The TerreStar-1 satellite had a launch mass of 6,910kg
The world's biggest commercial telecommunications satellite has been put in orbit by an Ariane 5 rocket.
The TerreStar-1 platform weighed just shy of seven tonnes at launch.
Built for TerreStar Networks, the spacecraft will provide voice, messaging and data connections to the North American market.
The satellite was so big it was the only passenger on Ariane which routinely carries double payloads from the Kourou spaceport in French Guiana.
The heaviest commercial satellites in the past have been of the order of six-and-a-half-tonnes.
Blast-off was delayed because of stormy weather but eventually took place at 1452 local time (1752 GMT).
The Ariane 5 rocket carrying TerreStar-1 launches
Built by Space Systems/Loral, TerreStar-1 has a huge deployable reflector antenna, measuring 18m across. It was stowed like an umbrella for launch and will be unfurled in the next couple of weeks in a procedure that should take about four hours.
TerreStar-1 is the centrepiece of an integrated space and terrestrial service for which customers will use a smart phone-sized device. This is a step-change from some of the bulky gear normally associated with satellite comms.
"It's the first full-mode terrestrial/satellite handset," TerreStar President Jeff Epstein told BBC News.
The handset is similar in size to everyday smartphones
"It's about the size of a Blackberry 'Curve'. It's very small; everything is internal: there are no external antennas.
"It will work on a terrestrial network as a normal cell phone would, and when you're out of range or the network's down for whatever reason, it will go to the satellite. The whole premise of our business model is that to get wide adoption, you need a handset that is useable, not something that is huge."
In the first instance, it is expected the primary users will be government, emergency responders, rural communities and commercial users.
Wednesday's launch was the third of the year for Ariane.
On its previous outing, the rocket placed in orbit the Herschel and Planck space telescopes. Their combined 1.9bn-euro programme cost made the event the most valuable launch in the history of European space science.
Four more Ariane flights are planned this year.
TerreStar-1 has a huge deployable antenna reflector
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