(Updates throughout, changes dateline previous HOUSTON)

By Irene Klotz

CAPE CANAVERAL, Fla., March 19 (Reuters) - The ubiquitous voice of Mission Control fell silent for much of Wednesday as the shuttle Endeavour astronauts took time off midway through what NASA expects to be its longest visit to the International Space Station.

The seven men relaxed in private with their space station hosts, with television cameras focused mostly on the outside of the station and the new 12-foot (3.7-metre) robot anchored atop the U.S. Destiny laboratory.

Assembling the mechanical maintenance man and delivering a storage room for Japan's upcoming Kibo laboratory complex were the primary goals of NASA's 122nd shuttle mission. The agency has just 11 flights remaining before its three-ship fleet is retired.

Most of the work was accomplished during three spacewalks, with two more outings remaining for station maintenance and to test a technique for fixing the shuttle's heat shield.

NASA has been developing inspection and repair procedures since losing shuttle Columbia and its seven-member crew in 2003 due to undetected damage to one of its wings.

NASA wants the demonstration complete before dispatching a shuttle crew to service the Hubble Space Telescope, which is too far away from the station for it to shelter the crew should their ship be critically damaged.

NASA plans to have a second shuttle standing by at the launch pad ready to mount a rescue mission if needed. In-flight repairs would be another option if the damage is not too severe.

Endeavour arrived at the station on March 12 and is due back at the Kennedy Space Center in Florida on March 26.

NASA's next mission, targeted for launch in May, will be to deliver the main part of Japan's laboratory. (Editing by Todd Eastham)

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