Expedition Four Commander Yury Onufrienko and Flight Engineers Carl Walz and Dan Bursch, beginning their 10th week on orbit, received volumes of information and training materials from the flight control team on the ground, participated in computer-based training sessions, and checked out the spacesuit, airlock and experiment systems that will be used Feb. 20. A full dry-run of the airlock depressurization is planned Friday.
The excursion will mark the first use of the station's airlock since July 2001 and will test equipment and techniques that will be used during the April STS-110 assembly mission, when four spacewalks out of the Quest airlock will install the first piece of the station's structural and electrical "backbone." Bursch and Walz will perform a checkout of the airlock's systems, connect and disconnect several electrical cables, remove insulation blankets from the Z-1 truss structure and bring inside several tools to expedite the work planned for STS-110.
They will use U.S. space suits, with Walz, wearing a suit with red stripes on the legs and Bursch wearing an all-white suit. The spacewalk is scheduled to begin at about 6 a.m. CST Wednesday. NASA Television coverage will begin at 5:30 a.m. CST Wednesday. Experiment work also continued aboard the station, as crew members set up and activated the second Advanced Astroculture experiment. The investigation will grow mustard plant seeds harvested on board the station by the Expedition Two crew and returned after analysis on Earth, making them a true second generation of space-grown plant life. The University of Wisconsin-sponsored experiment studies Arabidopsis thaliana, which is renowned in genetic research circles as a key to identifying genes and determining their functions for entire classes of similar organisms.
The crew disassembled the Active Rack Isolation System, which suffered a push-rod failure, and will soon conduct repairs that will enable the system to resume its work. The system protects sensitive microgravity experiments from the motions caused by everyday crew life aboard the station.
The crew also worked with flight controllers on the ground to complete some unplanned maintenance work after Sunday's failure in a Remote Power Conversion Module (RPCM) that distributes power to a variety of station systems. Full functionality was restored to the non-critical systems that were affected in the Destiny laboratory module after Bursch and Walz replaced the glorified breaker box with an onboard spare. To access the module, they removed Bursch's temporary sleep station and replaced it, installing additional high-density plastic radiation protection bricks while they had the opportunity.
A planned upgrade of the station's software was postponed until after the Feb. 20 spacewalk to allow software engineers on the ground to perform one last set of tests to verify all aspects of the software load. The new software will prepare the station's computer systems for the arrival of the truss structure and other components to be delivered on STS-110 and future flights.