Inmarsat-4 F2, one of the largest and most powerful communications satellites ever built, has succesfully launched from a floating pad in the Pacific.
The launch, from a converted oil platform, went smoothly
The six-tonne UK-built craft was carried aloft by a Zenit-3SL rocket at approximately 1407 GMT on Tuesday.
The launch had twice been postponed after a software glitch stopped the countdown sequence on Saturday.
Inmarsat-4 F2 is designed to improve broadband and 3G communications, principally in the Americas.
It is the second in a planned two-satellite constellation.
The first spacecraft launched in March covers most of Europe, Africa, the Middle East, Asia and the Indian Ocean.
The new satellite will improve and extend communications across South America, most of North America, the Atlantic Ocean and part of the Pacific Ocean.
The two satellites will support the London-based Inmarsat company's global broadband network, BGan.
Their onboard technology is designed to allow people to set up virtual offices anywhere around the world via high-speed broadband connections and new 3G phone technology.
Those set to benefit include business travellers, disaster relief workers and journalists.
Andrew Sukawaty, CEO and chairman of Inmarsat, said: "The successful launch of the second I-4 satellite means that Inmarsat now has the world's most sophisticated commercial network for mobile voice and data services.
The craft will deliver broadband from the Arctic to the Antarctic
"It will support an unprecedented evolution of our services - more than doubling the bandwidth available to our mobile users."
The spacecraft, each the size of a London bus, should continue functioning for about 15 years. They were built largely at the EADS-Astrium facilities in Stevenage and Portsmouth, UK.
The Inmarsat-4 F2 was launched from waters close to Kiritimati (Christmas Island) on the equator.
It used the innovative Sea Launch system, which employs a converted oil drilling platform as a launch pad. The pad is moved into position from its California base.
Sea Launch is a joint venture between American, Russian, Ukrainian and Norwegian companies.