Weather improves for commercial space station delivery (Update)

NASA's spirits soared Sunday as weather forecasters offered significantly better odds of launching a rocket with much-needed supplies to the International Space Station.

With two hours remaining in the countdown, forecasters announced that the wind that had spoiled previous launch attempts finally had eased, and the sky was clear save for a few wispy clouds.

It was the fourth launch attempt for the unmanned Atlas rocket, loaded with food, experiments and Christmas presents for the astronauts at the International Space Station.

"Back in the saddle," rocket maker United Launch Alliance's president, Tory Bruno, said in a tweet.

If successful, this would be the first U.S. shipment to the space station since spring. Launch failures have sidelined both of NASA's commercial suppliers; United Launch Alliance's trusty Atlas V was called into service to get the supply chain moving again.

Awaiting a 4:44 p.m. liftoff, the rocket holds 7,400 pounds of supplies, all packed into a capsule named Cygnus after the swan constellation.

Shipper Orbital ATK shifted the Cygnus to the Atlas because its own rocket, the Antares, has been grounded since October 2014.

With six astronauts on board, the space station has dipped below NASA's desired six-month food supply. So lots of groceries are going up.

SpaceX, NASA's other commercial supplier, made the last successful supply run from the U.S. in April. Its next cargo ship, launched two months later, ended up in the Atlantic following a failure of its Falcon rocket.

The California-based SpaceX aims to resume deliveries next month, while Virginia's Orbital hopes to get its Antares flying again in May, 1 ½ years after a devastating launch explosion. In the meantime, Orbital is counting on this Atlas and another one to fill the gap. Russia, which also lost a shipment earlier this year, has another supply run coming up in two weeks.

United Launch Alliance builds and flies the powerful Atlas V, a workhorse normally used to hoist satellites for the Air Force and others. This is its first station mission. Boeing plans to use the Atlas V to launch its commercial crew spacecraft for NASA, the Starliner, as early as 2017.

NASA hired out station supply and crew missions to industry, for billions of dollars, as its 30-year shuttle program wound down.

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