Spacewalking astronauts discovered some unwanted wear on a giant solar wing rotary mechanism on the port side of the International Space Station's central truss. But they said the wear was not nearly as extensive as damage done to a twin mechanism on the starboard side of the truss.
Endeavour mission specialists Shane Kimbrough spotted the wear and told crewmates that it was "a junior version of what we have on the other side."
Kimbrough is lubricating the joint as preventative maintenance aimed at avoiding the type of grinding damage that forced NASA to shut down an identical solar wing rotary mechanism on the starboard side of the truss in September 2007.
The Solar Alpha Rotary Joints are 10-foot-diameter mechanisms designed to turn solar wings like paddlewheels so they can constantly track the sun as the station circles Earth. The starboard joint has been kept stationary since internal damage was found.
Endeavour mission specialist Steve Bowen now is finishing up repair work on the starboard joint. He is cleaning up metal shavings on the surface of a giant saw-tooth gear, and he also will replace the last of 12 bearing assemblies placed around the circumfernce of the so-called race ring.
Ten of the bearing assemblies were replace during three spacewalks last week. Another was removed and replaced as part of a troubleshooting effort earlier this year.
NASA hopes to test the joint early tomorrow to determine how well the unprecedented repairs worked.
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