Endeavour pulls away from the space station. Photo: NASA TV/Spaceflight Now

"Alpha, Endeavour, we have physical separation. We're executing the sep burn," called shuttle commander Kenneth Cockrell as the orbiter pulled away.

Following naval tradition, station engineer Peggy Whitson, nine days into a planned 132-day voyage, then rang the ship's bell aboard the lab complex, saying "Expedition 4 departing. Endeavour departing."

"Thank you, Peggy," outgoing flight engineer Daniel Bursch, a Navy captain, replied from Endeavour. "Smooth sailing to you and your crew."

With pilot Paul Lockhart at the controls, Endeavour slowly pulled straight away from the station, heading for a point about 450 feet directly in front of the lab complex. From there, Lockhart guided the shuttle through a lap-and-a-quarter photo-documentation flyaround of the outpost before firing Endeavour's maneuvering jets to leave the area for good a few minutes past noon.

"Alpha, we wish you a very wonderful flight," shuttle skipper Kenneth Cockrell radioed. "We've completed our separation burn, we're heading home. Enjoy yourselves while you're here."

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

Expedition 5 commander Valeri Korzun thanked Cockrell as well, jokingly telling him to "hit the road" when they land in Florida Monday.

"We'll hit the road and we'll try to hit it very gently," Cockrell promised.

The departing Endeavour as seen from the station. Photo: NASA TV/Spaceflight Now

The Endeavour astronauts took the afternoon off while mission managers at the Johnson Space Center took a preliminary look at the forecast for landing Monday. The weather looks generally favorable for Endeavour's planned 12:59 p.m. touchdown at the Kennedy Space Center, but showers may develop as the afternoon wears on.

"This flight could not have gone any better than it has," said lead flight director Paul Hill. "Tomorrow, the orbiter crew will be finishing up cabin stow and checking out systems for entry on Monday.

"We have been talking a little bit about weather. Right now, the weather looks good at KSC and the forecast our the first opportunity on Monday looks good. There's some concern that maybe some rain will come into the area after that. But we'll be watching it and the entry team will be on tomorrow and they'll be looking at weather."

Hill took a moment to reflect on Endeavour's mission and the successful repair of the international space station's robot arm. A third spacewalk to replace the arm's broken wrist joint was added to the mission flight plan in March. In the shuttle world, that amounts to a last-minute change, but spacewalkers Franklin Chang-Diaz and Philippe Perrin successfully changed out the joint Thursday during a seven-hour 17-minute spacewalk.

"About a hundred days before EVA-3 when we repaired the station arm was when we had the first indication we had a problem with the wrist-roll joint on the arm," Hill said. "And at that time, there were already a lot of folks here at JSC who know a lot about how we fly people in space, who thought we were biting off more than we could chew with his flight plan - with the logistics module, with the crew rotation and two EVAs. There were a lot of people really worried we had bitten off more than we could chew.

"Then here we came back a hundred days before we performed this EVA and stepped up to a third EVA, which had not yet been developed or planned. Looking back now the flight could not have gone better. ... It looked very easy, but it took a lot of smart people, a lot of hard work and they did a super job."

As of today, the space station has been continuously manned, by five different three-person crews, for 590 days. Expedition 4 commander Yuri Onufrienko, Daniel Bursch and Carl Walz were launched to the outpost Dec. 5. Assuming an on-time landing Monday, they will have spent 194 days off the planet, a new endurance record for U.S. astronauts.

The space station as seen by Endeavour during the flyaround. Photo: NASA TV/Spaceflight Now

Their replacements - Expedition 5 commander Korzun, Sergei Treschev and NASA biochemist Whitson - were ferried into orbit aboard Endeavour. They plan to remain in space until mid October when they will be replaced by yet another crew.

"I want to say to my space brothers, Dan Bursch and Carl Walz, thank you very much, you guys," Onufrienko said after mounting a mission patch on the wall of the Unity module. "I hope the new expedition will work here very successfully. Have a good time, guys."

Meanwhile, in a morning tagup with space station mission control, Bursch took a moment to bid farewell to Expedition 2 astronaut Susan Helms, who has been handling overnight CAPCOM chores during Endeavour's mission. Helms, an Air Force colonel, is resigning from NASA this summer to take on duties at Air Force Space Command in Colorado.

"We realize that today is your last shift in MCC and we would just like to express our sincere thanks and gratitude and also express our congratulations on just a wonderful, terrific career you've had at NASA," Bursch radioed. "We wish you the best of luck out in Colorado Springs and we'll miss you very much."

Said Walz: "It's been great working with you. ... Thanks for all your great tips for life on station, it really helped a lot."

Helms is a veteran of five space missions, logging more than 206 days in space and eight hours and 56 minutes of spacewalk time.

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