Shuttle prepares for flight home

The crews of Alpha and Discovery say their farewells on Monday.

(CNN) -- The crew of space shuttle Discovery said goodbye to space station Alpha on Monday, undocked, then paused to launch a small research satellite before buttoning up the shuttle for Wednesday's landing at Kennedy Space Center.

Discovery undocked from international space station Alpha at 10:52 a.m. EDT, completing a mission to deliver a new space station crew and to add equipment and experiments to Alpha.

Before the hatches connecting the two spacecraft were closed at 8:30 a.m. EDT, the crews of the two spacecraft gathered for a final farewell.

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"Yury, Jim, Susan, I know it's a tough day. I know it's hard to say good-bye," new Alpha commander Frank Culbertson told the departing Alpha crewmembers: Russian commander Yury Usachev and U.S. engineers Jim Voss and Susan Helms.

"But we really, really are proud of all you've done. We will do our best to keep up the good tradition you have started and to maintain just as high a standard of excellence if we can," he said.

Usachev, Voss and Helms spent five months on Alpha.

Culbertson, the former program manager of the shuttle-Mir program, showed off two plaques that had flown on the Russian Mir space station. He said he brought them to Alpha to tie the two stations together.

Heading home: Former Alpha crewmembers Yury Usachev, left, Jim Voss and Susan Helms

Culbertson will live on Alpha until December. He'll share duties on the station with cosmonauts Vladimir Dezhurov and Mikhail Tyurin. Among their first chores -- preparing for the arrival of a Russian Progress supply ship scheduled for launch from Kazahkstan early Tuesday.

In addition to dropping off the new Alpha crew, Discovery delivered equipment and supplies to the station in the Italian-built Leonardo Multi-Purpose Logistics Module. The module was reloaded with completed experiments form the station, personal items belonging to the returning Alpha crew, used equipment, packing foam and trash.

Also during the mission, a pair of Discovery astronauts went on two spacewalks to attach experiments, a spare ammonia container and cables to the outside of Alpha.

Simplesat

The last item on the shuttle's to-do list before heading back to the ground was deployment of a small science satellite called Simplesat. The satellite was ejected from the rear of the shuttle's cargo bay Monday afternoon.

Simplesat is about 2 feet long and 1-and-a-half-feet in diameter. It will be used to test whether off-the-shelf commercial technology can be used to build inexpensive satellites, according to Dave Skillman, the project's principal investigator.

The satellite was designed and built by one person with the help of some volunteers. The total cost of the project, according to Skillman, was $200,000.

Discovery is scheduled to land at Kennedy Space Center on Wednesday at 12:48 p.m. EDT.