Live: Astronauts Ready For Long Walk

Two Endeavour astronauts may not be able to complete today's busy schedule of repairs during the mission's third spacewalk, NASA mission managers said this morning.

But Heidemarie Stefanyshyn-Piper, who is making her third spacewalk in five days, and Steve Bowen, making his second in as many days, will give it a shot.

The pair, which teamed up for the first spacewalk on Tuesday, is preparing to work outside the International Space Station for at least seven hours, the longest of the mission's four planned spacewalks.

They'll focus entirely on cleaning and greasing a damaged joint that rotates the station's starboard solar wings like paddle wheels, a job begun during the first two spacewalks.

Given the volume of work left and the loss of two grease guns earlier in the mission, station flight director Brian Smith said the some of the work might need to carry over to the fourth planned spacewalk on Monday.

The spacewalk is scheduled to begin at 1:45 p.m., though the previous spacewalks have started up to an hour early. You can watch the whole event live here at The Flame Trench. Just click on the NASA TV picture above to launch a viewer.

The spacewalkers today will have a backup grease gun available in a station airlock. NASA mission managers on Friday approved modifying a caulking gun normally reserved for repairs to the shuttle's reinforced carbon wing edges.

Lead spacewalker Stefanyshyn-Piper said Friday she's rather continue using grease-coated wipes during clean-up of metal shaving debris from the damaged Solar Alpha Rotary Joint, or SARJ. But she did say that alternative technique requires a bit more care and time.

The spacewalkers are now breathing pure oxygen to purge nitrogen from their bodies, to avoid decompression sickness during the spacewalk.

Meanwhile, NASA engineers are still diagnosing the cause of a problem installing the station's new urine processor, a key piece of equipment needed to recycle water to support larger crews of six.

One theory is that a centrifuge in a distillation unit is bumping against another part as it spins, causing sensors to shut down the processor. Officials haven't yet released plans for a fix, but they say Endeavour is still on schedule to bring home water samples needed for testing.

The other half of the water recycling system, called a water processor that recycles sweat and other condensation in the air, is hooked up and running well.

The mission could be extended a day if necessary, a decision that could be made today or Sunday.

Astronauts today also continue to transfer cargo back and forth from the shuttle to the station, including loading some of the garbage and other items that will be returned to Earth in the Leonardo moving van.

Those items must be packed perfectly to maintain the proper center of mass for the cargo carrier and Endeavour as it returns for a landing now scheduled next Saturday around 2 p.m.

You can review today's NASA TV broadcast schedule here.

A detailed timeline and messeages from Mission Control can be found in Execute Package 9.

New to the STS-126 mission? Take a look at the official mission press kit to get up to speed.

Today's wake-up music was played for Shane Kimbrough, who completed his first spacewalk Thursday and will serve as choreographer for today's spacewalk. He's also scheduled to participate in Monday's spacewalk.

The song was "You Are Here" by Dutton.

Kimbrough grew up visiting grandparents in Mims and watching launches from Kennedy Space Center.