By Kathy Sawyer
Washington Post Staff Writer
Monday, December 7, 1998; Page A01

HOUSTON, Dec. 6—The crew of space shuttle Endeavour late today swept down on a massive Russian module waiting in orbit and, with the caution of a surgical team, grabbed and mated it to a U.S. sister pod, beginning a monumental five-year construction job in space.

With the successful marriage of the two modules 240 miles above the southern Pacific at 9:07 p.m. EST, the United States and Russia linked their fates physically in one of the most complex undertakings ever attempted -- the assembly of the first international space station in orbit.

The feat required precision flying under unusually difficult conditions by Endeavour commander Robert Cabana and delicate maneuvering by flight engineer Nancy Currie, an Army helicopter pilot who used the shuttle's robot arm to pluck the Russian Zarya out of space.

"A lot of people down here are exhaling," said Chris Hadfield from Mission Control at NASA's Johnson Space Center after the precision grapple.

Because the 15-by-33-foot U.S. module called Unity blocked their view out the windows, the astronauts had to conduct the rendezvous and the grapple "in the blind," relying solely on cameras and a computerized vision system essentially based on polka dots.

The U.S.-Russian crew of six was, in effect, laying the foundation for a planned $63 billion facility, which is supposed to grow over the years in erector-set fashion into a laboratory, dorm and depot complex with the habitable volume of two 747 jumbo jets and a wingspan longer than a football field.

Because the operation was so critical to the future of human space flight and the investments of 16 spacefaring nations, it was carried out in exaggerated slow motion. This is necessary for controlling massive objects in space which, although they are weightless, still have momentum and must be moved with caution to keep them under control and avoid serious damage.

After Zarya had been grappled, Cabana confirmed suspicions that two antennas on the module had failed to deploy, part of a manual backup system for rendezvous operations. But officials said the failure would have no serious impact.

The action started at about 2:50 p.m. EST, when Cabana told Mission Control he had spotted Zarya, then at a distance of 58 miles. As the orbiter approached Zarya from below, at about 4:15 p.m. EST, with both vehicles traveling at about 17,000 mph, Russian ground controllers commanded their craft to point its aft toward the ground and its docking port up. The need for a direct line of sight between the Russian controllers and Zarya made the rendezvous approach unusually difficult, officials said.

Unlike the usual rendezvous approaches from the side or below, Cabana had to make his final approach from above Zarya. After Endeavour passed some 600 feet beneath the Russian module, Cabana and pilot Rick Sturckow began an upside-down swan dive that carried them up and over Zarya in a slow back-flip, pitching over the Russian module at a distance of about 250 feet. Cabana then slowly flew Endeavour straight down to within 10 feet of Zarya.

This strategy required Cabana to counteract the force of gravity, pulling the orbiter toward Earth while contending with the distracting background of the planet's cloud-strewn blue surface racing past below. Once Zarya was within about 70 feet of Endeavour, the Unity module rose three stories out of the orbiter cargo bay, blocking the crew's direct view of the Russian module, except for its solar power wings.

Cabana and Currie then relied on the new Canadian Space Vision System, in which a computer processor uses TV cameras to determine distances and angles based on black dots sewn on at precise points to the protective fabric covering the hulls of the space station components. The processor created a computer graphic that overlayed the crew's television view of the modules, providing visual cues to their exact positions.

Currie used the arm to grab a special fixture on Zarya's docking port to then gradually "stairstep" the module to higher positions and finally park Zarya just inches above Unity's upper mating port. At 21 tons, Zarya was by several tons the most massive object ever hefted by the orbiter arm.

The two craft resembled kissing fish as the robot arm pulled Zarya toward Unity, and lighting conditions improved as the spacecraft flying in tandem moved into sunlight, a condition necessary for the difficult maneuver.

Once Zarya was precisely positioned, Currie put the arm in "limp mode" while Cabana fired jets on the shuttle, driving Unity and Zarya together.

When the mating was confirmed, cheers erupted among mission controllers in Houston and Moscow. But some tense minutes followed when telemetry indicated a misalignment at the junction of the two modules, where a system of interlocking rings and capture latches were supposed to pull together and lock the two crafts. After analysis, the ground and flight crews agreed that the culprit was the robot arm, which even in limp mode continued to exert pressure on one side of Zarya. Currie was directed to release the arm's grip earlier than planned, and astronaut Jerry Ross reported that the misalignment immediately corrected itself. The mating process was completed at about 9:50 p.m.

The two elements, now seven stories tall, will not become a single functioning space station until Ross and crew member Jim Newman take a series of spacewalks beginning Monday, during which they will scramble over the massive structures to hook up some 40 cables and sockets that will carry electrical power and data throughout the complex. More than 160 such spacewalks will be required over at least five years of construction work on the orbital facility.

On Thursday, the crew plans to enter the newly joined complex and test the computer, communications and television systems, and remove hundreds of bolts inside Zarya that were required to secure it for its Nov. 20 launch from central Asia.

Unity is a squat, six-sided pressurized cylinder that resembles a diving bell. It is to serve as a hub for several future space station components and a passageway for crew members moving from the shuttle into the space station. At either end of Unity is an airlock, with an exterior docking system of rings with latches that snap closed and capture other station elements and provide pressure-tight seals throughout the resulting combined structures.