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Saturday, May 2, 1998, 5 p.m. CDT
STS-90 Mission Control Center Status Report # 32

With all science activities complete on board, Columbia’s seven astronauts readied their ship for a Sunday landing at Kennedy Space Center.

The science crew – Mission Specialists Rick Linnehan and Dave Williams, and Payload Specialists Jim Pawelczyk and Jay Buckey -- wrapped up science activities this morning with final studies focusing on how the vestibular system adapts in a changing environment.

To prepare for tomorrow’s return to Earth, the flight crew – Commander Rick Searfoss, Pilot Scott Altman and Mission Specialist Kay Hire – conducted a successful test of the shuttle’s reaction control system jets and flight control surfaces. For the check out of the flight control surfaces, the astronauts started Auxiliary Power Unit #3, one of three hydraulic units on board, to provide hydraulic power to the surfaces and to verify that its cooling system was working properly after an apparent freeze-up during Columbia’s launch two weeks ago. The FCS checkout was completed successfully, but APU 3’s cooling system did not function as expected.

The failure of the cooling system for APU 3 will not affect Columbia’s landing tomorrow and a minor modification to managing the auxiliary power units will be implemented by entry Flight Director John Shannon. Following standard deorbit procedures, one APU will be started five minutes prior to the scheduled deorbit burn. At a point 13 minutes before Columbia encounters the first traces of the atmosphere, when the remaining two APU’s are normally brought on line, only one additional APU will be started. APU 3 will be powered on about six minutes prior to landing when Columbia’s speed is about Mach 2.5. The auxiliary power units are capable of operating for 10 to12 minutes before their cooling systems would be required.

Commander Rick Searfoss successfully dumped about 70 pounds of waste water into a Contingency Waste Container (CWC) this morning, This will ensure sufficient stowage capacity in the waste tank to support as much as two additional days in orbit in the event Columbia does not land on Sunday.

Payload commander Rick Linnehan replenished water supplies and performed some routine husbandry tasks for the rodents on board and completed a partial deactivation of the Spacelab module. Final deactivation of Spacelab systems is set for tomorrow morning. Columbia’s Ku-band communications antenna also was stowed about 11:30 a.m. today.

Columbia has two opportunities to land at the Kennedy Space Center on Sunday. The first would see a deorbit firing of the orbital maneuvering system engines at 10:11 a.m. CDT, with landing at 11:09 a.m. In the event flight controllers elect to bypass the first opportunity, there is a second opportunity that would see a deorbit burn at 11:44 a.m. with a landing to follow at 12:43 p.m. CDT. Preliminary weather forecasts for Sunday show clear skies in the vicinity of the Kennedy Space Center, with the only potential issue the possibility of high cross winds. The current forecast indicates the winds should stay within acceptable limits.

By Monday, a weather front is expected to approach KSC, bringing with it the possibility of low cloud ceilings and rain showers. Weather at the alternate landing site at Edwards Air Force Base in California is expected to be good through Tuesday. The next STS-90 status report will be issued following Columbia’s landing at the Kennedy Space Center, or after a wave-off of Sunday landing opportunities.


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