The Proton launched from the Baikonur Cosmodrome
A Russian Proton Breeze M rocket has successfully launched one of the biggest commercial satellites ever built - the Inmarsat-4 (I4-F3).
The telecommunications spacecraft was released by the Proton at 0746 GMT, after a flight of more than nine hours.
It was the rocket's first outing since an upper-stage failure in March left a US coms platform at a useless altitude.
The I4-F3, operated by the UK-based Inmarsat company, will complete the firm's satellite broadband network.
The latest spacecraft joins two others of the same design that are already in orbit. The new satellite will be positioned over the Americas at 98 degrees West to give Inmarsat global coverage.
The company's network delivers high-speed (up to half a megabit) mobile internet and phone services to users on land, at sea and in the air.
The I4s are immense. The main body is 7m high and incorporates a 9m-wide antenna reflector that is unfurled in space like a fan.
"Each is almost the size of a double-decker bus, weighs six tonnes, and has a solar wingspan the length of a football pitch," said Andrew Sukawaty, CEO and chairman of Inmarsat.
It will take about a month to get the I4-F3 ready for service
"Each I4 is 60 times more powerful and has 16 times the capacity of an Inmarsat-3 satellite."
The Proton Breeze M, operated by International Launch Services, left the Baikonur Cosmodrome in Kazakhstan at 2243 GMT, Monday.
The 58m-high, 700-tonne vehicle was making its return to flight after stranding the US AMC-14 satellite well below its intended operational orbit.
A review board determined that a pipe rupture in the Breeze M upper-stage caused the booster to shut down early, and the rocket's manufacturer - the Khrunichev Space Centre - was ordered to make modifications.
Protons have been launching commercial satellites since 1996, but they have a much deeper governmental heritage going back to the 1960s.
The vehicles have despatched science missions to the planets. They have also launched key components of the Soviet-era Mir space station and the International Space Station.
Although the Proton can be regarded as one of the most successful heavy boosters in history, the March failure was the third in three years and a successful outing for the Inmarsat satellite was deemed absolutely essential to maintain market confidence in the rocket.