CAPE CANAVERAL, Fla. -- Discoverys astronauts mounted a $273 million truss on the International Space Station Saturday despite a short circuit that temporarily knocked out a computerized television system considered key to the construction work.
The Z1 truss assembly is seen here after it is attached to the station on Saturday, while the shuttle's robot arm moves away. Image from NASA TV.
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Wielding the shuttles 50-foot-long (13-meter-long) robot arm, Japanese mission specialist Koichi Wakata lifted the nine-ton metal truss from a shuttle cargo bay cradle and then put it in place atop the 13-story outpost.
"Ok, we look like weve got a good capture," shuttle pilot Pam Melroy said after the new station segment was firmed latched into place.
"We copy and see the same from here," astronaut Ellen Ochoa replied from NASAs Mission Control Center in Houston, Texas. "Good work."The job, however, came to a screeching halt before it could really start.
Just as Wakata was limbering up the robot arm, an electrical short crashed a computerized TV system crucial to positioning the cube-shaped truss atop the station.
"What timing, huh?" shuttle skipper Brian Duffy said. "Unbelievable."
With the towering station blocking the view out of Discoverys flight deck windows, the so-called "space vision system" serves as a set of "electronic eyes" at the station construction site.
~Fast repairs
Consequently, a two-hour scramble ensued. And ultimately, the astronauts plugged a back-up into an alternate power source, enabling Wakata to carry out the most complex station assembly chore to date.
"They dont call him 'The Man' for nothing," Melroy said.
A close up view shows Unity (left) securely attached to the Z-1 truss. Image from NASA TV.
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Perched atop the outpost now is the stations Z-1 truss, the first part of what eventually will be a 10-piece metal backbone than spans an area as long as a football field.
Weighing in at 18,400 pounds (8,280 kilograms), the truss houses four stabilizing gyroscopes and a dish-shaped communications antenna.
The domed-shaped gyroscopes are designed to reduce the amount fuel needed to keep the station properly positioned in orbit.
The antenna -- which will be assembled and deployed during a spacewalk Monday -- will be used to beam television and voice communications between the outpost and ground controllers.
Now sitting atop an American docking module dubbed "Unity," the truss also will serve as a temporary mounting platform for power-producing solar arrays that are to be launched to the station aboard shuttle Endeavour in late November.
~Troubled vision
Still unexplained, the short circuit shut down the space vision system, a cargo bay camera and a device that enables data to be transmitted between the shuttle and the international outpost.
The sophisticated vision system -- which comprises a laptop computer, cargo bay cameras and dice-like targets mounted on all station components -- was considered particularly crucial to the construction work Saturday.
A NASA animation based on data radioed from Discovery shows the Z1 truss (module sticking out on the right side) attached to the rest of the space station. Image from NASA TV.
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Designed and developed by the Canadian Space Agency, it measures the size of black dots on the targets to determine the relative position and exact orientation of both the station and components being attached to it.
The job at hand, meanwhile, called for Wakata to mount the boxy truss to a berthing port on the far side of the station -- a site that cant be seen from the shuttles flight deck.
The astronauts, consequently, spent a little more than two hours hooking a spare vision system computer to an alternate power source, restoring Wakatas electronic eyes in the process.
A back-up system was pressed into service to get data flowing between the shuttle and the station, but the cargo bay camera could not be fixed. So astronaut Michael Lopez-Alegria was sent into the Unity module to watch the truss installation through a small window.
Linking the truss to the Unity module is a computer-controlled berthing mechanism equipped with a complex set of four interlocking latches and 16 motor-driven bolts.
Working with a laptop computer on the shuttles flight deck, Melroy sent commands that activated the latches and the drove the bolts, forming an airtight seal between the truss and the Unity module, which serves as a pressurized passageway to other parts of the outpost.
"Its a methodical, slow process, but one thats required to make a complete and final seal," said NASA flight commentator Kyle Herring.
Thats important because Discoverys crew plans to enter a small pressure dome within the truss to help wire it up to the station.
~Spacewalks ahead
The truss installation set the stage for the first of four consecutive days of spacewalking construction work at the outpost.
Astronauts Leroy Chiao and Bill McArthur will set out on the first foray at 10:32 a.m. Eastern Daylight Time (1432 GMT) Sunday. The two astronauts will route electrical cables between the truss and the station and then deploy the outposts main communication antenna.
The astronauts other big construction job -- putting a new shuttle docking port in place at the station -- will be carried out by Wakata Monday with an assist from spacewalkers Lopez-Alegria and Jeff Wisoff.
Voltage converters that will carry electricity generated by the stations soon-to-be-delivered solar arrays will be set up by Chiao and McArthur Tuesday during the third spacewalk.
The highlight of the mission, however, is expected to come Wednesday as Wisoff and Lopez Alegria test-fly jet backpacks designed to enable spacewalkers to maneuver back to the station if standard safety tethers snap, casting them adrift in space.
The jetpack test-flights are considered crucial because NASA still faces an additional 155 spacewalks to complete station assembly between now and April 2006.
The crew also will spend a day inside the station, delivering supplies for the outposts first full-time tenants, who are due to take up residence at the station in early November.
As it stands now, Discovery and its crew are scheduled to depart the station next Friday, heading out on a two-day trip back to Earth.
NASAs 100th shuttle flight is slated to wrap up with a 2:10 p.m. EDT (1810 GMT) Oct. 22 landing here at Kennedy Space Center.
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