With pilot Paul Lockhart at the controls, the shuttle Endeavour undocked from the international space station today, leaving a fresh three-man crew behind and ending seven days of work to install and activate a new solar array truss segment.

Powerful springs gently pushed Endeavour away from the station's docking collar at 3:05 p.m. EST as the two spacecraft sailed into sunlight 248 miles above western Australia.

"Houston, physical separation," an astronaut radioed as the shuttle pulled away at a relative velocity of a tenth of a foot per second.

Lockhart guided the shuttle to a distance of 400 feet or so directly in front of the station before looping up to a point directly above the lab complex. At that point, the pilot fired the shuttle's maneuvering jets to leave the area for good.

Total duration of joint operations with the space station, from the point hatches were opened last Monday until the last hatch was closed today, was six days 18 hours and 26 minutes.

Earlier today, the new crew of the station, flanking the hatch leading to the shuttle Endeavour, bid the departing Expedition 5 crew farewell, promising to "take good care" of the station.

Expedition 6 commander Kenneth Bowersox, flight engineer Nikolai Budarin and science officer Donald Pettit embraced the shuttle's four astronauts and the three departing Expedition 5 crew members, one at a time, as they left the station around 12:15 p.m.

"Try to keep your sense of humor," shuttle skipper James Wetherbee told Pettit.

"Oh, I will," Pettit said. A few moments later, the rookie science officer told Expedition 5 commander Valery Korzun: "Thanks for the good handover. We promise to take good care of the space station.

A few moments later, the two crews began closing the final hatch between the shuttle and the lab complex. Bowersox told ground controllers "this is a big moment for us, getting ready to send these folks off."

"It's been so much fun serving with them the last few days, we've been working like one big gigantic crew and I couldn't have anticipated how smooth and how well we've been able to work together," he said. "And we're going to miss them while they're gone."

About two hours after undocking, the Endeavour astronauts launched a pair of tiny Air Force "picosats", the latest test of technology that one day may be used in small satellites built to monitor or inspect other spacecraft. The box-shaped MEPSI satellites, connected by a 50-foot tether, were launched from a canister in the forward part of the shuttle's cargo bay at 5:05 p.m.

Television from the shuttle showed the devices, propelled by a spring mechanism, shooting out of their canister at a relatively high rate of speed, quickly disappearing from view.

"For us, we're going to actually show that this little system of two pico satellites, or micro satellites, can be deployed properly and that they will function together as one," Lockhart said in a NASA pre-flight interview. "They're tied together with a cord and so they're interested in the capabilities of the thing being deployed properly, that the physics of it being in orbit doesn't cause the two micro-satellites to behave improperly and then just to show in a gradual increase of capability that these little micro-satellites can be functioning properly.

"So on our flight, I basically get to deploy one of these and then we're just going to film them as they move on up and then they're going to be transmitting the data back down to the ground."