NASA managers terminated a spacewalk today when astronaut Chris Cassidy's carbon dioxide levels showed an upward trend due to a problem with his spacesuit's CO2 removal system. NASA managers said late Wednesday his CO2 levels never exceeded normal limits for crews inside the space station or the shuttle and that calling off the spacewalk early was simply a precaution.

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Engineers testing the adhesion of foam insulation on the external tank needed for an August shuttle flight have not found any obvious problems that would raise concern about debris shedding like the foam losses noted during Endeavour's climb to space last week, officials said Wednesday.

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See our story on the spacewalk's conclusion.

To recap, astronauts Dave Wolf and Chris Cassidy planned to replace four aging batteries in the International Space Station's oldest solar array truss today, but spacesuit consumables prompted the EVA to end after only installing two new power packs. The spacewalk, which lasted a total of six hours, began with Cassidy getting Japanese experiments ready for mounting on the station's next external science deck tomorrow.

EVA ENDS. Repressurization of the Quest airlock module is underway, marking the official end of today's spacewalk by Dave Wolf and Chris Cassidy at 4:31 p.m. EDT.

The EVA lasted 5 hours and 59 minutes. That brings the total time for the three spacewalks conducted thus far during Endeavour's mission to 18 hours and 24 minutes.

It was Wolf's seventh spacewalk in his career working outside both the International Space Station and Russia's space station Mir. For Cassidy, this was his first EVA.

The fourth and fifth spacewalks for the Endeavour crew are scheduled to occur Friday and Monday, respectively. Cassidy and Tom Marshburn will perform those excursions. How Mission Control will replan those EVAs to include the leftover battery replacement work, plus a Japanese camera installation and external cargo bracket deployment deferred the two earlier spacewalks is not yet known.

The spacewalkers are following the pre-planned airlock ingress plan with Wolf getting in first, followed by Cassidy floating in last and closing the hatch.

Chris Cassidy is back at the airlock. Dave Wolf is en route.

Based on the carbon dioxide removal system consumables, Mission Control says spacewalker Chris Cassidy needs to head back to the airlock. The astronauts will leave the first old battery that was removed from the station in its temporary stowage location on the side of the truss and the vacant battery port open.

The spacewalkers are re-torquing the bolts holding the battery equipment to the launch carrier.

To recap, two new batteries were installed today and three old ones have been removed. The astronauts were working to retrieve the third new one when the decision was made to end the activities for today.

Mission Control says that the material within the spacesuits used for carbon dioxide scrubbing is going call a close to the spacewalk at this point in the battery replacement task. With the consumables starting to run low and the EVA already beyond the five-hour mark, the crew has been instructed to begin the clean up chores at the worksite. Only two of the planned four new batteries were installed today.

Now passing the five-hour mark into today's spacewalk. The duration is limited to approximately seven hours based on spacesuit consumables.

Spacewalker Dave Wolf has locked the old battery onto the carrier after overcoming a battle with one of the bolts. Next, he will work to get out another new battery for the space station.

The third old battery that's been in space nearly nine years was just disengaged by spacewalker Chris Cassidy and handed to Dave Wolf as the astronauts continue to work together in swapping out the power packs.

Mission Control reports ground teams are seeing good data from both new batteries installed thus far.

The P6 truss has received its second new battery. Two more are planned for this spacewalk.

New battery No. 2 of the day has been unbolted from the launch pallet for the spacewalkers to carry over to the P6 truss installation site.

Spacewalking astronauts Dave Wolf and Chris Cassidy have secured this second old battery into the one open slot on the launch carrier. The original old battery remains temporarily anchored on top of the P6 truss as part of this carefully thought out juggle of new and old power packs.

The second old battery has been removed from its slot on the P6 truss.

The spacewalkers have installed their first new battery on the Port 6 truss, the original power module launched to the International Space Station in November 2000 aboard shuttle Endeavour's STS-97 mission.

The first of the fresh new batteries for the International Space Station's power system has been pulled off the launch carrier by the spacewalkers. The station's arm is holding the carrier as close to the worksite as possible. This particular pallet also carried the spare parts of the station that were unloaded during Monday's spacewalk. The structure will hold the old batteries during their return to Earth aboard the shuttle.

The first battery has been removed by spacewalker Chris Cassidy. It will be temporarily stowed nearby while the spacewalkers retrieve a new battery from the launch carrier and install that. This initial old battery will get stowed in the carrier later in the EVA.

Out at the worksite now, Chris Cassidy is installing handholds onto the first battery that will be removed from the Port 6 truss.

The spacewalkers have begun making their way to the far port side of the space station's truss for replacement of batteries in the P6 power module. Details on the battery work can be read in our morning preview story.

Dave Wolf, on his seventh career EVA, is working on the Destiny lab module installing thermal sleeves around umbilicals and tucking down some cables.

The final cover has been removed by Cassidy, along with releasing a launch lock. This completes the work at the Japanese Exposed Facility for today's spacewalk.

The third cover has been thrown clear of the space station by Chris Cassidy.

Another good jettison by Chris Cassidy of a second thermal cover.

Over at the Harmony connecting module, Dave Wolf is removing an equipment installation socket and handrail to clear any obstructions for the upcoming arrival of Japan's first automated resupply ship. He'll take the handrail and socket over to Europe's Columbus laboratory and reinstall them there.

After removing the first thermal cover, Chris Cassidy balled up the white blanket and then tossed it overboard.

Chris Cassidy, on his first spacewalk, has traveled along the Kibo laboratory module and onto the Japanese Exposed Facility to reach the small experiment carrier that was attached yesterday. He will remove some covers and complete the necessary hands-on work so that the three packages can be plucked off the carrier and installed directly onto the science deck tomorrow by Japan's robot arm. That carrier will be returned to Endeavour later in the mission for the trip back home.

Wolf and Cassidy have egressed the airlock and heading toward their initial work sites in the early portion of this spacewalk. Wolf will be going to Harmony module for the relocation of some equipment in preparation for attachment of the Japanese HTV cargo ship later this year. Cassidy is en route to the new Japanese external science deck to ready the experiment packages for their removal from a launch carrier by the Kibo robot arm tomorrow.

EVA BEGINS. The spacewalkers switched their suits to internal battery power at 10:32 a.m. EDT, marking the official start time for today's EVA by Dave Wolf and Chris Cassidy. This is the third of five spacewalks planned during Endeavour's mission at the International Space Station.

Running almost a half-hour ahead of schedule, the outer hatchway to space has been opened following depressurization.

Depressurization of the space station's Quest airlock to vacuum for today's spacewalk has begun.

The spacewalkers have been assisted into the airlock by their fellow astronauts and the inner hatchway has been closed.

Astronauts David Wolf and Christopher Cassidy are preparing for a challenging spacewalk today, working at the far left end of the International Space Station's long power truss to replace four of six aging batteries in the lab's oldest set of solar arrays.

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

Astronauts Dave Wolf and Chris Cassidy have donned their spacewalking spacesuits as preps proceed smoothly for today's EVA.

Flight Day 8 has begun for the astronauts after a musical wakeup call from Mission Control in the form of "Santa Monica" performed by Everclear.

Read our earlier status center coverage.