LOS ANGELES - Private US spaceflight company SpaceX launched 10 more satellites from California Wednesday morning as part of an ambitious project to build a network of satellite telephone relay stations.

A Falcon 9 rocket blasted off from the Vandenberg Air Force Base at 4:39 local time (1139 GMT), carrying 10 Iridium NEXT satellites for Iridium Communications, an American company providing satellite communications.

The launch went smoothly despite fog obscuring the view of the rocket until after the liftoff.

John Insprucker, principal integration engineer at SpaceX, said during a live webcast that the weather and sea conditions were "fairly rough."

"They are the worst that we've ever had for trying to get a first stage on the droneship," he said.

About 7.5 minutes later, the first stage of the rocket successfully landed on a droneship stationed in the Pacific Ocean.

"Despite challenging weather conditions, Falcon 9 first stage booster landed on 'Just Read the Instructions (droneship),'" SpaceX tweeted.

The satellites were deployed about 56 minutes after the liftoff, with the entire process taking about 15 minutes.

"Successful deployment of 10 @IridiumComm NEXT satellites to low-Earth orbit confirmed," SpaceX tweeted.

Wednesday's mission, called Iridium-7, was conducted to put the seventh set of satellites in space. Altogether, SpaceX will launch 75 satellites for Iridium's next generation global satellite constellation.