Mission Specialists Leroy Chiao and Bill McArthur completed the third successful spacewalk of Discovery's STS-92 mission at 4:18 p.m. CDT Tuesday, installing two DC-to-DC converter units atop the International Space Station's new Z1 Truss. Those two 129-pound converters, called DDCUs, will convert electricity generated by the huge solar arrays to be attached during the next shuttle mission to the proper voltage.
Today's spacewalk began at 9:30 a.m. and ended at 4:18 p.m., almost exactly as planned. Total time of Tuesday's EVA was 6 hours, 48 minutes. That brings to 20 hours, 23 minutes the total time of the three spacewalks performed thus far in Discovery's mission, and the total time of space station construction spacewalks to 62 hours, 38 minutes. A fourth spacewalk is scheduled for Wednesday. It too will prepare the Z1 Truss for attachment of the solar arrays.
Chaio and McArthur were helped by the robot arm in moving around the station. Koichi Wakata and Mike Lopez-Alegria split the arm-operation duties on Tuesday, with Lopez-Alegria taking the first half.
The spacewalkers also completed power cable connections on both the Z1 truss and newly installed docking port, PMA-3. They connected and reconfigured cables to route power from Pressurized Mating Adapter-2 to PMA-3 for the arrival of Endeavour and the STS-97 crew next month. They also attached a second tool storage box on the Z1 truss, providing a place to hold the tools and spacewalking aids for future assembly flights. McArthur stocked the boxes with tools and hardware that had been attached to the Unity module. STS-96 Astronauts Tammy Jernigan and Dan Barry had left the tools on the outside of Unity during a May 1999 spacewalk.
After today's spacewalk, Discovery Commander Brian Duffy and Pilot Pam Melroy completed the second of the three station reboosts scheduled for STS-92. They fired reaction control system jets in a series of pulses of 1.4 seconds each, over a 30-minute period, gently raising the station's orbit by about 1.7 statute miles.
On Wednesday astronauts Jeff Wisoff and Lopez-Alegria are scheduled to perform the fourth and final spacewalk of the STS-92 flight. Among activities will be deployment of the Z1 utility tray, and opening and closing of the Z1 Manual Berthing Mechanism latches. Wisoff and Lopez-Alegria also will test the SAFER, or "simplified aid for EVA rescue," a backpack that could enable an astronaut drifting away from the shuttle or the station to get back to the spacecraft. Finally, they will test methods for rescuing an incapacitated astronaut.
The next Mission Control Center status report will be issued at 6 a.m. Wednesday, or as events warrant.
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