Expedition 12 Commander Bill McArthur and Flight Engineer Valery Tokarev spent several days replacing worn components, inspecting and cleaning other parts of the treadmill. The Treadmill Vibration Isolation System floats in a pit in the floor of the station's Zvezda living- quarters module. A complex system prevents crew treadmill running from shaking the station's structure and experiments.
Following a final test run and inspection on Wednesday, the crew began normal use of the treadmill. The treadmill is one of several exercise options available on the station. Other equipment includes a stationary bicycle and a resistive exercise device that uses tension to simulate weights. Exercise is important to counteract the physical effects of long duration weightlessness.
A special activity is planned next week to test procedures that could shorten the preparation time required for future spacewalks. The crew and Mission Control call it a "camp out" since McArthur and Tokarev will shut themselves in the Quest Airlock overnight. They will lower the air pressure to 10.2 pounds per square inch (psi). That is approximately equal to the air pressure found at the 10,000 foot elevation level on Earth. The station is kept at 14.7 psi, which is near Earth sea-level pressure.
Spending the night at the lower air pressure helps flush nitrogen from the body faster, preventing decompression sickness. The new procedure can reduce the amount of time crew must breathe pure oxygen before a spacewalk to complete the purge. For the test, the crew will follow many of the same measures as if performing a spacewalk, but they will not don their spacesuits. The crew will enter the airlock around the start of its sleep period Thursday afternoon. They will return to the main station modules early Friday morning.
In preparation for the camp out, McArthur worked in the Destiny Laboratory to replace a faulty component in the device that can measure the composition of the station's air. On Thursday, he installed a new spectrometer in the mass constituent analyzer. An attempt by Mission Control to power up the unit early Friday was unsuccessful, and McArthur was asked to do more troubleshooting. The problem may be the device's electrical connectors are not seating properly. Engineers are analyzing the problem, and McArthur may do more troubleshooting this weekend.
In science work this week, the EarthKam experiment completed its most recent session on Saturday. EarthKam uses a camera to take photos of Earth through the station's window of locations selected by students on Earth. More than 1,900 students from 118 schools participated in the session.
Schools participated from: the United States, Canada, Argentina, Germany, Spain, United Kingdom, Belgium, Japan, and, for the first time, New Zealand. The images will be used in a wide-range of studies, including coastline erosion, deforestation and environmental impacts. Approximately 1,000 schools have participated in EarthKAM, with students taking nearly 20,000 photos.