Moving into orbital sunrise over China, a Soyuz spacecraft carrying three departing space station astronauts undocked today at 4:52 p.m. EDT (2052 GMT), the first step in a three-hour 20-minute flight back to Earth. There are no technical problems of any significance and landing in Kazakhstan remains on target for 8:12 p.m. EDT (0012 GMT).

During a brief farewell ceremony earlier this afternoon, the departing crew - Expedition 8 commander Michael Foale, Soyuz pilot Alexander Kaleri and Dutch guest astronaut Andre Kuipers - thanked ground controllers and wished their successors luck for a productive six-month mission.

"Thank you very much for your support, for everything we have accomplished," Foale, speaking Russian, told flight controllers. "We are sorry to leave the station, but we're looking forward to seeing you and everyone's families. Thank you very much."

Kaleri was a bit more reflective, saying "everything has a start and everything comes to completion."

"At the beginning of our expedition, we had a lot to do and (now) we have handed over the ship to our next crew," he said. Turning to Expedition 9 commander Gennady Padalka and Michael Fincke, he added "I would like to wish you every success in your flight, I hope you will have a good flight, I hope everything is completed on time and that you hand over the station to the crew that comes after you in good condition."

Replied Padalka: "Expedition 9 is ready to take over and the station is in excellent condition."

A final hatch between the space station and the Soyuz was closed and sealed at 1:47 p.m., setting the stage for undocking.

Several weeks ago, Russian flight controllers noticed a slight leak in one of two helium systems aboard the Soyuz that are used to pressurize the spacecraft's propulsion system for the deorbit rocket firing. The Russians normally fire a small pyrotechnic device to connect the two helium systems for re-entry, but because of the leak, that will not be done today. The leak-free manifold has more than enough pressure for a normal rocket firing, Russian engineers say. Even if a problem in that system did develop, on-board software would automatically switch to the other system. And in a worst-case scenario, the Soyuz could complete re-entry using smaller maneuvering thrusters.

But no such problems are expected and the Soyuz should hit the discernible atmosphere at an altitude of 400,000 feet - entry interface - about a half hour after deorbit ignition. The second of two pilot parachutes will pull out the spacecraft's drogue chute, which will slow the Soyuz's descent from 514 mph to about 179 mph. The Soyuz's main parachute then will unfurl, slowing the craft's descent velocity to just 16 mph.

Six solid-fuel motors will fire an instant before touchdown, reducing the Soyuz impact velocity to just 3.4 mph. Russian recovery forces will be standing by to assist the returning space fliers and to fly them back to Moscow.

For Foale and Kaleri, the eighth crew to make a long-duration stay aboard the space station, touchdown will close out a marathon voyage lasting 194 days 18 hours and 34 minutes since blastoff Oct. 18. Kuipers, representing the European Space Agency, will wrap up an 11-day stay in space. He blasted off April 19 with Expedition 9 commander Gennady Padalka and NASA flight engineer Michael Fincke. Padalka and Fincke plan to remain aboard the outpost until October, when they will be replaced by yet another two-man crew.