By Jeff Franks

HOUSTON (Reuters) - The space shuttle Atlantis winged toward a rendezvous with theInternational Space Station on Sunday, lugging the heaviest payload ever for the orbital outpost and troubled only by a small tear in a heat-protecting thermal blanket.

Atlantis was scheduled to link up with the station at 3:38 p.m. EDT (1938 GMT) for a week-long stay in which the shuttle crew will install electricity-generating solar panels on the half-finished station.

On Saturday night, Atlantis astronauts tested tools for the planned rendezvous more than 200 miles above the earth and fired the ship’s engines to speed it on its way after it launched from Florida on Friday.

The shuttle is carrying a 45-foot-(14-metre) long, 35,678-pound (16,183 kg) aluminum structure that will become part of the station’s structural backbone and includes the solar panels. Its crew members are scheduled to perform three spacewalks to install the new parts and retract an old solar array.

Among the seven Atlantis astronauts is Clayton Anderson, of Ashland, Nebraska, who will join Russian cosmonauts Fyodor Yurchikhin and Oleg Kotov on the station, replacing Sunita Williams.

Williams, after six months on the $100 billion outpost that is a joint project of 16 nations, will catch a ride home on Atlantis.

NASA plans to fly 12 more missions to complete the station. It also wants to make two flights to store spare parts and service the Hubble Space Telescope a final time before its three’shuttle fleet is retired in 2010.

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