Zarya remains in excellent condition overall with only a few minor mechanical issues under analysis that are not expected to pose any problems for the planned operations of the International Space Station. For one of the problems -- a potential glitch with the energy storage and discharging capability of one of six batteries housed in the Zarya module - flight controllers are planning to carry replacement parts aboard Endeavour that could be installed by the shuttle crew. The battery is still usable with the glitch, and even without any repairs performed, the problem would not be expected to have an impact on Endeavour's mission or following station operations, although it would decrease the amount of backup energy and battery systems available.
Station mission managers have decided to load two small replacement electronics boxes for the battery system, a current converter unit and a storage battery current regulator unit (referred to by the Russian acronym PTAB), aboard Endeavour along with associated cabling. A decision on whether the crew will be asked to install any of the equipment during the flight has not been made.
Tests of the battery system during the weekend have led Russian flight controllers to suspect the problem may most likely be within the storage battery current regulator unit (PTAB). Endeavour Mission Specialist Sergei Krikalev, a Russian cosmonaut, has performed a similar repair on equipment aboard the Mir Space Station.
Flight controllers also plan to request that Endeavour's crew use television cameras to view the antennas on Zarya associated with the Telerobotically Operated, or TORU, manual docking system. Recent signal-strength testing has indicated these antenna may be fully deployed, although the deployment cannot be confirmed from other data. The crew will inspect the antennas during a standard television survey of Unity and Zarya planned on Day 4 of Endeavour's flight. Mission Specialists Jerry Ross and Jim Newman are planned to traverse near the area of one of the TORU antennas during the third spacewalk planned for STS-88, as they move to the far end of Zarya to install a handrail. No spacewalking activities involving the antenna are planned, however.
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 in an orbit of 250 by 240 statute miles.