CAPE CANAVERAL, Fla. -- Shuttle Endeavour departed the International Space Station on Saturday, leaving behind a fresh expedition crew, a new robot arm work platform and more than four tons of equipment and supplies.

STS-111

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With STS-111 pilot Paul Lockhart at the controls, the shuttle undocked from the outpost at 10:32 a.m. EDT (1432 GMT).

"Expedition Four, departing. Endeavour, departing," Expedition Five flight engineer Peggy Whitson called from within the Unity node as she rang the ship's bell, continuing a longstanding Naval tradition adapted for orbital use.

"Thank you, Peggy. Smooth sailing to you and your crew," replied Expedition Four flight engineer Dan Bursch, who is now a member of Endeavour's crew.

Undocking took place as the two ships circled Earth high above Kazakhstan, just west of the Baikonur Cosmodrome from which Russia launches its cosmonauts into orbit.

Slowly backing Endeavour away to a distance of about 450 feet (137 meters), Lockhart then flew the shuttle around the station in a victory lap of sorts, allowing the shuttle occupants to inspect and photograph the current state of the complex.

The maneuver also allowed Bursh and fellow Expedition Four crewmates Yuri Onufrienko and Carl Walz a final look at what has been their home for the past six months.

Then at 12:16 p.m. EDT (1616 GMT), Lockhart fired Endeavour's thrusters to officially begin a two-day journey back to Earth and a planned Monday landing at the Kennedy Space Center.

"Alpha, we wish you a very wonderful flight. We've completed our separation burn. We're heading home," said Endeavour commander Ken Cockrell.

"OK, thanks for the ride," Whitson replied.

The shuttle carried up Whitson and her Expedition Five crewmates of Valery Korzun and Sergei Treschev.

During the eight days Endeavour remained docked to the station, the Expedition Four and Five crews swapped positions and helped unload four tons of equipment and supplies from the Leonardo logistics module.

While that was going on, Endeavour spacewalkers Franklin Chang-Diaz and Philippe Perrin made three excursions outside to install a new work platform for the station's Canadian robot arm, as well as replace a faulty joint on that same arm.

Meanwhile, more than two tons of trash and unneeded equipment was packed up inside the Italian moving van for the trip home.

Endeavour's touchdown will mark the conclusion of a record-setting stay in space for astronauts Bursch and Walz.

Launched into orbit in December, the pair of Americans late Tuesday surpassed the previous U.S. spaceflight record of 188 days and four hours. Shannon Lucid held that mark thanks to a 1996 stay aboard the Russian space station Mir.

If shuttle Endeavour lands as scheduled on Monday, the new record for the longest American space mission will be 193 days and 17 hours.

About three hours before Saturday's undocking the 10 humans gathered in the Destiny science laboratory for a farewell ceremony that led to closing the hatches at 8:23 a.m. EDT (1223 GMT).

Before saying final goodbyes in a flurry of handshaking and hugs, the commanders of Expedition Four and STS-111 placed their mission stickers on a station wall and wished the new Expedition Five crew well.

With the two ships separated, both crews will be allowed some quiet time Sunday to unwind following a very busy week in space.

But first, the aboard Endeavour crew will run through the standard day-before-landing drill of checking out all of the equipment and shuttle systems they will require to execute the landing on Monday.

The pace of work aboard the outpost, meanwhile, will pick up again on Monday as the Expedition Five crew continue to settle in for their long duration stay.