The servicer contains spare ammonia that can be used in the space station's cooling systems if needed. The Materials ISS Experiment (pronounced 'missy' by its acronym) will expose 750 material samples to the space environment for about 18 months before being returned home late next year. During the space walk, Discovery's Commander Scott Horowitz operated the shuttle robot arm, and Pilot Rick Sturckow choreographed the space walk from the orbiter's flight deck. This was the 25th space walk devoted to the construction of the space station and the 12th this year. Barry and Forrester will perform the mission's second space walk on Saturday to hook up heater cables for another truss structure to be delivered to the station next year. Mission managers Friday will evaluate the consumables onboard Discovery and assess the progress made by the crews in transferring items into the Leonardo logistics module from the station before making a determination as to whether the docked phase of the flight should be extended by one day.
Earlier today, the computers inside the Zvezda module once again assumed control of the station's attitude - or position in space -- after Russian flight controllers completed the loading of upgraded software commands to those computers. In the meantime, Discovery maintained control of the complex until the computer upgrades were completed with no impact to station operations.
The Expedition Three crew --Commander Frank Culbertson, Pilot Vladimir Dezhurov and Flight Engineer Mikhail Tyurin -- earlier today offered commemorative remarks on the occasion of the 1000th day in space for the International Space Station since the Zarya module was launched on Nov. 20, 1998 from the Baikonur Cosmodrome in Kazakhstan.
Discovery and the station are orbiting the Earth every 90 minutes at an average altitude of 244 statute miles with all systems functioning normally.