After watching thunderstorms and rain showers near NASA's Kennedy Space Center in Florida, NASA's Mission Control cleared the shuttle Endeavour to begin its decent to Earth on Friday.
The shuttle's seven astronauts were scheduled to touch down at 10:47 a.m., EDT 1447 GMT.
As day broke at the Florida shuttleport, rain showers formed off the Atlantic coast too close to the long Kennedy runway for a safe return. But the conditions improved as forecasters predicted.
"Good news," Mission Control told Endeavour commander Mark Polanski. "You are 'go' for the de-orbit burn."
"You are a steely-eyed hero," said Polanski. "The flight crew is all strapped in."
The shuttle crew includes Koichi Wakata, Japan's first long duration astronaut. Friday was his 138th day in space.
Endeavour lifted off for the international space station on July 15 with last piece of Japan's Kibo science laboratory.
The shuttle crew equipped Kibo with a new external science platform and replaced the batteries in the station's oldest solar power module.
Also aboard Endeavour were pilot Doug Hurley, Julie Payette of Canada, Chris Cassidy, Tom Marshburn and Dave Wolf.
The start of their long mission was delayed a month by a siege of thunder storms at Kennedy and an elusive hydrogen leak in the shuttle's fuel tank ventilation system.
