posted 03-11-2009 08:25 AM               

Space shuttle Discovery stands poised on Pad 39A at the Kennedy Space Center in Florida to launch the STS-119 mission tonight at 9:20:14 p.m. EDT (0120 GMT).

STS-119 commander Lee Archambault will lead a crew of seven, along with pilot Tony Antonelli, and mission specialists Joe Acaba, John Phillips, Steve Swanson, Ricky Arnold, and Japan Aerospace Exploration Agency (JAXA) astronaut Koichi Wakata to the International Space Station (ISS).

Discovery will deliver the S6 truss segment and install the final set of power generating solar arrays to the ISS. The S6 truss will complete the backbone of the station and provide one-fourth of the total power needed to support a crew of six.

Photo credit: Bill Ingalls/NASA

Do you have comments and/or questions about the STS-119 mission? Post to our mission viewing and commentary thread.

posted 03-11-2009 08:39 AM               

The countdown resumed at 4:55 a.m. EDT Wednesday morning after a planned 13 hour and 7 minute hold at T-11 hours. There continues to be no technical issues standing in the way of tonight's liftoff.

posted 03-11-2009 11:07 AM               

Managers met at 11:15 a.m. EDT and gave a "go" to fuel Discovery's external tank with cryogenic liquid hydrogen and liquid oxygen, which began at 11:56.a.m.

posted 03-11-2009 01:23 PM               

A hydrogen leak detected in the ground umbilical carrier plate (GUCP) connecting Discovery's external tank to the pad has caused NASA to halt hydrogen fueling as they investigate the cause.

posted 03-11-2009 01:37 PM               

Tonight's planned launch of STS-119 was officially scrubbed at 2:37 p.m. EDT due to what a NASA spokesman described as a "slight" hydrogen leak in the gaseous hydrogen line running from the ground umbilical carrier plate (GUCP) that connects space shuttle Discovery's external tank to the pad.

Preparations are underway to begin detanking.

posted 03-11-2009 02:27 PM               

The Mission Management Team will meet at 5:00 p.m. EDT this evening to assess today's scrub and decide on the path forward.

According to Steve Roy with NASA's Marshall Space Flight Center, the leak is believed to have been in the External Tank Gaseous Hydrogen Vent Arm System, the 48-foot-long arm at the pad's 167-foot level that allows mating of the external tank umbilicals as well as contingency access to the intertank compartment.

The umbilical vent line provides continuous venting of the external tank during and after loading of the liquid hydrogen, but the leak was preventing the tank from being pressurized.

posted 03-11-2009 03:12 PM               

These images, captured off a Kennedy Space Center internal video feed, show the area of concern, the gaseous vent line and its connection point to the external tank, the ground umbilical carrier plate.

Second image courtesy Spaceflight Now

posted 03-11-2009 05:41 PM               

Mission managers have reset the launch of space shuttle Discovery on mission STS-119 to no earlier than Sunday, March 15 at 7:43:38 p.m. EDT (2343 GMT).

During a media briefing, launch director Mike Leinbach explained what happened that led to the decision to scrub Wednesday's attempt.

We got into our external tank loading on-time at five minutes to twelve this afternoon and everything was going fine...

When we were about 98 percent full on hydrogen, we [got] into a sequence from fast fill, where we're really pumping the fuel into the tank at a high rate, to a rate that we call 'topping'. The rate slows down and in conjunction with that slowing down of the filling, we opened the vent valve on the side of the external tank. It is that arm that connects to the side of the tank that falls away at T-0.

When we opened that vent valve, that was when we noticed the hydrogen leak on the ground side. Part of our standard procedure when we get a leak there -- and we've had leaks in this area before -- we cycle that valve and in the past, in the couple of the occasions that I remember personally, when you cycle that valve the leak goes away. Usually, it's a transient contamination issue or maybe a little bit of ice build up but nevertheless, in the past, when we cycle that valve, the leak stopped.

This time, it didn't.

We know we have some sort of hardware compromise out there. We cycled that valve on the order of eight or nine times and it never cleared up. We're sure we have some hardware issues out there. Until we actually get out there and inspect it, we're not exactly sure where in the system the hardware failure is, but I can tell you it is 99.9 percent sure it on the ground side, not the flight side.

We saw no hydrogen indications inside the intertank of the external tank, which is the area between the [liquid oxygen] and the hydrogen tanks. No issues there; it was purely an external leak at the connection there.

Due to scheduling constraints associated with the launch of the next space station crew on-board a Russian Soyuz scheduled for March 26, the latest Discovery can launch before slipping until April is Tuesday, March 17.

With each passing day however, the STS-119 mission is compressed such that a launch on Sunday, March 15 would result in a shortened 13-day flight with three spacewalks -- one less than originally planned. A launch on Monday or Tuesday would limit the mission even further to just nine or ten days, with the expectation of just one spacewalk to install the S6 truss.

The tightened schedule is preferred over a slip to April, as the alternative would have a greater impact on future shuttle flights, as well as the space station's ability to transition from a three to six-member crew.

Mission managers won't know until Friday at earliest if they can launch on Sunday.

posted 03-12-2009 03:26 PM               

Mission managers canceled their scheduled meeting today, to instead press ahead for a Sunday launch of space shuttle Discovery.

Based on the work done by engineers over the last day, NASA believes they now have a "sufficient understanding" of Wednesday's hydrogen leak to proceed with the launch of STS-119 at 7:43 p.m. EDT on Sunday.

posted 03-12-2009 05:56 PM               

NASA engineers will replace on Friday a seven inch quick disconnect on the hydrogen vent line to the ground umbilical carrier plate (GUCP) leading into space shuttle Discovery's external tank. The valve will then be retested and retorqued, before undergoing leak checks.

posted 03-13-2009 10:53 AM               

Engineers will spend Friday replacing metal seals as part of a "solid plan" to resolve a hydrogen leak so that Discovery can launch Sunday, managers said today.

"We're going to replace these components and get into a launch attempt Sunday," said launch director Mike Leinbach. "If it doesn't leak, we're going to fly. If it does leak again, then we'll stand down and go look at it again."

Part of the vent line connecting Discovery's external tank with the pad, the seals are located inside a quick disconnect interface (see photo and diagram below) that links the vehicle with the launch support structure through which hydrogen gas flows and is siphoned safely away from the pad.

In the past, replacement of the seals required a 30-hour period to torque and then re-torque after the seals have compressed to ensure a proper seating. To make a launch Sunday, engineers will rely on lessons learned from other applications, as well as on-going tests this afternoon, where data has suggested that the compression between seals occurs quickly, allowing a shorter time between when they are tightened.

As a "smoking gun" has yet to be found as the cause of the hydrogen leak that led to Wednesday's scrub, mission managers are hoping that replacing the seals will resolve the issue.

"The proof of the pudding will be when we get into external tank loading, and really once the tank gets pretty full when we get into that topping scenario just like we did on Wednesday," said Leinbach during a media briefing. "The gas we are venting out [then] is really cold as opposed to relatively warm, so it is going to be that thermal effect on the seal -- if the seal is the problem -- the thermal effect at that location is what we're going to be looking for."

Replacement of the seals is expected to be completed by Friday evening, with the reconnection of the vent line scheduled for tonight. Early Saturday, engineers will conduct a leak check, which if successful, will allow engineers to press ahead with preparations for a launch on Sunday.

Mission managers are planning to resume the launch countdown at T-11 hours at 3:18 a.m. EDT Sunday morning. The forecast calls for an 80% chance of favorable weather conditions.

Exploded view of the 7-inch quick disconnect with its internal seals depicted. Click to enlarge.

posted 03-14-2009 02:32 PM               

Mission managers, led by team chair Mike Moses, met on Saturday afternoon and agreed that there were no significant issues being worked that would prevent space shuttle Discovery from proceeding with a 7:43:46 p.m. EDT launch on Sunday.

"We're good to go tomorrow," said Moses. "We're looking forward to getting the count back running."

Technicians working at Pad 39A were finishing installation of the replaced vent line quick disconnect and its associated seals with the ground umbilical carrier plate (GUCP) that routes gaseous hydrogen away from Discovery's external tank and the pad.

A misalignment issue earlier today required the installation of guide pins to reinstall the quick disconnect, which resulted in a several hour delay. Managers were confident however, that the time they lost would not affect their ability to pick up the countdown at 3:18 a.m. EDT Sunday morning.

"We're three or four hours down on the time line, but we think we can make that up tonight and support the launch tomorrow," said launch director Mike Leinbach.

The "smoking gun" that led to Wednesday's hydrogen leak has yet to be identified, though engineers are narrowing in on what they believe might be the culprit.

"There was some evidence of the flight seal on the external tank side of the disconnect with a slight roll to it. I'm not sure that was the cause. There was a little bit of discoloration on one of the surfaces inside the quick disconnect. I'm not sure that is particularly related. It's probably the result of hydrogen leaking through that area. So no obvious smoking gun," explained Leinbach.

"While we like to have a smoking gun, good root cause, right now we don't have that," he added.

Final re-torquing of the replacement seals is expected to take place at 6:00 p.m., followed by the pad's rotating service structure being moved away from the vehicle at 8:30 p.m. Technicians will begin installation of the ordnance systems by midnight and tanking will begin at 10:18 a.m. on Sunday morning.

posted 03-14-2009 10:32 PM               

The rotating service structure that provided access for technicians to install the STS-119 payloads and protected the vehicle while it was on the pad was rolled back Saturday evening beginning around 8:30 p.m. EDT to reveal space shuttle Discovery.

Click on the photographs to enlarge.

posted 03-15-2009 09:24 AM               

As expected, the countdown to launch space shuttle Discovery began at the T-11 hour mark at 3:18 a.m. EDT Sunday morning.

Mission managers gave the go ahead to start loading cryogenic liquid oxygen and liquid hydrogen into Discovery's external fuel tank at 10:20 a.m.

Topping of the liquid hydrogen tank, which is when Wednesday's launch attempt developed a leak that led to a scrub, is expected to begin around 12:35 p.m.

posted 03-15-2009 10:22 AM               

When Discovery lifts off Pad 39A at 7:43:46 p.m. EDT, it will be lofted skyward by the 100th set of reusable solid rocket motors (RSRM) to fly since the loss of space shuttle Challenger in 1986.

The boosters, built by Alliant Techsystems (ATK), have a history unto themselves as they were built from segments that flew on 71 prior shuttle missions, including:

• STS-1, the first shuttle mission (right uppermost cylinder)
  
• STS-5, the first operational mission (left uppermost cylinder)
  
• STS-41D, the first flight of Discovery (right cylinder)
  
• STS-31, Hubble Space Telescope deploy (right aft dome)
  
• STS-61, first Hubble Space Telescope repair mission (right cylinder)
  
• STS-88, first shuttle to the International Space Station (left cylinder)
  
• STS-95, John Glenn's shuttle flight (left and right cylinders)
  
• STS-114, return to flight after Columbia (left and right cylinders)

posted 03-15-2009 11:07 AM               

A bat has been spotted clinging to the backside of Discovery's external tank, about a quarter to a third of the way from the bottom.

Mission managers expect the bat will fly away once the tank gets cold enough after being filled with cryogenic liquid hydrogen and liquid oxygen, now underway.

"If it doesn't," says NASA spokesman Mike Currie, "the bat is not expected to be a debris problem."

posted 03-15-2009 11:38 AM               

Fueling of Discovery's external tank with liquid hydrogen has surpassed the point when a gaseous hydrogen leak was detected during Wednesday's launch attempt.

The earlier leak, which resulted in manager's scrubbing the launch, was addressed by engineers by replacing a vent line's quick disconnect and its associated seals that ran hydrogen gas away from the tank through the ground umbilical carrier plate (GUCP).

"There's nothing observable coming from the location of that quick disconnect," said NASA spokesman George Diller.

posted 03-15-2009 12:23 PM               

Fueling of Discovery's external tank with cryogenic liquid hydrogen and liquid oxygen was completed at 1:21 p.m. EDT after 3 hours and 1 minute. The tanking entered a stable replenish mode as the countdown paused for a planned two hour and 30 minute hold at the T-3 hour mark.

posted 03-15-2009 03:44 PM               

The seven-person STS-119 crew, including JAXA space station flight engineer Koichi Wakata, departed their crew quarters and boarded the AstroVan for a ride to Pad 39A, where they are now seated inside space shuttle Discovery for tonight's 7:43:46 p.m. EDT launch.

Commander Lee Archambault and pilot Tony Antonelli are seated in the front seats of Discovery's flight deck, surrounded by the instrument panels and windows needed to control the orbiter. Mission specialist Steve Swanson will serve as flight engineer during ascent, so he is seated behind and between Archambault and Antonelli. Educator astronaut Joe Acaba is in a seat behind Antonelli where he, too, can help out during launch.

On the lower deck, Ricky Arnold, also a former teacher, is closest to the hatch. John Phillips, who is returning to the ISS after having lived there during Expedition 11, is in the center seat and Wakata is in the right-most seat. Sandy Magnus will sit in his place during landing, after Wakata transfers to the Expedition 18 crew.

posted 03-15-2009 05:06 PM               

The hatch through which the STS-119 crew boarded space shuttle Discovery has now been closed in preparation for tonight's 7:43:46 p.m. EDT launch.

The forecast for has been upgraded to a 100% chance of favorable weather.

Updates will be less frequent as we move into position to photograph the launch. collectSPACE will be capturing Discovery from atop the 525-foot tall Vehicle Assembly Building, where Discovery was mated with its solid rocket boosters and external tank before being rolled out to the launch pad.

posted 03-15-2009 07:44 PM               

Space shuttle Discovery made dusk into dawn as it lifted off with the STS-119 crew and the last set of power-providing solar wings for the International Space Station on Sunday at 7:43:44:074 p.m. EDT from Pad 39A at the Kennedy Space Center in Florida.

The STS-119 mission is carrying the space station's fourth and final set of solar array wings -- the last of the U.S.-built major components -- completing the station's truss, or backbone. The 13-day flight will feature three spacewalks to help install the S6 truss segment to the starboard, or right, side of the station and deploy its arrays. The flight will also replace a failed unit for a system that converts urine to potable water.

Discovery's launch was postponed from Wednesday, March 11, after a gaseous hydrogen leak was detected during fueling. No leaks were reported during Sunday's tanking after technicians rebuilt and replaced seals associated with a hydrogen vent line.

"You had a little bit of a wait, but it'll make the payoff that much sweeter," NASA's shuttle launch director Mike Leinbach told Discovery commander Lee Archambault just before launch. "Good luck and Godspeed."

"Thanks for the work Mike, we'll see you in a couple of weeks, take care and let's go ahead and fire up the sound of freedom," Archambault replied.

Archambault is leading a crew of six to space, including pilot Tony Antonelli and mission specialists Joseph Acaba, Steve Swanson, Richard Arnold, John Phillips, and Japan Aerospace Exploration Agency (JAXA) astronaut Koichi Wakata.

Wakata will replace space station flight engineer Sandy Magnus, who has been on the station for more than four months.

Former science teachers, Acaba and Arnold will to step outside the space station to conduct spacewalks with Swanson.

posted 03-16-2009 10:36 AM               

Following a picture perfect launch from the Kennedy Space Center Monday evening, space shuttle Discovery is racing toward the International Space Station for its planned rendezvous and docking at 4:13 p.m. CDT on Tuesday.

A few hours after liftoff, mission control informed the STS-119 astronauts that their first look at ascent imagery showed no debris items of concern. The imagery review process will continue over the next several days.

The crew began their first full day in space at 9:13 a.m., known as Flight Day 2.

"Good morning Discovery, and especially to Tony," mission control radioed pilot Tony Antonelli, a first time flier, after playing "Free Bird" by Lynyrd Skynyrd as the crew's wake-up song.

posted 03-16-2009 12:36 PM               

As space shuttle Discovery continues on its path to rendezvous and dock with the International Space Station on Tuesday, a piece of a defunct Russian satellite may force the outpost to maneuver out of the way.

A remnant from the Soviet-era navigation satellite Cosmos 1275 is expected to come within a half-mile of the space station at 2:14 a.m. CDT on Tuesday.

If NASA decides a move is in order, then the station crew will executive the minor maneuver at 8:54 p.m. CDT tonight. Flight controllers are still assessing the pass.

Meanwhile aboard Discovery, the STS-119 crew is preparing to use the shuttle's robotic arm to inspect their heat shield for any potential damage that debris may have caused during ascent.

posted 03-16-2009 10:18 PM               

As part of their flight day video highlights, STS-119 commander Lee Archambault is shown presenting pilot and first-time flier Tony Antonelli his Naval astronaut wings.

"I was real happy to be able to do this," Archambault narrated as the video was downlinked to the ground, "I exchanged name tags for Tony. I took his Naval Aviator wings and replaced them with Naval Astronaut Aviator wings."

"I was really honored to be able to do that little presentation for Tony."

posted 03-17-2009 09:28 AM               

"Erin go Bragh, Discovery, and happy St. Patrick's Day," capcom Janice Voss radioed to space shuttle Discovery's crew as they began their morning at 8:44 a.m. CDT.

The STS-119 crew awoke to "Radio Exercise," a song that Japanese children exercise to, performed by the Tokyo Broadcast Children's Choir. Japan Aerospace Exploration Agency (JAXA) astronaut Koichi Wakata will join the International Space Station crew this evening, following Discovery's planned docking to the station at 4:12:46 p.m. CDT.

posted 03-17-2009 01:28 PM               

As Discovery continues its approach to the space station for a planned docking at 4:12 p.m. CDT, engineers on the ground have determined the status of the small bat that stubbornly clung to the shuttle's external tank (ET) prior to, and -- as it turns out -- through launch.

A shuttle engineering memo, obtained by collectSPACE, notes: "He did change the direction he was pointing from time to time throughout countdown but ultimately never flew away. IR imagery shows he was alive and not frozen like many would think. The surface of the ET foam is actually generally between 60-80 degrees F on a day like [Sunday]."

"Lift off imagery analysis confirmed that he held on until at least the vehicle cleared to tower before we lost sight of him."

"And thus is the legend of the STS-119 Bat-ronaut..."

posted 03-17-2009 03:39 PM               

Discovery, at a separation of about 600 feet below the International Space Station, performed a nine-minute back flip, known as the Rendezvous Pitch Maneuver, to enable the station's crew members to photograph the orbiter's heat shield for later analysis by engineers on the ground.

Discovery is now moving from underneath to in front of the ISS and will slowly close the gap between them. Docking is expected at 4:12:46 p.m. CDT.

posted 03-17-2009 04:22 PM               

Space shuttle Discovery docked with the International Space Station at 4:19:53 p.m. CDT while the two vehicles were flying over Lake Wells, western Australia.

"Welcome to the space station, Discovery. We're glad you're here," radioed ISS Expedition 18 commander Mike Fincke.

"We're glad we're here also," replied STS-119 commander Lee Archambault.

Hatches between Discovery and the station will be opened at around 6:00 p.m., followed by a welcome ceremony.

At about 6:30 p.m., JAXA astronaut Koichi Wakata will become a member of the station's Expedition 18 crew and Sandy Magnus will become a member of Discovery's crew. Magnus will have been a space station crew member for 121 days.

posted 03-17-2009 07:42 PM               

Hatches between space shuttle Discovery and the International Space Station were opened at 6:09 p.m. CDT. Passing underneath a St. Patrick's Day shamrock as they floated into the Harmony module, the seven STS-119 astronauts were met by the three-member Expedition 18 crew.

"We've been waiting for you guys for a while," said Expedition 18 commander Mike Fincke to the shuttle crew. "We understand you have a couple of really important things for us..."

"First and foremost, Koichi-san, first long-duration Japanese guy in space ever. Welcome aboard!" said Fincke to JAXA astronaut Koichi Wakata.

"We also understand you have a (solar power) truss out there -- more power to us -- got some spacewalks lined up, we're excited for that.

"And also, it's always proper to recognize a former space station crew member. John, welcome back. It's gotten a lot bigger since we both first flew on here," said Fincke.

"It's great to be back," said John Phillips, who was last aboard the station during Expedition 11 in 2005.

"So welcome, Lee, welcome to your entire crew, we are dang glad to see you!" Fincke concluded.

"It's an honor to be here again, the second time for myself and Swanny and John," replied STS-119 commander Lee Archambault. "We're really delighted to join you, Sandy, Yuri. We've got a lot of work to do, we're looking forward to it... but this is a very special moment. So thanks for having us aboard."

"So let's get to work!" Fincke said.

posted 03-18-2009 08:10 AM               

At 9:00 p.m. CDT Tuesday evening, STS-119 mission specialist Koichi Wakata became the first Japanese long duration space station crew member, joining ISS Expedition 18.

His transfer was officially marked by the installation of a specially-fitted seat liner inside the Soyuz spacecraft.

At the same time, ISS flight engineer Sandy Magnus ended her 121 days and 10 minutes as a station crew member, swapping places with Wakata.

Discovery's crew ended their day by narrating their flight day highlights, featuring footage of their rendezvous, docking and entrance into the space station.

Just before they went to bed, capcom Greg "Box" Johnson shared the first findings regarding the health of the orbiter's heat shield.

"A quick look at the RPM [rendezvous pitch maneuver, or backflip] imagery shows there is a tile on the left inboard elevon that has some substrate exposed," radioed Johnson. "That is the only item that the team is scrutinizing at this point. There is no decision regarding any focused inspection but we will continue to analyze that spot overnight."

posted 03-18-2009 08:16 AM               

The STS-119 crew aboard the space shuttle Discovery woke up at 7:43 a.m. CDT to the song "I Walk the Line" by Johnny Cash, played for lead spacewalker Steve Swanson.

Robotics will dominate today's activities as the station's and shuttle's robotic arms are used to carefully lift the S6 truss segment from Discovery's bay to prepare it for Thursday's installation.

The truss is the last U.S.-built major component to be added to the space station.

posted 03-18-2009 10:59 AM               

Sandy Magnus and John Phillips grappled the S6 truss segment inside Discovery's payload bay at 10:45 a.m. CDT using the station's robotic arm.

The two former flight engineers will next use the Canadarm2 to unberth the 31,127 pound, 45.4 foot long truss. Once clear of Discovery's bay, the segment will be handed off to the shuttle robotic arm, so that the station arm can be repositioned for the truss' installation.

posted 03-18-2009 11:34 AM               

The S6 truss has been successfully unberthed from Discovery's payload bay using the space station's robotic arm.

The truss will next be handed off to the shuttle robotic arm, freeing the station arm to be repositioned so that it can then retake the segment for installation at the end of the station's backbone.

posted 03-18-2009 12:47 PM               

STS-119 pilot Tony Antonelli and educator astronaut Joe Acaba grappled the S6 truss using the shuttle's robotic arm at 12:39 p.m. CDT while it was being held outside Discovery's payload bay by the station's robotic arm controlled by STS-119 mission specialists Sandy Magnus and John Phillips.

A few minutes later, the station arm's grasp was released, leaving the shuttle arm holding the truss.

posted 03-18-2009 05:30 PM               

After moving approximately 100 feet down the station's backbone, the Canadarm2 again took hold of the S6 truss at 5:10 p.m. CDT.

The truss will remain at the end of the arm until tomorrow, when it will be attached to the S5 truss with the assistance of STS-119 spacewalkers Steve Swanson and Ricky Arnold.

posted 03-18-2009 06:01 PM               

As the S6 truss was being moved between shuttle and station arms, members of the STS-119 and Expedition 18 crews took a break to answer questions posed by students through Channel One News.

Station and Discovery commanders Mike Fincke and Lee Archambault, as well as educator astronauts Ricky Arnold and Joe Acaba participated in the event.

posted 03-18-2009 06:41 PM               

"After fully analyzing the data, we have determined the focused inspection is not required," capcom Greg "Box" Johnson informed STS-119 commander Lee Archambault, "so, we're going to modify the timeline via the pre-flight agreement for no focused inspection."

Of possible concern was a 0.25 to 0.35 inch divot in a two-inch thick tile located on the shuttle's left inboard elevon.

"Margins are good for the RTV bond for that damaged tile and factor of safety is 1.8 or better. So we are ready to press with the pre-flight agreement," concluded Johnson.

"Gotcha loud and clear Box," relied Archambault. "Thank you very much. That's absolutely great news and we look forward to seeing the reworked timeline."

posted 03-19-2009 09:00 AM               

As the STS-119 crew ended their third full day in space (Flight Day 4), mission specialists Steve Swanson and Ricky Arnold "camped out" inside the the reduced air pressure atmosphere of the station's Quest airlock to prepare their bodies for their planned six and a half hour spacewalk on Thursday to install the S6 truss.

Meanwhile, their crewmates aboard Discovery shared highlights from the personal videos they captured over the last couple of days.

posted 03-19-2009 09:07 AM               

"Good morning Discovery, and a special good morning to you Joe," capcom Janice Voss radioed from Mission Control after waking the STS-119 crew at 7:13 a.m. CDT with the song "Que Bandera Bonita" by Jose Gonzalez.

"Thank you very much for that and I want to thank my family for helping to pick it out, and to the Puerto Rican community for all the support they've given me," mission specialist Joe Acaba replied. "We're ready for a busy day to get that truss attached today."

Today's top task, attaching the last segment of the station's truss, or backbone, will require use of both robotic and human arms.

The station's robotic arm, Canadarm2, will be used to move the S6 segment into position. Spacewalkers Steve Swanson and Ricky Arnold will then bolt the 31,000 pound truss into place and make the electrical and data connections to activate its power and cooling systems.

posted 03-19-2009 12:17 PM               

With the S6 truss segment at its pre-installation position 5 feet from the end of the S5 truss (having been moved there by John Phillips and Koichi Wakata using the station robotic arm), STS-119 spacewalkers Steve Swanson and Ricky Arnold are exiting the Quest airlock to begin their 6.5 hour excursion to complete the station's 310 foot truss, or backbone.

Lead spacewalker Swanson is wearing a spacesuit with red stripes. Arnold, making his first spacewalk, is wearing a suit with no stripes.

The spacewalk officially began at 12:16 p.m. CDT.

"Give us some more power and good job getting out the door," said Expedition 18 commander Mike Fincke as the two spacewalkers departed, referencing the power generating solar arrays to be deployed following the installation of the S6 truss.