The second step in a $1.5 billion program to create a mobile broadband communications network spanning the globe for users at sea, in the air and on land roared into space today.

The Zenit rocket launches with Inmarsat 4-F2. Credit: Sea Launch

The Inmarsat 4-F2 satellite lifted off from a floating platform in the equatorial Pacific Ocean at 1407 GMT (9:07 a.m. EST) atop a commercial Sea Launch Zenit 3SL rocket.

The three-stage booster took about 85 minutes to haul the 13,108-pound spacecraft to the desired altitude.

When it enters service from geostationary orbit 22,300 miles above Earth next year, the craft will join the Inmarsat 4-F1 satellite that was successfully launched on Lockheed Martin's Atlas 5 rocket in March from Cape Canaveral, Florida. Together, the two craft will deliver broadband communications to 85 percent of the world.

"Putting almost half-megabit data speeds for people to access globally where terrestrial networks don't go we see as a fundamental service," said Inmarsat CEO Andrew Sukawaty. "It's really about taking the office with you where terrestrial networks don't go economically."

Inmarsat's newest generation of satellites come with the tag line "broadband for a mobile planet." Built in Europe by EADS Astrium, the Inmarsat 4-series spacecraft will provide office-like broadband services such as Internet, email, voice and data-relay using laptop and palm-sized terminals.

"It will transform the way people who are out of reach of other communications access broadband services," said Frank August, Inmarsat's regional director for North America.

The Inmarsat 4-series of satellite also continue the existing lower-data-rate capacity currently offered by the London-headquartered company for maritime, air and emergency services, and enhanced navigation signals for air traffic uses.

"Basically, it is going to expand our services and extend the life of our service to the end of the next decade," Sukawaty said.

An artist's concept shows the Inmarsat 4-series satellite in orbit. Credit: EADS Astrium

The sophisticated satellites transmit over 200 spot beams to deliver strong signals to the small receivers. Each craft has a giant unfurlable antenna reflector stretching 30 by 39 feet.

The new craft are 60 times more powerful and have 20 times more capacity than their predecessors, the Inmarsat 3-series of satellites.

Inmarsat 4-F1 is operated over the equator at 64 degrees East over the Indian Ocean to cover Europe, Africa, the Middle East and Asia. The sister satellite launched today -- Inmarsat 4-F2 -- is scheduled to be placed at 53 degrees West to serve South America, most of North America, the Atlantic Ocean and part of the Pacific Ocean.

Inmarsat has built the F3 spacecraft as a backup for the first two satellites. If not needed as a replacement, the craft could be deployed over the Pacific as the third member of this broadband satellite constellation. Inmarsat has contracted with Atlas 5 for another launch.

Today's liftoff was Sea Launch's fourth flight of 2005 and 18th overall since debuting in 1999.

"All indications are that this was an absolutely outstanding launch. It launched right at the beginning of the launch window, went right down the center of the line, and everything was right on the mark," said Sea Launch president Jim Maser.

The Zenit 3SL rocket uses Ukrainian-made Zenit first and second stages to power the first eight minutes of flight and a Russian-manufactured Block DM-SL upper stage to accelerate the payload to the target altitude for deployment.