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Saturday, April 25, 1998, 1 a.m. CDT
STS-90 Mission Control Center Status Report # 16

Due to problems with equipment which removes carbon dioxide from the cabin atmosphere, Columbia’s crew went to bed about two hours late Friday and will awaken at 6:39 a.m. CDT, about an hour later than originally scheduled.

The crew’s sleep period was scheduled to begin at 9:39 p.m. CDT Friday, but at about 10:45 p.m. CDT, the Regenerative Carbon Dioxide Removal System aboard Columbia shut down, ringing a cautionary alert onboard. Flight controllers asked the crew to switch to a second set of control electronics for the unit and restart it. However, about 10 minutes later, the equipment shut down again. At that point, flight controllers asked the crew to install backup carbon dioxide-absorption canisters in the laboratory and crew cabin. Called lithium hydroxide canisters, a supply is stored aboard Columbia as a backup to the recyclable system which shut down.

The lithium hydroxide canisters are not recyclable and must be replaced daily with fresh canisters as they become saturated with carbon dioxide. Members of the crew were still awake when the problem occurred, with some crew members still wrapping up science work in the payload bay laboratory.

The crew was never in any danger due to the equipment problems and carbon dioxide levels in the crew cabin always remained normal. Flight controllers will continue to evaluate the problem with the recyclable carbon dioxide removal system and may ask the crew to perform further troubleshooting activities after they awaken. Due to the later wake-up time, a few activities planned for early in the crew’s day have been canceled, including a ship-to-ship conversation by the crew of Columbia with astronaut Andy Thomas on Mir.

However, members of the crew remain scheduled to talk with students in three events during the day. Commander Rick Searfoss, Payload Commander Rick Linnehan and Payload Specialist Jay Buckey will speak with students at the McAuliffe Planetarium in New Hampshire at 11:39 a.m. CDT. Canadian Space Agency astronaut Dave Williams will speak with students at York University in Ontario, Canada, at 3:49 p.m. And Buckey will talk with students at Dartmouth College at 4:34 p.m.

And, from Mir, Thomas remains scheduled to answer questions sent to him by Australian school students at 9 a.m. CDT


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