The $300 million S6 solar array truss segment has been bolted into place on the far right end of the space station's main power truss.

Astronauts John Phillips and Koichi Wakata, operating the space station's robot arm from a work station inside the Destiny laboratory module, carefully guided the 31,000-pound starboard 6, or S6, truss segment into contact with the S5 spacer segment at 2:17 p.m. EDT.

Spacewalker Richard Arnold used a power tool to drive an internal capture claw closed, pulling the two segments together. Four big corner bolts then were driven home to complete the physical attachment at 3:06 p.m. EDT.

Arnold and Steven Swanson then connected two electrical cables and a pair of data cables, struggling at times with several clamps. But just before 4 p.m., the cable connections were complete and flight controllers were told they could begin activation procedures.

"Houston, Discovery. It wasn't quite as smooth as we had hoped, but those guys did a great job and I'm very happy to say you have a go for S6 activation," astronaut Joseph Acaba radioed from inside the shuttle Discovery.

"Outstanding news," mission control replied. "Thanks for all the hard work on that. We'll put the activation in work right now."

Remaining work includes stowing a keel pin, removing launch locks, releasing a stowed radiator and deploying the canisters and blanket boxes that hold the folded solar arrays in place. If all goes well, the panels will be extended by remote control Friday.

Swanson and Arnold switched their spacesuits to internal battery power at 1:16 p.m. to officially begin today's planned six-and-a-half-hour spacewalk.

After arranging safety tethers, the spacewalkers headed to the far right end of the station's main power truss where the 45-foot-long S6 segment had been positioned by the lab's robot arm.

This is the 121st spacewalk devoted to station assembly and maintenance since construction began in 1998, the first of three planned for DIscovery's mission, the third for Swanson and the first for Arnold, a former school teacher making his first flight. Going into today's excursion total station EVA time stood at 755 hours and 56 minutes, or 31.5 days.

Mission managers continue to discuss possible flight plan changes to make sure experiment samples get back to Earth in good condition even if the shuttle Discovery's landing is held up by bad weather.

Planners initially considered shortening the mission one day to provide a bit of a cushion, but they now are considering delaying space station hatch closure to undocking day instead of the day before. That would give the experiment samples additional shelf life without having to shorten the flight. But no final decisions have been made.

Additional coverage for subscribers:
VIDEO: WEDNESDAY'S MISSION STATUS BRIEFING PLAY
VIDEO: PREVIEW ANIMATION OF S6 TRUSS UNBERTHING PLAY
VIDEO: NARRATED TOUR OF DISCOVERY'S PAYLOAD BAY PLAY

VIDEO: FLIGHT DAY 3 HIGHLIGHTS MOVIE PLAY
VIDEO: TUESDAY'S MISSION STATUS BRIEFING PLAY
VIDEO: SHUTTLE CREW WELCOMED ABOARD STATION PLAY
VIDEO: SPACE SHUTTLE DISCOVERY DOCKS TO SPACE STATION PLAY
VIDEO: SHUTTLE'S POINT OF VIEW DURING BACKFLIP PLAY
VIDEO: DISCOVERY PERFORMS 360-DEGREE BACKFLIP PLAY
VIDEO: PREVIEW ANIMATION OF RENDEZVOUS AND DOCKING PLAY

VIDEO: FLIGHT DAY 2 HIGHLIGHTS MOVIE PLAY
VIDEO: MONDAY'S MISSION STATUS BRIEFING PLAY
VIDEO: MONDAY'S MISSION MANAGEMENT TEAM UPDATE PLAY
VIDEO: PREVIEW ANIMATION OF HEAT SHIELD INSPECTIONS PLAY

VIDEO: FLIGHT DAY 1 HIGHLIGHTS MOVIE PLAY
VIDEO: THE FULL STS-119 LAUNCH EXPERIENCE PLAY
VIDEO: LAUNCH REPLAY: EXTERNAL TANK CAMERA PLAY
VIDEO: LAUNCH REPLAY: VAB ROOF PLAY
VIDEO: LAUNCH REPLAY: CAMERA CS-1 PLAY
VIDEO: LAUNCH REPLAY: CAMERA CS-2 PLAY
VIDEO: LAUNCH REPLAY: CAMERA CS-6 PLAY
VIDEO: LAUNCH REPLAY: FRONT CAMERA PLAY
VIDEO: LAUNCH REPLAY: BEACH TRACKER PLAY
VIDEO: LAUNCH REPLAY: PAD PERIMETER PLAY
VIDEO: LAUNCH REPLAY: PLAYALINDA BEACH PLAY
VIDEO: LAUNCH REPLAY: THE VIP VIEWING SITE PLAY
VIDEO: LAUNCH REPLAY: PRESS SITE PLAY
VIDEO: LAUNCH REPLAY: WEST TOWER PLAY
VIDEO: LAUNCH REPLAY: CAMERA 009 PLAY

VIDEO: SPACE SHUTTLE DISCOVERY BLASTS OFF PLAY
VIDEO: SHUTTLE'S CREW MODULE HATCH CLOSED FOR FLIGHT PLAY
VIDEO: MISSION SPECIALIST STEVE SWANSON BOARDS PLAY
VIDEO: PILOT TONY ANTONELLI BOARDS DISCOVERY PLAY
VIDEO: COMMANDER LEE ARCHAMBAULT BOARDS PLAY
VIDEO: CREW DEPARTS QUARTERS FOR LAUNCH PAD PLAY
VIDEO: ASTRONAUTS DON SPACESUITS FOR LAUNCH PLAY
VIDEO: TIME-LAPSE OF SUNRISE AT LAUNCH PAD 39A PLAY
VIDEO: TIME-LAPSE OF HYDROGEN ACCESS ARM RETRACTION PLAY
VIDEO: TIME-LAPSE OF SATURDAY NIGHT'S GANTRY ROLLBACK PLAY
VIDEO: SATURDAY'S PRE-LAUNCH NEWS CONFERENCE PLAY
VIDEO: FRIDAY'S SHUTTLE AND WEATHER UPDATE BRIEFING PLAY

VIDEO: POST-SCRUB NEWS CONFERENCE PLAY
VIDEO: DISCOVERY IN THE PREDAWN DARKESS PLAY | HI-DEF
VIDEO: WEDNESDAY'S ROLLBACK OF PAD GANTRY PLAY | HI-DEF
VIDEO: TIME-LAPSE OF PAD GANTRY ROLLING BACK PLAY
VIDEO: THE PRE-LAUNCH NEWS CONFERENCE PLAY
VIDEO: ASTRONAUTS ARRIVE IN FLORIDA FOR LAUNCH PLAY
VIDEO: POST-ARRIVAL COMMENTS FROM THE CREW PLAY | HI-DEF

VIDEO: FLIGHT READINESS REVIEW BRIEFING PLAY

VIDEO: SECOND LAUNCH POSTPONEMENT BRIEFING PLAY

VIDEO: NARRATED MISSION OVERVIEW MOVIE PLAY
VIDEO: MEET SHUTTLE DISCOVERY'S ASTRONAUTS PLAY
VIDEO: INTERVIEW WITH COMMANDER LEE ARCHAMBAULT PLAY
VIDEO: INTERVIEW WITH PILOT TONY ANTONELLI PLAY
VIDEO: INTERVIEW WITH MS1 JOE ACABA PLAY
VIDEO: INTERVIEW WITH MS2 STEVE SWANSON PLAY
VIDEO: INTERVIEW WITH MS3 RICKY ARNOLD PLAY
VIDEO: INTERVIEW WITH MS4 JOHN PHILLIPS PLAY
VIDEO: INTERVIEW WITH MS5 KOICHI WAKATA PLAY

VIDEO: NASA OFFICIALS ANNOUNCE LAUNCH DELAY PLAY
VIDEO: SPACE STATION'S VIBRATIONS DURING REBOOST PLAY

VIDEO: INFORMAL NEWS CONFERENCE AT RUNWAY PLAY
VIDEO: ASTRONAUTS ARRIVE FOR PRACTICE COUNTDOWN PLAY

VIDEO: DISCOVERY POSITIONED ATOP PAD 39A PLAY | HI-DEF
VIDEO: EARLY MORNING ROLLOUT FROM THE VAB PLAY | HI-DEF
VIDEO: TIME-LAPSE MOVIE OF DISCOVERY ARRIVING AT PAD 39A PLAY

VIDEO: DISCOVERY HOISTED FOR ATTACHMENT TO TANK PLAY | HI-DEF
VIDEO: CRANE ROTATES DISCOVERY VERTICALLY PLAY | HI-DEF
VIDEO: DISCOVERY MOVES TO ASSEMBLY BUILDING PLAY | HI-DEF
VIDEO: NOSE WHEEL LANDING GEAR RETRACTED PLAY | HI-DEF

VIDEO: TIME-LAPSE MOVIE OF DISCOVERY GOING VERTICAL PLAY
VIDEO: TIME-LAPSE MOVIE OF ASSEMBLY BUILDING CRANE WORK PLAY
VIDEO: TIME-LAPSE MOVIE OF DISCOVERY'S TRIP TO VAB PLAY
VIDEO: TIME-LAPSE MOVIE OF PAYLOAD'S MOVE PLAY

VIDEO: SHUTTLE AND STATION PROGRAM UPDATE PLAY
VIDEO: STS-119 MISSION OVERVIEW BRIEFING PLAY
VIDEO: PREVIEW BRIEFING ON MISSION'S SPACEWALKS PLAY
VIDEO: THE ASTRONAUTS' PRE-FLIGHT NEWS BRIEFING PLAY
MORE: STS-119 VIDEO COVERAGE
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