STS-92 Day 4 Highlights

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On Saturday, October 14, 2000, 6:00 a.m. CDT, STS-92 MCC Status Report # 6 reports:

Discovery^Òs crew is set to install the first of two major components that it carried to the Space Station today ^Ö a unique piece of hardware called the Z1 truss. The truss is an exterior framework that houses gyroscopes and communications equipment and later will serve as a mounting platform for large solar arrays that will provide power to the International Space Station.

Earlier this morning, space station flight controllers in Houston successfully activated and checked out controllers and power sources for Unity^Òs common berthing mechanism, preparing it for the Z1 installation. Discovery^Òs robot arm will be powered up at 7:37 a.m. by NASDA astronaut Koichi Wakata and Mission Specialist Mike Lopez-Alegria. Wakata will maneuver the arm to the Z1 truss in Discovery^Òs payload bay, grappling the box-like frame about 8:20 a.m.

A series of capture latches that secures the truss in place will be commanded open and Wakata will gently raise the Z1 out of the payload bay. With the truss firmly in its grip, the arm will be maneuvered to a position called low hover and will remain during a final inspection to ensure that all seals and petals on the common berthing mechanism are properly aligned for the final installation. Commander Brian Duffy will maneuver Discovery into the proper orientation for installation as the Z1 is moved to its capture position. A series of four ^Óready to latch^Ô indicators are the signal for Discovery^Òs crew to issue the final capture command, and the Z1 truss should be attached to the Space Station shortly after 10 a.m. today.

Using a laptop computer, Pilot Pam Melroy will command 16 bolts to tighten in a four-stage process to secure the Z1 truss to the Unity module, as Wakata releases the Shuttle^Òs robot arm and moves it back to its cradled position alongside the payload bay. Final connections and outfitting work for the Z1 truss will be accomplished by space-walking astronauts Bill McArthur, Leroy Chiao, Jeff Wisoff and Mike Lopez-Alegria. Sunday, during the first of four scheduled spacewalks for this flight, McArthur and Chiao will connect a series of power cables, an S-band communications assembly, install a Space to Ground Antenna and boom assembly and install an EVA tool stowage box on the port side of the structure.

With the Z1 installation complete, the astronauts will enter the Zarya module to transfer equipment and supplies for the first resident crew expected to arrive later this month. McArthur and Chiao will configure Discovery^Òs middeck in preparation for Sunday^Òs spacewalk, staging some of the tools, tether and hardware they will use during their planned 6½-hour EVA.

The next Mission Control Center status report will be issued at 7 p.m. CDT or as events warrant.

On Saturday, October 14, 2000, 8:00 p.m. CDT, STS-92 MCC Status Report # 7 reports:

The crew of Discovery added nine tons of critical equipment to the International Space Station today, attaching a framework that holds motion control gyroscopes and communications equipment and that will serve as a support for a giant set of solar arrays to be launched on the next Space Shuttle flight.

Japanese Astronaut Koichi Wakata, at controls in the shuttle cockpit, deftly maneuvered Discovery's robotic arm to lift the framework, called the Z1 truss, out of the shuttle's payload bay and berth it to a port on the station's Unity connecting module. The berthing was the first time the U.S.-developed attachment system has been used in orbit, and the equipment worked flawlessly. Over the course of the station's future assembly, similar attachment systems will be used over 100 times. Astronaut Mike Lopez-Alegria, looking out of the berthing port's hatch window in Unity, provided Wakata with visual cues as to the framework's alignment.

The berthing occurred about two hours behind schedule due to a short-circuit aboard the shuttle early in the crew's day that cut off power to some equipment Wakata would need. The short cut power to three pieces of equipment: an Orbiter Interface Unit that provides data and commanding from the shuttle to station systems; an Orbiter Space Vision System that provides a computerized alignment aid for operating the robotic arm; and a television camera located at the bottom, or keel, of the payload bay that faces upward to provide a supplementary visual cue for maneuvering the truss structure. Flight controllers and the crew quickly developed a plan to use backup equipment and alternate power to regain all functions except the keel camera, and Wakata began lifting the truss from the shuttle bay about 2 hours and 15 minutes later than originally planned.

The backup arrangement worked perfectly. The electrical bus that experienced the short will remain powered off and will have no impact on the rest of the mission's activities. Wakata latched the truss to the station at 1:20 p.m. as the complex flew 240 statute miles above southern Russia.

Because activities were behind schedule following the morning workaround, flight controllers opted to defer the transfer of some gear from the station's Unity module to the Zarya module until the crew next enters the station, planned for day nine of the mission. In Unity, Pilot Pam Melroy and crewmate Jeff Wisoff opened the hatch where the new truss was attached and, inside a pressurized dome, installed grounding connections between the framework and the station. Afterward, the crew exited the station, and, at 5:57 p.m. CDT, Lopez-Alegria and Commander Brian Duffy sealed the station's outermost hatch.

Duffy and Melroy then lowered Discovery's cabin pressure in preparation for a space walk by astronauts Leroy Chiao and Bill McArthur planned to begin at 9:32 a.m. Sunday. Reducing the cabin pressure from a sea-level pressure of 14.7 pounds per square inch (psi) to a pressure of about 10.2 psi is part of a protocol that purges nitrogen from the space walker's body to prevent decompression sickness. Chiao and McArthur spent the last couple of hours of their day preparing equipment in the shuttle's lower deck and airlock for tomorrow's venture outside the cabin. During the space walking construction work, the first of four space walks planned during Discovery's mission, the two will connect electrical and computer data cables between the newly attached truss and Unity and deploy two communications antennas from the truss.

The crew begins a sleep period at 9:17 p.m. today and will awaken at 5:17 a.m. Sunday to begin preparations for the six and a half-hour space walk. The next Mission Control Center status report will be issued at 6 a.m. CDT or as events warrant.

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