The Soyuz TMA-2 space capsule (search) carrying American astronaut Edward Lu and Russian cosmonaut Yuri Malenchenko docked Monday with the international space station in a key step to replacing the station's three-man crew, space officials said.

The docking took place on schedule at 9:56 a.m. (1:56 a.m. EDT) about 250 miles high above Russian territory. The two crews greeted each other with hugs after the hatch was opened and Lu and Malenchenko entered the space station.

Lu and Malenchenko are replacing the trio of U.S. astronauts Kenneth Bowersox and Donald Pettit and Russian cosmonaut Nikolai Budarin, who were stuck on the station after the Columbia Shuttle disaster (search) on Feb. 1.

Lu's mother, Snowlily, was on hand for the docking at Mission Control outside Moscow. "I am just so happy and proud to see everything work out so well," she said.

The astronaut's mother, his brother, Rick, and his fiancee, Christine Romero, cheered as the vessels established the connection. Flight controllers also applauded.

"This is amazing ... It gives me a lot of relief to see that they're up there," Romero said. "Everyone is proud not just for what Ed is doing, but for NASA and the international space station and for the space program as a whole, especially after the Columbia."

Snowlily Lu said that space officials were setting up equipment for her to communicate with Edward from her home. "The first thing I'll say is congratulations. You've done a great job," she told reporters.

The Russian spacecraft blasted off Saturday morning from Russia's Baikonur cosmodrome in the steppes of Kazakhstan on its way to the $60 billion international space station.

Shortly after Monday's automated docking, the Russian spacecraft began the process of sealing to the space station. Then after 90 minutes of checks for any leaks, the hatch was opened and the crews greeted one another, said Rob Navias, spokesman for NASA. Lu and Malenchenko are bringing gifts to celebrate the birthdays of Pettit, who turned 48 on April 20, and Budarin who turns 50 on Tuesday, Russia's ITAR-Tass news agency reported.

But there won't be much time to celebrate: the crews have a lot of information to exchange. The trio on the international space station must give the newcomers a tour and explain safety procedures.

The American and Russian duo will give Bowersox, Pettit and Budarin a refresher course on how to operate the Soyuz capsule, which they will use to return to Earth on May 3.

The three returning crew members will be taking back an older Soyuz already docked to the station, while the one carrying Lu and Malenchenko will stay up there with them as an "emergency lifeboat" in case they need to quickly evacuate.

The trio's return on the Soyuz will mark the first time that U.S. astronauts have come home on a Russian space vessel. Originally they had planned to return on a U.S. shuttle but the Columbia disaster forced the grounding of the U.S. fleet.

The Russian Soyuz then became the only ship capable of carrying crews to and from the space outpost, giving it a vital role in keeping the station manned.

Lu and Malenchenko, who briefly visited the space station in 2000 before it was permanently occupied, are scheduled to remain onboard until October.