With their flawless docking behind them, Discovery's astronauts went on a spacewalk late tonight to spruce up the outside of the new international space station.

Tamara Jernigan and Daniel Barry floated out of the space shuttle around 11 p.m. The seven-story-plus station loomed above them, jutting straight out of Discovery's cargo bay.

"Unbelievable!" Jernigan said as she unlocked the hatch.

Among their duties during the six-hour outing: attaching a pair of 5-foot cranes to the exterior of the station, hanging out three bags of tools for future spacewalkers, installing a glare-reducing shroud over a docking target and covering an exposed pin.

The spacewalk was expected to last into the wee hours of Sunday.

No one was there to greet the seven shuttle astronauts when they arrived early today -- the first residents don't move in until March. So Mission Control extended an ultralong-distance welcome.

"It's been six months since anyone came to visit," Mission Control radioed up. "Welcome aboard."

"The whole station looks beautiful, and we're happy to be visiting," replied Barry.

It was the first of dozens of shuttle dockings expected for the space station, launched in two pieces late last year. Mission Control was delighted with the way everything went.

"You've made the first docking with space station look effortless, and you've set the standard for all those who follow," Mission Control told commander Kent Rominger, a Navy pilot who guided Discovery in.

The first order of business involved opening the outermost hatch of the space station and ducking a few feet inside to take air samples and do a little rearranging. The hatch was then closed; it won't be opened again until Sunday night, when the crew ventures all the way in.

NASA wanted the doors between the two spacecraft sealed in case there was an emergency during tonight's spacewalk.

Even though the plan called for Jernigan and Barry to attach themselves with double safety lines to the spacecraft at all times, and even though their spacesuits had jet packs, neither the National Aeronautics and Space Administration nor Rominger was taking any chances.

Rominger said before the flight that if one of the spacewalkers got loose and floated away, he'd ditch the station and chase after the astronaut.

Jernigan was a little anxious, but not because of any fear of snapped tethers.

During her last shuttle flight in 1996, a loose screw caused the hatch to jam, and her spacewalk was canceled. Workers at Kennedy Space Center promised her it wouldn't happen again, and it didn't.

Discovery will remain docked to the 77-foot, 70,000-pound space station until Thursday night. Between now and then, the astronauts will lug nearly 4,000 pounds of gear into the station for future crews to use as they live and work on the $50 billion station during its five-year assembly period.

Many of the supplies are packed into 123 cargo-transfer bags that look like suitcases. Thirty-seven of them will be unpacked and their contents stowed. The remaining 86 will be left aboard the station to be opened later.

CAPTION: Space shuttle Discovery astronauts Daniel Barry and Tamara Jernigan unpack their cameras before their cosmic construction work.