The Leonardo Multi-Purpose Logistics Module (MPLM) was unberthed from the payload bay early this morning by Commander Ken Cockrell operating the shuttle's robotic arm to move the module to the station's Unity module. Leonardo's installation proceeded perfectly with completion at 9:28 a.m. Central time. About 4:30 p.m. Central time, the MPLM's hatch was opened. Dan Bursch of Expedition Four called down at 4:52 pm that all crew members had entered the logistics module and were working to get the transfers rolling. The crew got a good start on the movement of more than 5,600 pounds of cargo to the station.
Early today, one of four control moment gyroscopes used in the station's attitude control system experienced a mechanical failure. Flight controllers turned it off and began using the remaining three gyros to maintain the station's attitude. It is believed that one of its spin bearings failed, causing it to seize. Flight Engineer Carl Walz reported that the crew could feel and hear "growling" vibrations as it failed. While the failure is a serious complication for the long-term space station operations, there are multiple backup systems for control of the station's attitude so it poses no threat to the safety of the shuttle or expedition crews. The situation is expected to require only minor changes to the STS-111 flight activities.
Franklin Chang-Díaz, and Perrin, with help from Paul Lockhart, readied their extravehicular mobility unit space suits and tools, and reviewed procedures for Sunday's spacewalk. The two first-time spacewalkers will install a Power and Data Grapple Fixture (PDGF) to the station's P6 solar array truss and temporarily store some Russian meteoroid/debris shields. They'll also remove thermal blankets from the Mobile Base System (MBS) in Endeavour's cargo bay, and support its unberthing. The MBS will be parked on the shuttle's arm near its installation point so that hardware temperatures can equalize before it is attached to the existing Mobile Transporter platform. At the end of the day, flight controllers will activate the MBS from the ground in preparation for the next day's operations. Chang-Díaz also will inspect and photograph the exterior condition of station's failed control moment gryoscope at the end of his spacewalk.
The combined STS-111 crew of Cockrell, Lockhart, Chang-Díaz, Perrin, Yury Onufrienko, Dan Bursch and Carl Walz will wake up at 4:23 am CDT Sunday, while new station Commander Valery Korzun and Flight Engineers Peggy Whitson and Sergei Treschev will arise at 4:53 am.