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. Last Updated: 07/27/2016

Celestial Embrace to Pave Way For International Space Station

WASHINGTON -- Two decades after Russian and U.S. crews joined their spacecraft briefly for a symbolic handshake, the world's major spacefaring powers are preparing for another celestial embrace with much higher stakes.

If all goes well, the U.S. shuttle Atlantis will lift off late Friday afternoon from Kennedy Space Center in Florida, heading for a delicate docking with the Russian Mir space station 368 kilometers above eastern Russia on Monday.

Technicians worked to fix a leaking helium gas line on the shuttle, a problem managers said could probably be resolved by Friday. But predicted thunderstorms also threatened to postpone the scheduled liftoff.

The mission, which happens to be the 100th U.S. human spaceflight, is the first of a series of trial runs for the most challenging space assembly project ever attempted -- the construction of an international space station. The docking missions also are aimed at demonstrating that such an ambitious project can be carried out by two nations that once were bitter rivals and now are struggling to keep their space programs aloft.

"In 10 or 15 years from now as we look back, I would be surprised if we did not see this as a major milestone in the evolution of human spaceflight,'' Tommy Holloway, the NASA manager of the shuttle-Mir docking missions, said.

While each craft zips around Earth at 28,000 kph, shuttle commander Robert "Hoot'' Gibson will slowly maneuver Atlantis toward the Mir's 1.5-meter-wide docking port.

Compared to the docking of the small Soyuz and Apollo capsules in July 1975, this will be like two 100-ton gorillas grappling each other. Yet, near the end, as the shuttle draws within a few feet of the Mir, Gibson must keep Atlantis' approach accurate to 7.5 centimeters.

The primary goal of this first mission is to replace the crew aboard Mir. Atlantis will retrieve U.S. astronaut Norman Thagard -- who has been aboard Mir since March and recently set an American space endurance record -- and his two Russian colleagues.