Florida ? Space shuttle Endeavour aimed for landing tonight back at NASA’s spaceport, but rainy and cloudy weather threatened to delay the astronauts’ homecoming.

Endeavour and its crew of six are returning from a bigger and certainly brighter International Space Station. They added a new room and a dome containing seven windows in a highly successful mission that won presidential praise.

LeRoy Cain, chairman of the mission management team, said Saturday there’s about a 50-50 chance — maybe a little better — that the weather will cooperate.

Mission Control will have Edwards Air Force Base in California, the backup site, ready to support a landing as well, just in case Florida doesn’t pan out.

Endeavour has enough power and supplies to remain in orbit until Tuesday.