A minor problem with an outpost solar wing forced veteran shuttle commander Jim Wetherbee to fly in formation with the station about an hour longer than expected. But the former military test pilot still managed to execute a flawless rendezvous.

"It was indeed an outstanding and stellar job," European Space Agency astronaut Gerhard Thiele told the shuttle commander from NASA's Mission Control Center in Houston, Texas. "Our kudos to the entire crew of Discovery, and welcome to Yuri, Susan and Jim in their new home."

In training now for four years, Usachev, Helms and Voss appeared ecstatic as they floated one-by-one into the station's spacious U.S. Destiny laboratory, a bus-sized research facility delivered by a visiting shuttle crew last month.

Usachev, 43, turned somersaults inside the lab and peered out of its 20-inch porthole, which is the finest optical quality window ever built for a spacecraft.

Helms, also 43, hugged station flight engineer Sergei Krikalev and Russian colleague Yuri Gidzenko as a smiling Shepherd watched on.

Voss, 52, shot videotape of the joined shuttle-station crew, which also includes Discovery pilot Jim Kelly and NASA mission specialists Paul Richards and Andy Thomas.

The decidedly informal hatch-opening ceremony signaled the start of a lengthy tour of duty for Usachev, Helms and Voss, who will spend the next four months outfitting the Destiny lab and overseeing further construction work at the outpost.

It also set the stage for the first of two spacewalks that will be carried out during Discovery's planned eight-day stay at the station.

Voss and Helms will venture outside the station at 11:47 p.m. today (04:47 GMT Sunday). They aim to prepare the outpost for the scheduled mid-April delivery of a Canadian-built robot arm. The crane-like device must be put in place before construction can continue at the complex.

Richards and Thomas will set out on a second spacewalk at 11:47 p.m. EST Tuesday (04:47 GMT Wednesday). That six-hour excursion will involve mounting a stowage platform and spare cooling system equipment outside the Destiny lab.

Launched last Thursday from Kennedy Space Center, Discovery docked at the station as the two craft soared some 235 miles (376 kilometers) above the Atlantic Ocean southeast of NASA's coastal Florida spaceport.

The high-flying hook-up took place at 1:38 a.m. EST (06:38 GMT), or about an hour later than planned.

A balky latch on one of the station's American solar wings forced the shuttle crew to hover 400 feet (121 meters) in front of the outpost until the glitch could be fixed.

The massive gold-and-blue arrays -- which have a wingspan of 240 feet (73 meters) -- glittered against pitch-black deep space in sequential still video images beamed back by the shuttle during its rendezvous with the station.

White clouds and blue oceans served as a backdrop for shots sent back from outpost cameras as the stubby-winged shuttle made its initial approach from below and behind the station.

Ground controllers lost direct contact with the shuttle as it linked up with the station, but Shepherd was able to pass along messages from Mission Control.

NASA flight director John Shannon said the lapse in communications caused "a little bit of excitement." The glitch, however, was fixed in about a half-hour as the combined crews turned their attention to a four-day changing of the guard at the station.

The staged transition is designed to give Shepherd as much time as possible to brief Usachev while Helms and Voss wrap up duties aboard Discovery.

To that end, Usachev carted a custom-made seat-liner into a Russian Soyuz spacecraft that serves as a lifeboat at the station. He also made sure his Russian partial pressure launch-and-entry suit fit properly before moving into the station.

Gidzenko then floated over into Discovery, officially becoming part of its crew.

Voss and Helms will swap places with Krikalev and Shepherd on Sunday and Tuesday, respectively.

Discovery and the station will remain linked in space for the next week. The ten astronauts and cosmonauts aboard the two craft will spend much of that time unloading five tons of equipment and supplies from an Italian moving van now cradled in the shuttle's cargo bay.

With Shepherd and company aboard, Discovery is scheduled to depart the station about 11 p.m. EST March 17 (04:00 GMT March 18), leaving the new outpost crew behind.

NASA's 103rd shuttle flight is due to land here at KSC at 2 a.m. EST (07:00 GMT) March 20, or 140 days after Shepherd's crew launched from Baikonur Cosmodrome in Kazakhstan.