
Astronaut Ross exits through the hatch of the space shuttle Endeavour (top), works on the umbilical cords that connect the International Space Station modules (middle) and takes photographs as Endeavour's robot arm lowers him back into the shuttle's payload bay Monday

JOHNSON SPACE CENTER, Houston (CNN) -- The International Space Station was powered up and drawing energy from the sun on Tuesday after astronauts connected its wiring during a daring, 7 1/2-hour spacewalk.

On Monday, astronauts Jerry Ross and Jim Newman worked all over the exterior of the seven-story structure docked to the space shuttle Endeavour. They connected 40 cables that carried electricity, data and computer commands through space station segments, first joined Sunday.

The astronauts took just four hours to complete the couplings, an operation that flight directors had expected to take five or six hours.

At one point during the spacewalk, Newman asked Ross "Hey, Jerry, what are you doing?"

"Oh, I'm up here just hangin' around, building a space station," Ross answered.

In the extra time they had available, Newman and Ross attached sockets that will receive footholds for future spacewalkers. One of the sockets got away from Ross, but it floated harmlessly away from the shuttle/station combination.

Ross and Newman also investigated a jammed antenna used to guide spacecraft docking at Zarya. Engineers are trying to assess what, if anything, the crew may do to deploy the antenna.

Power and data were sent through the newly connected cables in a test closely monitored by ground controllers in Houston and Moscow.

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The test indicated that the cables were working properly and that the Russian-built Zarya module and U.S.-built Unity were operating in concert, NASA said Tuesday.

"Yesterday we put the skeleton together," said lead flight director Bob Castle. "Today we hooked up the first parts of the nervous system."

More spacewalks ahead

Endeavour's crew was getting light duty Tuesday. The only work scheduled is a slight orbit change to take the station complex three miles higher, and preparation for the second of three spacewalks Wednesday.

Tasks to be completed during the next extra-vehicular jaunt include installation of handrails and more foot restraint sockets and the installation of communication system antennas.

On Thursday, Endeavour's six-member crew will enter the station for the first time, opening the half-dozen hatches that will lead the crew through Unity and into Zarya.

The crew will begin to move in supplies and tools to be left for future crews. The first astronauts are scheduled to begin living on the space station in early 2000, after a Russian command module with living quarters is in place.

More than 100 space station components will eventually be assembled in orbit in one of the most ambitious engineering feats ever.

Sixteen nations are involved in the project, whose cost has been estimated at between $40 billion and $60 billion. Assembly will require six years and more than 40 manned space missions.

Reuters contributed to this report.