After extensive pressure checks on Saturday and Sunday in the Russian Progress resupply ship, the Pirs Docking Compartment, the Soyuz return vehicle and the U.S. Quest Airlock revealed no leaks, the crew used an ultrasound leak detector device for a second time at the Lab window, and detected an audible hissing noise emanating from the flex hose. That hose is hooked up to quick disconnect devices as part of a system designed to vent into space any condensation between the panes of glass to maintain the window's optically pristine quality.
Foale said he couldn't hear any hissing noise from the flex hose during a previous leak check last week because of other ambient noise generated by operating payload racks in Destiny. Sunday, those racks were shut down for a short time and the hissing noise was obvious. Foale reported that as soon as the flex hose was disconnected, the noise stopped. While additional evaluation is needed for confirmation, the pressure in the Station appears to have stabilized since the removal of the flex hose.
Although the leak may now be fixed, flight controllers are planning to ask the crew to close several hatches aboard the station this weekend, dividing the complex into three sections to allow further leak checks and to gather additional baseline data on normal air pressure fluctuations in portions of the Station. Flight controllers will monitor the pressure in each section during the weekend to gather air pressure data. All of the hatches are planned to be reopened Sunday night. The isolated sections will include the U.S. Destiny Lab; the Zarya Control Module, Quest Airlock and Unity Node; and the Zvezda Service Module, Pirs Docking Compartment, Soyuz rescue vehicle and Progress resupply vehicle. While the hatches are closed, the crew will remain in the section that includes the Zvezda living quarters module. To prepare, they will begin moving some additional equipment into the living quarters on Friday. Foale normally sleeps in the Destiny Lab while Kaleri normally sleeps in Zvezda.
Foale and Kaleri repaired the Russian Elektron oxygen generation system today and are scheduled to press ahead with repairs to the Vozdukh carbon dioxide removal system in the next week or so. In preparation for the Elektron repair work, the pressure in the ISS was increased late Sunday to about 14.2 pounds per square inch, using remaining oxygen in the Progress resupply ship tanks. The Progress will be discarded in about two weeks in advance of the launch of a new resupply vehicle on Jan. 29 carrying food, fuel and supplies for the crew.