend the afternoon sleeping in preparation for the late night undocking set for 11:55 pm (0355 GMT), NASA said.
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 June 1.The team spent a total of 10 days, 23 hours, and 45 minutes at the space station.
During that time, the crew delivered and installed a massive physics experiment, the Alpha-Magnetic Spectrometer-2, that 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 for the orbiting lab and performed some maintenance and installation work during four spacewalks, the last to be done 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, carrying its crew of five US astronauts and Italian Roberto Vittori.
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. STS-134 marks its 25th and final mission.
Endeavour is the sixth 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.