Live in orbit: Port rotary joint "nice and clean"

Spacewalking astronaut Douglas Wheelock is getting ready to ride the shuttle's robot arm on a spare parts delivery mission.

Operating the 50-foot crane from the flight deck of Discovery, pilot George Zamka will haul Wheelock from the U.S. Destiny laboratory at the International Space Station down into the shuttle's cargo bay. There, Wheelock will unbolt a spare power distribution box. About the size of a small referigerator, the 525-pound Main Bus Switching Unit will be hoisted up to an external stowage platform outside the U.S. Quest airlock.

Mission specialist Scott Parazynski just finished releasing cinches from a fold-up radiator on the side of the newly installed P6 truss. Ground controllers then sent computer commands to deploy the 40-foot-long heat-dissipator.














He also inspected the station's portside rotary joint as part of an investigation into trouble with an identical joint on the starboard side of the outpost. Parazynski removed a thermal cover and reported no debris inside.

"I have a happy story," he said. "I don't see any filings."

Parazynski said the joint is "nice and clean." He snapped a series of digital photographs that will be downlinked to engineers in Mission Control later today.














Station flight engineer Dan Tani found metal shavings inside the joint on the starboard side of the central truss -- an indication that gear teeth or other internal components are being sheered when it rotates.

The 10-foot-wide rotary joints are designed to turn like Ferris wheels so station solar wings can constantly track the sun, maximizing electrical output. The starboard joint has been fixed in a stationary position until the problem can be rectified. Power-generation is significantly reduced as a result.

An extensive inspection now is planned on Thursday -- during the fourth of five spacewalks scheduled during Discovery's stay at the station.

Still to come: The big events of the day. The separate deployments of the twin solar wings on the P6 truss are coming up at 11:58 a.m. and 12:58 p.m. EDT.

You can watch all the action unfold right here in The Flame Trench. Simply click the link below the top image to launch our NASA TV viewer and round-the-clock coverage of the STS-120 mission. Be sure to refresh this page for periodic updates.