The crew of space shuttle Atlantis opened the first of 12 hatches leading into the 140-foot-long station a little early, entering the outermost vestibule and then the American module, Unity.
"Welcome aboard," Mission Control radioed up.
"It's great to be here," commander Terrence Wilcutt replied.
It was expected to take a few hours for the seven men to make their way through the complex. The pressure had to be equalized from one compartment to another before doors could be opened.
It was warm inside Unity â€“ 81 degrees, although the humidity was low. The commander and his crew seemed comfortable as they set up air ducts and consulted their checklists.
Earlier in the day, a pair of spacewalkers hooked up cables, installed a navigation tool and dislodged a jammed piece of equipment on the outside of the space station. Once that was accomplished, the crewmen turned their attention to the inside.
"Basically, it's a cabin we have that we're trying to get some furniture into and get it ready to move into," said mission operations director Milt Heflin.
The space station is almost twice the size it was the last time astronauts visited in May. Zvezda, the Russia-made control module, was added in late July. The crew is working fast, as Atlantis undocks in four days.