Live in Orbit: First Spacewalk, Unpacking Ahead

A former Kennedy Space Center engineer will perform maintenance outside the International Space Station later today while crewmates start to move nearly eight tons of gear delivered by shuttle Discovery inside.

Around 3:30 a.m., lead spacewalker Danny Olivas and Nicole Stott will begin a "campout" procedure to help them avoid decompression sickness during a planned six-hour, 30-minute excursion.

They'll breathe pure oxygen to purge nitrogen from their systems and sleep in the Quest airlock at a reduced air pressure of 10.2 pounds per square inch.

They'll awake around 1 p.m. and start the spacewalk - the first of three planned during the 13-day mission - near 6 p.m.

The goal: to remove depleted ammonia tanks on a truss assembly that, at 1,800 pounds, is the largest object to be manhandled by astronauts during assembly and maintenance of the station.

The spacewalkers will also retrieve two sets of European science experiments from outside the Columbus lab and prepare them for return to Earth.

Stott, 46, once oversaw shuttle Endeavour's preparation for flight during a decade of work at KSC. She'll be making her first spacewalk, Olivas his third.

Shuttle and station crew members on Monday hoisted a cylindrical "moving van" from Discovery's payload bay with a 58-foot crane arm and bolted it to a docking port.

It holds more than 15,000 pounds of food, supplies and equipment crucial to the outpost's ability to conduct science research and support six full-time residents.

The equipment includes consoles for materials and fluids research, an air quality system and an unassembled treadmill named for comedian Stephen Colbert.

Before the spacewalk begins, starting around 4 p.m., crew members will begin unloading all that cargo.

Crews already transferred another interesting bit of cargo from the shuttle's mid-deck: a drawer nicknamed a "mice hotel" that houses six mice. They'll stay on the station for about three months as part of an experiment studying bone loss.

Mission controllers on Monday told Discovery's crew that weekend inspections showed no damage to the shuttle's heat shields.

"That's great news," said commander Rick "C.J." Sturckow.

Another inspection will be performed after Discovery departs the station.

Managers also said they were conserving fuel supplies needed to keep the station flying in the correct position for the shuttle's undocking and certain other maneuvers.

For example, a planned dump of excess water produced by the shuttle's electricity-producing fuel cells was cancelled. The water will be bagged and kept on the station.

A leak after Friday's launch disabled six small steering jets on Discovery that would normally have helped control the orientation of the joined spacecraft.

Russian thrusters were to pick up the slack, but used significantly more propellant than expected to rotate the station back into its proper position after Discovery's docking.

LeRoy Cain, deputy shuttle program manager, likened the conservation efforts to choosing to use the most fuel efficient car in your garage. He said they were not a sign of risky shortages that could threaten the mission.

"We're nowhere near any kind of impending issue with the propellant budget on the shuttle or the station in any way at all," he said during a news briefing Monday. "It's just we're trying to be smart about what we're doing."

NASA might use the shuttle's more powerful primary jets for undocking, which could pose risks to the station structure if a jet accidentally fired with too much thrust.