Expedition 16 commander Peggy A. Whitson participated in the 100th spacewalk for the construction and maintenance of the International Space Station. During the historic 6-hour, 56-minute spacewalk, Whitson and flight engineer Daniel Tani (out of frame) looked for the cause of partial loss of electrical power to one of the station's two Beta Gimbal Assemblies for starboard solar wings and examined damage to the starboard Solar Alpha Rotary Joint. The spacewalk took place on Dec. 18, 2007.