Mission Status Center

Flight Day 7 is winding down in orbit. Mission Control is working to replan Tuesday's spacewalk to accommodate the tasks not completed in today's EVA, including the fluid line connections to the new ammonia tank and retrieval of some space debris shields that will be brought back to Earth inside the Leonardo module.

Today marked the 142nd spacewalk devoted to station assembly and maintenance since construction began in 1998, the sixth so far this year and the second of three planned by the shuttle Discovery's crew. Total space station EVA assembly time now stands at 887 hours and nine minutes, or about 37 days.

A pair of experienced spacewalkers went outside the International Space Station overnight to remove a spent ammonia coolant tank and install a reservoir of fresh coolant for the outpost's network of thermal plumbing.

Lengthy struggles to get the 1,700-pound structure bolted down, however, put the astronauts well behind schedule and caused Mission Control to postpone hooking up the fluid lines to the new tank until a future EVA.

Astronauts Rick Mastracchio and Clay Anderson began today's spacewalk at 1:30 a.m. EDT, some 45 minutes early. Things were going smoothly until they tried to engage the four bolts that would attach the new tank to the Starboard 1 truss. They fought with getting the bolts lined up and torqued down for over 90 minutes before finally succeeding.

But the unexpected difficulty threw the spacewalk timeline off track, forcing flight controllers to defer the connection of the ammonia transfer lines and nitrogen pressurization umbilicals to the new tank. The astronauts did route a pair of electrical cables to establish power and data paths between the station and tank assembly.

The decision to delay mating the fluid lines was ordered because not enough time remained in the EVA to deal with any spacesuit contamination that could occur when plugging in the ammonia umbilicals.

This was the second of three excursions for the Discovery mission, with the final EVA planned for early Tuesday to stow the old ammonia tank in the shuttle's payload bay for return to Earth, plus complete some other chores and maintenance on the space station's exterior.

This was the fifth EVA in the careers of both astronauts. Rick Mastracchio has accumulated 32 hours, 6 minutes and Clay Anderson 32 hours, 4 minutes of spacewalking time on their previous three excursions in 2007 and the one on Friday morning.

EVA ENDS. Repressurization of the Quest airlock module began at 8:56 a.m. EDT, marking the official end of today's spacewalk by Rick Mastracchio and Clay Anderson. The EVA lasted 7 hours and 26 minutes.

This was the second of three spacewalks planned for Discovery's mission to the space station. The time elapsed for the two excursions now totals 13 hours and 53 minutes.

The final EVA is planned for Tuesday morning starting around 3:15 a.m. EDT to stow the old tank in the shuttle's bay.

The airlock hatch has been closed and locked. Standing by for repressurization.

The depleted ammonia tank removed from the Starboard 1 truss earlier today has been mated to the station's mobile transporter. The tank must be left in this temporary spot until the next spacewalk on Tuesday morning. In between EVAs, the station's arm relocates its operating base so that it can reach into the payload bay of shuttle Discovery for depositing the tank on the carrier pallet to ride back to Earth.

The spacewalkers are climbing into the airlock to finish this successful outting.

Passing the seven-hour mark of the spacewalk.

Tool inventories and glove checks are underway before the spacewalkers make their way toward the airlock.

The grapple fixture has been installed to the underside of the old ammonia tank by the spacewalkers. The station's arm can now maneuver the tank over the mobile transporter and dock the payload there.

The spacewalkers are working to attach a handling device on the old tank. This fixture will enable the tank to be anchored onto the station's mobile transporter for the next two days.

The station's arm has a firm grip on the old tank, which was held steady by the spacewalkers.

Six hours and counting into today's spacewalk. The spacewalkers are working to untie the old tank from the CETA cart for the station's robot arm to come pick up.

The spacewalkers are cleaning up their worksite around the new ammonia tank before moving onward with the remaining tasks in the EVA.

Mission Control reports a good data flow from both of the power connections. The new ammonia tank is structurally and electrically joined to the Starboard 1 truss.

The second of two power cables is hooked up to the tank now.

Astronauts Rick Mastracchio and Clay Anderson ran into problems bolting a 1,700-pound ammonia coolant tank into place on the space station's power truss early Sunday. Finally, after multiple attempts over an hour and a half, Anderson drove a recalcitrant bolt home to clear the problem.

Read our full story.

The tank's final bolting is being completed.

The astronauts are connecting a pair of electrical cables to the new tank.

Mission Control says that the astronauts will defer connecting the nitrogen and ammonia fluid lines during today's spacewalk because of the delays getting the tank installed. There's not enough time left in this EVA to deal with any contamination that could happen when plugging in the ammonia transfer umbilicals.

Also, the retrieval of some external debris shields stashed outside the station that the spacewalkers were supposed to bring back inside for stowing in the Leonardo module won't occur today after all.

The second bolt has been fully torqued down by Anderson.

With a "come on baby" and "git er done" from spacewalker Clay Anderson, he has successfully gotten this troublesome bolt fully tightened down. He'll move over to the next bolt while Rick Mastracchio continues to hold the other side of the tank.

Clay Anderson has this bolt partially engaged.

They've got one of these troublesome bolts lined up at last!

Now five hours into today's spacewalk.

An effort to start all over again with the installation hasn't succeeded eitehr.

The new plan calls for releasing the one good bolt and then try to reseat the tank onto the station.

The spacewalkers are going to move a foot platform to improve the work area.

Still no luck in getting the tank attached. Releasing the first of two bolts that was installed hasn't cleared the problem. At present, only one of the four bolts is engaged.

Mission Control is thinking that perhaps the first bolt wasn't installed properly, which could have the tank mispositioned.

Clay Anderson has gone back to airlock and gotten some more tools. They cannot get the remaining bolts inserted.

The crew is struggling to get all four bolts tightened.

The tank is being structurally mated to the station with four bolts.

The robot arm has let go of the new tank for the spacewalkers to manually dock.

The new tank is coming within range of the Starboard 1 truss for the spacewalkers to take the handoff from the station's arm.

The arm is swinging the 1,700-pound coolant tank toward its new home on the Starboard 1 truss.

The new tank has been brought within reach of the spacewalkers for them to remove the temporary anchoring fixture. This bar was attached to the underside during EVA No. 1 in order to mount the tank onto the station's mobile transporter. Later in this spacewalk, they will connect the bar to the old tank for the same function.

The space station's robotic arm, flown today by mission specialist Stephanie Wilson and pilot Jim Dutton, has picked up the new ammonia tank from the mobile transporter's payload accommodation holding fixture. The tank was launched aboard shuttle Discovery and got transferred over to the station during the first spacewalk on Friday morning.

While waiting for the station arm to retrieve the new ammonia tank, the spacewalkers are making their way to the Port 1 truss to install so-called radiator grapple fixture stowage beams. These will store some handles that would be needed in the future to replace one of the station's radiators.

The robot arm has released its grip on the 1,295-pound tank for the spacewalkers to strap onto the cart called CETA, or Crew Equipment Translation Aid. They are using six tethers to secure the tank on the cart.

The space station's robotic arm is manuevering the old tank toward the CETA cart on the rail tracks where it will be tied down for a couple of hours, freeing the arm to handle the new tank. Later in the spacewalk, the old tank will be installed on the station's mobile transporter where the new tank has been hanging out since EVA No. 1 on Friday morning.

Space shuttle pilot Jim Dutton is operating the space station's robotic arm along with mission specialist Stephanie Wilson during today's spacewalk. Dutton previews his work in this pre-flight interview:

"EVA 2 is really kind of shell game. We've got the new ammonia tank stowed on station and the old tank is in place, and that's where Rick and Clay will go up and start to work on the old tank to get it unhooked and pulled off of the truss. We'll bring the arm over and grab that old tank, bring it back around to the front side of the space station's truss and put it on to the cart that we have on the front side of the truss where we can temporarily stow that tank.

"We're then going to go back over and get the new tank which has been temporarily stowed as well over the last couple days. We'll grab that and bring it back and then take off a grapple bar and put it on the back side of the truss so now it's in place. That's a big part of the mission objectives right there.

"Rick and Clay will have a configuration to do on that tank to get it ready, hooking up electrical connections and ammonia lines, and then they'll come back over and help us to grab the old tank, put it back on the arm and we will take it over and install it back in POA again for a temporary stowage until we get to EVA 3."

The spacewalker Rick Mastracchio just manually picked up the tank and handed it over the space station's robotic arm. The arm now has a firm grapple on the tank.

The depleted Ammonia Tank Assembly, a piece of original equipment that was launched with the Starboard 1 truss to the International Space Station in 2002, has been removed by the spacewalkers for today's replacement effort with a fresh supply of coolant for the outpost's thermal control system.

You can see our archived coverage of the Starboard 1's launch on the STS-112 mission of shuttle Atlantis here.

The tank isn't coming off without a little bit of effort. Clay Anderson is fetching a pry bar to assist.

Final unbolting of the tank is underway. The station's robotic arm is poised nearby for the spacewalkers to hand the 1,295-pound assembly over.

Anderson is disconnecting the first of two electrical connectors he's responsible for in the opening task of today's spacewalk that will see the old ammonia tank removed from the space station.

Meanwhile, Mastracchio is getting ready to loosen the first of four bolts holding the tank in place.

Spacewalker Rick Mastracchio previewed today's EVA activities in a pre-flight interview:

"On EVA 2, Clay and I will actually swap out the old ammonia tank for the new ammonia tank so we'll start with removing the old one on the back side of the truss on the space station. We'll remove the old tank. Here's where I will actually lift up the old tank and hand it off to the arm. The arm will take the old tank and move it to the front side of the truss and we will head over there and we will take that tank off the hands of the arm and we will temp stow it on what's called the CETA cart. Basically just tie it down temporarily.

"Then we'll take the new tank that we transferred over from EVA 1. The arm will meet us on the backside of the truss where I will take it from the arm and we will install it, make the electrical connections, make the fluid connections and up the new tank. At that point the space station has a new ammonia tank.

"Then we'll clean up by going back to the old tank and handing it back to the arm where they will begin to temp stow it until we get to put it away permanently on EVA 3."

EVA BEGINS. The spacewalkers switched their suits to internal battery power at 1:30 a.m. EDT, marking the official start time for today's EVA by Rick Mastracchio and Clay Anderson. This is the second of three spacewalks planned during Discovery's mission at the International Space Station.

The EVA is getting underway 46 minutes ahead of schedule.

The depressurization has been completed and the Quest airlock's outer hatch leading to space is being opened.

Depressurization is pausing at 5.0 psi for a planned leak check.

Airlock depressurization has begun.

Rick Mastracchio and Clay Anderson have moved into the section of the airlock that will be depressurized shortly. Now, the inner hatch is being closed by Jim Dutton.

Final steps in the suitup process are being completed in the Quest module now. The spacewalkers are being outfitted with the SAFER backpacks that would enable an untethered astronaut to fly back to the station.

Mission Control projects that today's spacewalk could get underway in about an hour, well ahead of the plan.

And now their helmets are being placed on the spacesuits. Mission Control says the crew's preps are running well ahead of schedule.

The spacewalkers are getting suited up inside the Quest module of the International Space Station.

Astronauts Rick Mastracchio and Clay Anderson are gearing up for a planned 6.5-hour spacewalk early Sunday, the second of three planned by the shuttle Discovery's crew. The goals of this excursion are to install a new ammonia coolant tank on the station's power truss and to move no-longer-needed debris shielding into the station for return to Earth.

Read our full story.

Flight Day 7 has commenced for the space shuttle Discovery astronauts with Mission Control's wakeup. Spacewalkers Rick Mastracchio and Clay Anderson are set to begin their second excursion of the mission at 2:16 a.m. EDT to remove the depleted ammonia tank and plug in the new box on the Starboard 1 truss.

The latest version of the NASA Television schedule (Rev. F) can be downloaded here.


Read our earlier status center coverage.