Shuttle leaves space station to begin trip home

CAPE CANAVERAL: Space shuttle Endeavour departed the International Space Station late on Sunday, clearing the way for a final cargo run to the outpost before NASA retires its three-ship fleet.

As the spacecraft sailed 215 miles/346 km above Bolivia, pilot Greg Johnson gently pulsed Endeavour's steering jets at 11:55 p.m. EDT to back away from the docking port that has anchored the shuttle since its arrival on May 18.

Endeavour delivered the station's premier science experiment -- the $2 billion Alpha Magnetic Spectrometer particle detector -- and a pallet of spare parts intended to tide over the orbital outpost after the shuttle program ends.

"Endeavour departing," radioed station flight engineer Ron Garan. "Fair winds and following seas, guys."

"Thanks Ron," replied Endeavour commander Mark Kelly. "Appreciate all the help."

Before leaving the station's orbit, the shuttle crew planned to test a new automated rendezvous system being developed for NASA's next spaceship, the Multi-Purpose Crew Vehicle, intended to fly astronauts to the moon, asteroids and eventually to Mars.

One final shuttle mission is planned before the United States ends the 30-year-old shuttle program. Atlantis is due to launch July 8 with a year's worth of supplies for the station, a contingency plan in case the commercial companies hired to take over supply runs to the station encounter delays with their new vehicles.

The shuttles are being retired to save the $4 billion annual operating expenses so NASA can develop new vehicles that can travel beyond the station's 220-mile-high/355-km-high orbit.

During its 12 days at the station, the Endeavour crew completed four spacewalks to complete construction of the US-side of the $100 billion outpost, a project of 16 nations that has been being assembled in orbit since 1998.

Endeavour is due back at the Kennedy Space Center in Florida at 2:35 a.m. EDT on Wednesday, the same day sister ship Atlantis is scheduled to reach the launch pad for NASA's 135th and final flight.

Copyright Reuters, 2011