With a visit by the Space Shuttle Atlantis a little over a week away, International Space Station flight controllers plan to conduct a final rehearsal of the station's activities for the upcoming docking on Tuesday.
This week, station controllers completed transferring propellants from tanks aboard the attached Progress cargo craft to tanks aboard the Zvezda living quarters module. Controllers in the United States and Russia also conducted a test of the efficiency of the solar arrays on the Zvezda and Zarya modules, finding everything in good shape.
An evaluation of problems with two batteries on the station -- one in Zarya and one in Zvezda -- continued this week, although the problems have no impact on any planned station activities. The problem exhibited by the battery in Zarya, labeled Battery 6, is consistent with normal signs of aging, and battery 6 is already planned to be replaced during Atlantis' visit. The problem with the battery in Zvezda, called Battery 4, is believed to be caused by an electronics unit, called the PTAB, that is associated with the battery's charging and discharging. The problem is not believed to be with the battery itself. At present, Battery 4 is not in use, and the PTAB is planned to be replaced during Atlantis' visit. The four other batteries aboard Zvezda are operating normally.
Late last week, one of the three flight control computers aboard Zvezda was automatically taken off line. To backup one another, three computers operate simultaneously aboard the module, performing the same functions. The other two computers are on line and continuing to operate well and there is no impact to the station's activities. The station can operate on only one computer if necessary, and the docking of Atlantis could proceed using ground commanding to control the station even if no computer was on-line. Analysts at the Russian Mission Control Center in Korolev have dumped the off-line computer's software and are evaluating it. Since the computer has been off-line, it has remained operating and controllers have seen no other problems.
As they continue to evaluate the station's orbit in preparation for the rendezvous of Atlantis, station flight controllers will make a final decision this weekend on whether a final engine firing tentatively planned next week will be needed. On Tuesday, controllers will briefly maneuver the station to the orientation required for the Shuttle docking in a test of the docking procedures. On Sept. 8, the day Atlantis is planned to launch from the Kennedy Space Center, station controllers will turn on heaters to begin warming up the Unity module in anticipation of the seven-member crew's arrival. With a launch on Sept. 8, Atlantis is scheduled to dock with the station at 1:12 a.m. CDT Sept. 10.
Now in an orbit with a high point of 228 statute miles and a low point of 222 statute miles, the 67-ton, 143-foot long International Space Station can easily be viewed from the ground under proper lighting conditions. To see when the station is visible, check the human space flight website at:
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The next Mission Control Center status report will be issued following Atlantis' launch on Sept. 8 or as events warrant. For more information, call the Johnson Space Center Newsroom at 281/483-5111.
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