The Sea Launch company has returned to flight with a mission to loft a telecoms satellite to serve the Middle East and the Asia-Pacific region.
The firm's Zenit rockets launch from a converted oil platform
The firm's Zenit 3SL rocket lifted off from its converted oil rig platform stationed in the Pacific at 1149 GMT.
The Thuraya 3 satellite separated from the vehicle some 98 minutes later.
The flight was the first for Sea Launch since the catastrophic explosion in January 2007 which destroyed a Zenit and its payload on the pad.
Sea Launch is based in Long Beach, California, but is operated by an international consortium, including the Boeing aerospace company and the Russian spacecraft manufacturer Energia.
It uses a floating platform and a command ship for launches. Both are sailed out of California to the equator at 154 degrees West.
The position, close to the Pacific island of Kiritimati, means the Zenit rocket can take full advantage of the Earth's rotational speed and launch more mass for less effort, compared with the world's major land-based spaceports.
Tuesday's successful mission was the 25th for Sea Launch.
"It feels good to be back," said company president Robert Peckham.
Sea Launch is seen as an important competitor for the European launch services company Arianespace, which, in the absence of the Pacific Ocean system, lofted 80% of the world's commercial payloads in 2007.