Expedition 13 Commander Pavel Vinogradov and Flight Engineer and NASA Science Officer Jeff Williams also had time set aside each day to continue to become familiar with their orbiting home.
In scientific work, Williams operated the Capillary Flow Experiment, which uses liquid silicone to study how fluids move in a microgravity environment. This portion of the experiment examined the interface between the liquid and the solid surface of the container. The results could be used by designers of systems for future spacecraft.
Williams also set up and activated cameras that will be remotely operated by middle school students to take photos of Earth through the station window. Called the Earth Knowledge Acquired by Middle School Students (EarthKAM) experiment, it allows students to study the Earth and then control a special digital camera mounted on the station. They photograph coastlines, mountain ranges and other geographic items of interest from the unique vantage point of space. More than 112 schools from eight countries have signed up for this session of the experiment. This is the 22nd time the experiment has been performed aboard the station.
Williams and Vinogradov completed the first of three sessions with the Renal Stone experiment, a study of whether potassium citrate can be used to reduce the risk of kidney stone formation. Astronauts have an increased risk of developing kidney stones because urine calcium levels are typically much higher in space. The crew recorded all consumed food and drinks and collected urine samples for later return to Earth. An understanding of the crew's diet during the urine collection timeframes will help researchers determine if the excess calcium in the urine is due to diet or a response to the microgravity environment.
The Expedition 13 crew also spent several hours practicing the use of a manual docking system for next week's arrival of the ISS Progress 21 cargo vehicle. The computer-based training will ensure they're ready to take control of the Progress if the automated system does not work properly. The 21st Progress to visit the station is scheduled to launch from the Baikonur Cosmodrome in Kazakhstan at 12:03 p.m. EDT Monday, and dock with the space station at 1:40 p.m. EDT Wednesday.
A planned reboost of the station was aborted before any engines were fired this week when downlink telemetry showed one of two sunshade covers on the Zvezda Service Module thrusters was not fully open. The station's onboard software detected that the cover was not properly opened and did not ignite the thrusters. The firing was designed to test two thrusters that have not been used since Zvezda docked to the station in July 2000. Zvezda has several other thrusters that could be used if needed. Engineers at the Russian Mission Control Center in Korolev are reviewing data and considering whether additional tests are required.
Friday the crew talked with experts in Mission Control, Houston, about an electrical repair procedure planned for Monday. The pair will replace a failed type of circuit breaker called a Remote Power Control Module (RPCM) in the Destiny Laboratory. The RPCM failed during the last crew's stay aboard the station, and power for several systems has been routed by an alternate path until it is replaced.
Vinogradov and Williams will remain in orbit for six months. During that time, they expect to welcome two space shuttles and perform two spacewalks. European Space Agency astronaut Thomas Reiter will join the Expedition 13 crew when the Space Shuttle Discovery arrives on the STS-121 mission, targeted for launch no earlier than July 1. Reiter will increase the station crew size to three for the first time since May 2003 when it was reduced to conserve supplies following the Columbia accident. The payload operations team at NASA's Marshall Space Flight Center, Huntsville, Ala., coordinates U.S. science activities on the station.