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Saturday, April 25, 1998, 7:15 a.m. CDT
STS-90 Mission Control Center Status Report # 17

The STS-90 astronauts will begin the start of their second week of on-orbit science operations today, and also will support some troubleshooting procedures following the shutdown of a carbon dioxide removal system last night.

Flight controllers on the ground continue to review data associated with the Regenerative Carbon Dioxide Removal System (RCRS) unit aboard Columbia which shut down late last night. Engineering teams will meet this morning to consider what troubleshooting activities they may ask the crew to undertake later today to try to recover the RCRS system.

With the regenerative system at least temporarily unavailable, the crew has installed the backup carbon dioxide-absorption canisters in the laboratory and crew cabin. A supply of 28 lithium hydroxide canisters is available aboard Columbia. The canisters are a passive and very reliable CO2 removal system.

Should a decision be made that the RCRS system cannot be recovered, the 28 lithium hydroxide canisters available onboard Columbia would allow about five more days of science operations to be conducted before the mission would have to be concluded. Approximately four canisters are needed each day to support the removal of CO2 from the crew cabin and laboratory environments. Eight canisters would be held in reserve to support the two day landing wave-off reserve in case weather or technical problems delayed Columbia’s return to Earth.

Crew members also may work with an air circulation fan associated with the Rodent Animal Holding Facilty (RAHF) being carried in the Spacelab. Data indicate that a fan associated with RAHF unit #7 may no longer be working. These fans are important to the health of the animals being carried in the RAHF as they deliver fresh air into the RAHF and facilitate the removal of CO2. Current plans call for the crew to run a malfunction procedure to determine if the #7 unit fan has in fact failed. If it has, the crew will then perform an in-flight maintenance procedure to set up a bypass system that will allow the fan in RAHF unit #3 to support the #7 unit.

Science operations for Flight Day Nine will include continued work with the ball catch experiment which is part of the Sensory Motor and Performance Team. The ball catch experiment utilizes an apparatus that propels a ball from above in a downward motion toward a seated astronaut. Investigators will monitor the astronauts performance to see if the crew uses visual cues to compensate for the cues missing in a microgravity environment.

The crew also will perform more work with the Effects of Gravity on Postnatal Motor Development Experiment which is one of the Mammalian Development Team’s projects. Ground research has indicated that gravity plays a significant role in how rats learn basic motor skills such as swimming and walking. The rats being studied in this experiment were launched when they were only a few days old and scientists will be looking to see if motor skills develop normally in the weightless environment. The rats will be videotaped as they move around in a special walking apparatus that has various surfaces to allow them to walk and climb. Additional motor skill tests will be performed after the flight to see if the rats are able to readapt to the force of gravity.

Columbia remains in a 153 x 133 nautical mile orbit, circling the Earth every 90 minutes.

The next STS-90 status report will be issued about 6 p.m. Saturday or as events warrant.


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