Astronauts Mike Fossum and Piers Sellers donned spacesuits Saturday, preparing for a spacewalk to fix the international space station's rail transporter and test whether a boom can be used to make repairs to the space shuttle.
The 61/2-hour jaunt was to be the first spacewalk for Fossum and the fourth for Sellers.
"Have fun today bouncing on the boom (sounds like a new country song)," flight controllers in Houston wrote in a daily morning electronic message to the astronauts.
In their message, flight controllers told the crew of the space shuttle Discovery that they wanted to take additional pictures of slightly damaged thermal blankets using a camera on the space station.
Controllers do not think two of the blankets pose any problems but want to make sure the other two small blankets don't tear off during re-entry into Earth's atmosphere. The thermal blankets are used to protect the shuttle against soaring heat during ascent and descent.
The flight controllers also had a request for the shuttle crew: Stop pouring unused drinks down the shuttle's toilet. "An example of how closely Big Brother watches," they wrote.
The space shuttle crew awoke Saturday to "God of Wonders," a popular Christian music recording chosen by Fossum's family.
"I do think it's particularly appropriate as I prepare to step outside for about 41/2-trips around this chunk of creation we call Earth," Fossum radioed Houston.
Fossum and Sellers have two main tasks during the first of three planned spacewalks for the 13-day mission.
The first task is to replace a cable cutter on the station's mobile transporter, or railroad car. A duplicate cable cutter accidentally cut a cable leading to the transporter late last year, and NASA wanted to make sure it doesn't happen again. The transporter moves along a space station and is used for constructing the complex which orbits 220 miles above Earth.
The spacewalkers will then test whether a new robotic boom, with astronauts attached at the end, can be used for inspecting or making repairs to hard-to-reach places on the shuttle's underside. Fossum and Sellers planned to simulate repair-related movements while at the end of the boom, which will be attached to the shuttle's 50-foot robotic arm.
The technique was developed to make sure there's never a repeat of the Columbia disaster that killed seven astronauts in 2003. Foam from the shuttle's external tank struck Columbia's wing during launch, creating a breach that allowed fiery gases to penetrate the shuttle during the return flight to Earth.
Fossum and Sellers may get a chance to use the boom for a real repair on their third spacewalk, now scheduled for next Wednesday. NASA managers are evaluating whether a piece of fabric filler protruding from the thermal tiles on Discovery's belly needs to be removed by the spacewalkers.
Two pieces of gap filler had to be removed from Discovery's belly during a spacewalk last year because of concerns they would cause problems during re-entry.