Hasty repair set for space

Facing two problems with the solar arrays that power the International Space Station, NASA decided Wednesday to pour all its efforts into fixing one of them, a torn solar sheet that has cut power to the station by 3%.

To fix it, a spacewalking astronaut will be placed on the end of a boom in space to try and free a snagged power line that is preventing the solar panels from fully deploying.

The repair, which will take place either Friday or Saturday, caused NASA engineers to scramble to orchestrate a mission in days that would normally take weeks of careful planning and rehearsals. In the balance is the safety of spacewalker Scott E. Parazynski, who must be careful not to touch the sunlight-collecting panels or damage the solar array in any way.

The array, a collection of solar panels that unfold into long wing-like projections from the station, provides 20 kilowatts of power. That’s about equal to the amount used by four or five homes on Earth.

The station has enough power from its other solar arrays to keep its three-person crew comfortable. But NASA needs to get all its power-generating systems working to accommodate new Japanese and European laboratories scheduled to be delivered over the next few months.

The plan is to use the space station’s robotic arm to hold a second robotic arm from the shuttle Discovery, which is parked at the station. Parazynski will be positioned on the end of the second arm.

While the solar panels are covered with insulating material, NASA officials said they want him to avoid contact with any electrical circuitry, in case the protective covering has eroded in space.

“Our rule is, ‘Don’t touch the array,’ ” Mike Suffredini, NASA’s space station program manager, said at a news briefing Wednesday at Johnson Space Center in Houston.

By concentrating on the torn solar sheet on the port side of the station, NASA has decided to temporarily set aside a problem with a rotating joint on the starboard solar arrays. That piece of equipment, called a solar alpha rotary joint, has malfunctioned, preventing the panels from tracking the movement of the sun.

In an earlier spacewalk, Discovery astronaut Daniel M. Tani looked inside a thermal blanket covering the rotating joint and saw what looked like metal shavings. Any repair to the rotary joint must now take place after Discovery undocks Monday for a planned Wednesday landing.

NASA officials said they hoped to conduct the torn solar sheet repair on Friday. But shuttle flight director Derek Hassmann said it might not happen until Saturday.

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john.johnson@latimes.com