Managers decided to postpone the planned station "campout" this week until next month. It will test procedures to shorten the preparation required for spacewalks. It was delayed after a device called the Major Constituent Analyzer (MCA) could not be activated following maintenance work by the crew. The device measures the composition of the station's air.
McArthur replaced a major component of the MCA last week, the mass spectrometer, but attempts to activate the unit were unsuccessful. McArthur continued troubleshooting the device Saturday. Engineers suspect the problem may be damaged electrical connectors and are evaluating ways to fix them.
The crew began preparations for the next shuttle mission, STS-121, targeted for launch to the station no earlier than May. McArthur made room in the storage racks inside the Destiny lab for new equipment scheduled to arrive on Space Shuttle Discovery.
He cleared space in EXPRESS Rack 3 for a European Space Agency experiment facility called the European Modular Cultivation System. The facility will house biological experiments dealing with the effects of gravity on plant cells, roots and physiology.
Tokarev and McArthur also continued packing the station's Progress 19 cargo spacecraft with trash, readying it to undock March 3. The supply craft's thrusters were used a final time to reboost the station Wednesday, increasing the altitude by eight miles.
McArthur continued science work, performing his third session with an experiment called Foot/Ground Reaction Forces During Spaceflight. The experiment investigates how muscles and joints of the legs and feet are used differently in space than on Earth. To gather data, McArthur wore the instrumented Lower Extremity Monitoring Suit, which measures joint angles, muscle activity and forces on the feet as he exercised. The experiment measures the musculoskeletal system and may lead to a better understanding of bone loss during long-duration missions.
The SuitSat experiment, an unneeded Russian Orlan spacesuit-turned-satellite, has stopped sending signals. SuitSat was released by Tokarev during a spacewalk Feb. 3. It transmitted recorded voices of school children to amateur radio operators as it orbited the Earth. Hundreds of reports from individuals receiving the faint signal from all over the world were logged at the project's Web site.