Endeavour's astronauts continued the assembly of the International Space Station late Sunday, mating the Russian-built Zarya control module with the U.S.-built Unity connecting module in the shuttle's cargo bay following a flawless rendezvous and grapple of Zarya.
Using the shuttle's 50-foot-long robot arm, astronaut Nancy Currie plucked Zarya out of orbit at 5:47 p.m. Central time Sunday, more than 16 days after it was launched on a Russian Proton rocket from the Baikonur Cosmodrome in Kazakstan as the first component of the new station. After slowly and carefully aligning Zarya's docking mechanism with a comparable mechanism on Unity's Pressurized Mating Adapter-1, Commander Bob Cabana fired Endeavour's downward jets at 8:07 p.m. to drive the two large modules together.
Initial attempts to firmly latch Zarya and Unity together while the shuttle's robot arm was attached to Zarya's grapple fixture were unsuccessful. But after Currie ungrappled the module, hooks and latches between Zarya and Unity engaged at 8:48 p.m., forming a tightly sealed, 35-ton, 76-foot-tall structure rising from Endeavour's payload bay, the size of a seven-story building.
Currie used the robot arm cameras to conduct a detailed survey of Zarya, focusing on two antennas belonging to the Telerobtically Operated Rendezvous System (TORU), which failed to deploy following launch on Nov. 20. Flight controllers concluded that the pyrotechnic pins holding the antennas in place actually fired, but the antennas did not unfurl as planned. The antennas, which are part of a backup navigational aid system, are emitting signal strength in their current position and pose no problem for future station operations. But flight controllers are considering having astronaut Jerry Ross conduct a more thorough survey of the antennas while affixed to the end of the shuttle's robot arm during the first space walk he and Jim Newman will conduct Monday night. Mission managers have not decided whether Ross and Newman will be called upon to manually deploy the antennas on a future space walk.
The first space walk, scheduled to begin about 4:30 p.m. Central time today, may begin earlier if Ross and Newman are ready to depressurize Endeavour's external airlock ahead of schedule. During the planned 6 ½-hour excursion, Ross and Newman will hook up electrical cables and connectors between Zarya and Unity, enabling power to flow into the U.S. component for the first time. That will allow Unity's avionics, computers and heaters to be activated to set the stage for the ultimate shifting of command and control and the origination of the power for the International Space Station from the Russian components to the U.S components once the American-built Destiny laboratory is joined to the station in February 2000.
Russian and American flight controllers also are continuing discussions on the possible swap out of a suspect component for one of Zarya's six batteries. The battery is not discharging properly in its automatic mode. A replacement unit is available for installation if mission managers approve the plan. The battery is operational and poses no threat to future station operations even if left in its current configuration.
The astronauts are scheduled to begin an eight-hour sleep period at 3:36 a.m. Central time and will be awakened at 11:36 a.m. to prepare for the first space walk of the flight.
Endeavour and the International Space Station are orbiting the Earth at an altitude of 240 statute miles with all systems in excellent shape.
The next STS-88 status report is scheduled to be issued after the astronauts are awakened for their fifth day in orbit.
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