Flight controllers in Moscow continued to monitor the health of systems aboard the first component of the International Space Station as it passed within range of ground stations in Russia today, performing a standard check of two command relay electronics boxes and of the fire detection and suppression system.
The checks of the command relay equipment, technically called multiplexers/demultiplexers, found both in good condition. The two devices make up part of the Zarya module's command and data handling system and provide an interface with computers for control of the International Space Station's power system, environmental system, guidance and navigation system and sensors. For the checks, one of the devices was turned on and operated for about three minutes while a second was turned on and will be left operating through the arrival of Endeavour.
System experts in Moscow and in Houston also are continuing to evaluate several minor systems problems that have been noted on the spacecraft, none of which are anticipated to have any effect on the planned space station operations. The systems issues included an indication of high humidity onboard Zarya from an air monitoring sensor; difficulties with charging and discharging equipment associated with one of the module's six batteries; and a possible problem with the deployment of a TORU manual docking system antenna on Zarya's exterior.
Flight controllers have determined that the indication of high humidity on Zarya was due to a problem in ground software and was an errant indication. In addition, checks of all systems that contain fluid on the module have indicated there has been no apparent leakage. Engineers are working to correct the ground software responsible for the errant indication.
Indications and tests of one of the six batteries onboard have shown that the battery appears to be operating but that electronics equipment associated with it may not be functioning properly. Tests of the battery have verified that it is capable of charging and discharging normally and further evaluations of the situation are continuing. The possibility of carrying replacement equipment aboard Endeavour also is being evaluated. Regardless of the possible problem with the battery's associated equipment, backup procedures may be available that allow the battery to be used, and all planned station operations could be performed on five batteries only if that were necessary. The six batteries aboard Zarya store energy gathered by the twin solar arrays to be used during the orbital night.
Indications from the TORU antennae show that the antennae may not have deployed properly. Further tests of signal strength from the system over the next few days are hoped to provide more information on whether or not the antennae have deployed. The TORU system is a manually operated docking system that serves as a backup for the Kurs automated docking system, which is the primary docking system to be used for the arrival of the Service Module in summer 1999.
During times when Zarya is not actively performing systems checks or other operations, it is put into a slow spin to conserve fuel and maintain moderate temperatures on the spacecraft. Zarya is circling Earth once every 92 minutes. Zarya is in an orbit of 251 by 239 statute miles circling the Earth every 92 minutes.
The next ISS status report is planned for Friday, or as developments warrant.
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