This story was updated at 9:17 p.m. EST.
Space shuttle Endeavour and its crew of six astronauts are headed home, wrapping up a two-week mission that left the International Space Station nearly complete and added a breathtaking set of windows to the orbiting lab.
Despite a gloomy weather forecast of rain and clouds, conditions cleared enough on the ground to allow Endeavour to fire its rocket engines to leave orbit for a planned landing at 10:20 p.m. EST (0320 Monday GMT) tonight at NASA's Kennedy Space Center in Cape Canaveral, Fla.
Endeavour is returning after delivering a panoramic bay window and new room to the International Space Station.
"We're looking forward to today," shuttle commander George Zamka radioed Mission Control.
Rain and low clouds were expected near Endeavour's runway in Florida, but both concerns evaporated as landing time neared. NASA had also activated Endeavour's backup runway at the Edwards Air Force Base in California, just in case it would be needed.
Next Stop: Earth
Endeavour is returning to Earth to cap a 14-day mission to the International Space Station, where it delivered a phenomenal lookout dome and brand-new Tranquility module orbiting laboratory.
"Thanks for giving station a window to the world!" Mission Control told the shuttle astronauts in their morning mail. "Now's the time to prepare Endeavour to 'bring home the gold!'"
The shuttle flight occurred at the same time as the 2010 Winter Olympics in Vancouver, Canada. The astronauts held their own impromptu Olympics in spaceto mark the sporting events.
The Tranquility module is nearly 24 feet (7 meters) long and about the size of a small bus.
It will serve as the space station's life support systems hub, robotic arm controls workstation and gymnasium. NASA named it after the historic Apollo 11 lunar base and even hung a plaque with some moon rock bits from that mission inside after it was opened.
The new lookout dome is a seven-window observation deck that is giving space station astronauts stunning panoramic views of Earth and space. Called the Cupola, the lookout features six windows arranged around a huge central portal that is 31 inches (80 cm) wide; the largest space window ever built.
The two new additions were built for NASA by the European Space Agency and together cost nearly $409 million. It took three spacewalks and some tricky robotic arm work to fully install them at the station.
The delivery of Tranquility and its observation deck to the $100 billion space station leaves it 98 percent complete after more than 11 years of orbital construction by 16 countries.
NASA plans to launch four more shuttle missions after Endeavour's current mission to complete construction of the space station. The agency's three aging space shuttles are due to retire in the fall of this year.
Station computer glitches
While Endeavour's crew prepared for landing, the five astronauts aboard the International Space Station 'spent what was expected to be a day off with unexpected computer failures.
The space station's three main command and control computers repeatedly switched between their primary, backup and standby units. The glitch occurred four times and briefly knocked out space station communications with Mission Control on Earth.
The glitch did not affect the space station's life support systems and posed no risk to crew safety, NASA officials said.
NASA engineers believe the fault may lie software commands associated with the station's European Columbus lab.
Meanwhile, the weather in Florida has also dealt a minor blow to NASA's next space shuttle mission — the launch of Discovery on April 5.
Unusually cold weather has repeatedly delayed Discovery's move from its hangar to the cavernous Vehicle Assembly Building at the Kennedy Space Center, where it will be attached to its fuel tank and twin solid rocket boosters.
NASA hoped to move Discovery early Monday, but has now delayed the short trip to no earlier than Tuesday so shuttle technicians can prepare to deal with the bad weather coming their way, NASA officials said.
SPACE.com is providing complete coverage of Endeavour's STS-130 mission to the International Space Station with Managing Editor Tariq Malik and Staff Writer Clara Moskowitz based in New York. Click here for shuttle mission updates and a link to NASA TV. Live landing coverage begins at 6:30 p.m. ET.