Closing out a busy assembly mission, the Discovery astronauts, accompanied by outgoing station flight engineer Sandra Magnus, said farewell to the international space station's three-man crew today and floated out of the lab complex for the last time to rig the shuttle for undocking at 3:53 p.m.

Gathered in the Harmony connecting module in front of the port leading to Discovery, station commander Mike Fincke thanked shuttle skipper Lee Archambault and his crewmates for delivering a final set of solar arrays and other critical equipment, along with Magnus' replacement, Japanese astronaut Koichi Wakata.

"I'd like to say thanks to you and your crew for an outstanding mission," Fincke said. "You made the space station much better than it was before, you gave us more power ... you gave us a new crew member, you're giving Sandy a ride back home. You brought up some equipment we really needed for a six-person crew.

"That's what we were really hoping to get done with Expedition 18. And Sandy, the six-person crew, when they get up here (in late May), they're going to be thanking you for all your organization, all your hard work, the things that you built on board. You've done an outstanding job and I'd like to say thank you."

Launched aboard the shuttle Endeavour last November, Magnus is wrapping up a four-month stay aboard the station. Wakata plans to remain aboard the outpost until June when another shuttle will deliver his replacement.

Fincke and flight engineer Yury Lonchakov are scheduled to return to Earth on April 7 aboard the Soyuz TMA-13 spacecraft they rode into orbit last October. Their replacements - Expedition 19 commander Gennady Padalka and flight engineer Michael Barratt - are scheduled for launch Thursday at 7:49 a.m. EDT from the Baikonur Cosmodrome in Kazakhstan.

Padallka, Barratt and Wakata will be joined in late May by cosmonaut Roman Romanenko, European Space Agency astronaut Frank De Winne, a Belgian, and Canadian Space Agency astronaut Robert Thirsk, a shuttle veteran, boosting the station's crew size to six.

At a pre-launch news conference, Barratt, a former NASA flight surgeon, said the busy pace of crew exchanges and assembly missions, along with the planned increase to six full-time crew members, illustrates the growing maturity of the space station program.

"The requirement for a complex air traffic control system on the ground is a symbol of a vibrant and busy air transportation system, and I think it's exactly the same for us," he said. "It will make things a little bit harder, but I for one welcome this complexity. It's a sign of a vibrant space program and it's only going to get better - or worse! - depending on your point of view."

Assuming an on-time liftoff Thursday, the Soyuz TMA-14 craft carrying Padalka, Barratt and space tourist Charles Simonyi will dock with the space station Saturday morning, a few hours before Discovery's planned landing. Simonyi will return to Earth with Fincke and Lonchakov.

Aboard the station today, Fincke told the Discovery astronauts that saying farewell "is the toughest part of the mission, at least to me. On the one hand, it's a moment of triumph. And yet on the other hand, we're going to really be missing you. It was really great having you up here. All the things we got to talk about and do together, that's what the dreams in our lives are made of. So thank you everybody, thank you very much."

Archambault, in turn, thanked Fincke and Lonchakov, saying "we are very, very appreciative for the hospitality you all extended to us."

"You were very well prepared for us, you were happy to help us where we needed help and you were key and instrumental in getting three good EVAs (spacewalks) out the door and back in safely," Archambault said. "We're very proud to have left the space station with more power, hopefully power that for many, many years will provide very, very useful research to your future payloads."

Magnus floated across the "top" of the Harmony module above the heads of her shuttle crewmates. Wakata floated just below in the hatch leading to the European Space Agency's Columbus module.

"And Koichi, it's going to be tough to leave you," Archambault said. "You're always going to be a member of STS-119, you've done a lot of great work for us and I wish you the very best. We do look forward to seeing you back in Houston."

Finally, he added to Fincke: "you're an awesome commander. Best of luck. You've got just another couple of weeks here. Have happy travels and let's get together when you get back. Thank you very much."

The shuttle crew then floated through the docking port and out of sight into the space shuttle. Last to leave were Magnus and Archambault. The shuttle hatch was closed a few minutes later.

Additional coverage for subscribers:
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VIDEO: PREVIEW ANIMATION OF UNDOCKING AN FLYAROUND PLAY

VIDEO: SOYUZ MOVED TO LAUNCH PAD FOR EXPEDITION 19 PLAY
VIDEO: ROCKET HOISTED VERTICALLY ONTO LAUNCH PAD PLAY
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VIDEO: PRESIDENT OBAMA CALLS THE SPACE STATION PLAY
VIDEO: JOINT CREW IN-FLIGHT NEWS CONFERENCE PLAY
VIDEO: TUESDAY'S MISSION STATUS BRIEFING PLAY

VIDEO: FLIGHT DAY 9 HIGHLIGHTS MOVIE PLAY
VIDEO: MONDAY'S MISSION STATUS BRIEFING PLAY
VIDEO: SPACEWALKER RICK ARNOLD WORKS ON STATION ARM PLAY
VIDEO: SPACEWALKER JOE ACABA MOVES RAIL CART PLAY

VIDEO: FLIGHT DAY 8 HIGHLIGHTS MOVIE PLAY
VIDEO: SUNDAY'S MISSION STATUS BRIEFING PLAY
VIDEO: NEWS MEDIA INTERVIEWS WITH CREW PLAY

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VIDEO: SATURDAY'S MISSION STATUS BRIEFING PLAY
VIDEO: WALKTHROUGH OF SPACEWALK NO. 2 PLAN PLAY

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VIDEO: FRIDAY'S MISSION STATUS BRIEFING PLAY
VIDEO: NEWS MEDIA INTERVIEWS WITH CREW PLAY
VIDEO: SECOND SOLAR WING FULLY DEPLOYED PLAY
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VIDEO: FIRST SOLAR WING FULLY DEPLOYED PLAY
VIDEO: FIRST SOLAR WING DEPLOYED HALF-WAY PLAY
VIDEO: NARRATED ANIMATION OF SOLAR ARRAY DEPLOYMENT PLAY

VIDEO: FLIGHT DAY 5 HIGHLIGHTS MOVIE PLAY
VIDEO: THURSDAY'S MISSION STATUS BRIEFING PLAY
VIDEO: SPACEWALKER STEVE SWANSON RELEASES LOCKS PLAY
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VIDEO: STARBOARD 6 TRUSS HOISTED FROM PAYLOAD BAY PLAY
VIDEO: PREVIEW ANIMATION OF S6 TRUSS UNBERTHING PLAY
VIDEO: NARRATED TOUR OF DISCOVERY'S PAYLOAD BAY PLAY

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VIDEO: TUESDAY'S MISSION STATUS BRIEFING PLAY
VIDEO: SHUTTLE CREW WELCOMED ABOARD STATION PLAY
VIDEO: SPACE SHUTTLE DISCOVERY DOCKS TO SPACE STATION PLAY
VIDEO: SHUTTLE'S POINT OF VIEW DURING BACKFLIP PLAY
VIDEO: DISCOVERY PERFORMS 360-DEGREE BACKFLIP PLAY
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VIDEO: MONDAY'S MISSION STATUS BRIEFING PLAY
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VIDEO: LAUNCH REPLAY: CAMERA 009 PLAY
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VIDEO: ASTRONAUTS DON SPACESUITS FOR LAUNCH PLAY
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VIDEO: DISCOVERY IN THE PREDAWN DARKESS PLAY | HI-DEF
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VIDEO: THE PRE-LAUNCH NEWS CONFERENCE PLAY
VIDEO: ASTRONAUTS ARRIVE IN FLORIDA FOR LAUNCH PLAY
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VIDEO: INTERVIEW WITH COMMANDER LEE ARCHAMBAULT PLAY
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VIDEO: INTERVIEW WITH MS2 STEVE SWANSON PLAY
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VIDEO: INFORMAL NEWS CONFERENCE AT RUNWAY PLAY
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