The Expedition 4 crew began their week by having Sunday, Monday and half of Tuesday off after playing host to three visitors for more than eight days. The multinational Soyuz Taxi crew left the International Space Station Saturday, May 4, having delivered a fresh Soyuz crew return vehicle to the outpost.
Onufrienko, Walz and Bursch also worked with the Zeolite Crystal Growth experiment and the Biomass Production System, a plant growth experiment that is the second such experiment for the Expedition 4 crew.
Russian ground controllers continue to work with Onufrienko to troubleshoot the Elektron oxygen generating system in the Zvezda Service Module, which has been working off and on for most of the last week. The Elektron, which breaks down water into hydrogen and breathable oxygen, is off. When necessary, the crew has been burning chemical candles that release oxygen and have resupplied the ISS with oxygen from the Progress supply tanks. Although they do not plan to use it, the crew has an additional supply of oxygen in the high-pressure gas tanks attached to the station's Quest airlock. The Elektron problem has had no impact on station operations.