The International Space Station’s Expedition 39 crew performed microgravity research and spacesuit maintenance Wednesday while awaiting next week’s arrival of a Soyuz spacecraft that will double the station’s population.

Commander Koichi Wakata began the day with a quick test of the station’s drinking water using the Total Organic Carbon Analyzer, making sure that the recycled water remains free of contaminants.

Afterward the Japan Aerospace Exploration Agency astronaut replaced a manifold bottle in the Combustion Integrated Rack. This facility, which includes an optics bench, combustion chamber, fuel and oxidizer control and five different cameras, allows a variety of combustion experiments to be performed safely aboard the station. Fire quite behaves differently in the absence of gravity, and the experiments performed in this facility could lead to improvements in spacecraft materials selection and strategies for putting out accidental fires aboard spacecraft. The research also provides scientists with improved computational models that will aid in the design of fire detection and suppression systems here on Earth.

Wakata also replaced some burned-out light bulbs in two of the eight EXPRESS racks aboard the complex. Short for EXpedite the PRocessing of Experiments for Space Station, EXPRESS racks support a variety science experiments in any discipline by providing structural interfaces, power, data, cooling, water and other items. Each EXPRESS rack can accommodate up to ten small payloads.

Flight Engineer Rick Mastracchio of NASA meanwhile deployed a new control unit for the Space Acceleration Measurement System, or SAMS, and transferred its related software to a new laptop computer. SAMS is an ongoing study of the vibrations and accelerations on the station resulting from the operation of hardware, crew exercise, dockings and activities such as the debris avoidance maneuver Sunday night to steer the station clear of a piece of satellite debris.

After a break from lunch, Mastracchio and Wakata teamed up in the Quest airlock for some spacesuit maintenance to make sure that the equipment remains ready to support a spacewalk. With guidance from NASA astronaut Doug Wheelock serving as Capcom at Houston’s Mission Control Center, Mastracchio and Wakata replaced a Condensate Water Relief Valve Filter inside of one the four U.S. spacesuits aboard the station. New parts and a new spacesuit will be coming up to the station aboard the SpaceX Dragon cargo craft, and a spacesuit with a defective sublimator will return to Earth aboard Dragon at the end of its mission. The departing spacesuit is not the one worn by European Space Agency astronaut Luca Parmitano during a July spacewalk that was terminated early when the helmet began to fill with water. That spacesuit was repaired on orbit by the station crew and returned to service. The SpaceX-3 commercial resupply services flight is targeted for launch no earlier than March 30.