London-based communications company Inmarsat successfully launched its latest satellite earlier today, putting the group on course to completing its global mobile broadband network.

Following ten years of development and $1.5 billion in investment, the six-tonne Inmarsat-4 satellite - which is the size of a double decker bus and boasts a solar panel wing span of 90 metres from tip to tip - was dispatched into orbit on the back of a Proton Breeze M rocket from the Baikonur Cosmodrome in Kazakhstan.

The satellite is the third and final in the group’s I-4 constellation. The first two satellites, both launched in 2005, already cover 85 per cent of the world’s land mass and 98 per cent of the world’s population. Once the new satellite moves into place over the next few weeks it will fill in the final hole in the group’s network, providing satellite broadband coverage across Eastern Australia, Japan, New Zealand and the Pacific ocean.

Lift-off occurred at 11.43pm last night – 4.43am in Kazakhstan - but the satellite was not fully separated from the Russian-made rocket until almost nine hours later, at 8.46am this morning.

Shares in London-listed Inmarsat rose as much as 15p on the news, finally closing up 10.25p, or 2.10 per cent, at 498.25p.

Today’s launch will come as a relief for the makers of the Proton rocket at the Khrunichev plant in Moscow, as well as for Inmarsat.

Earlier this month Inmarsat was forced to delay its original August 4 launch date when a fault was discovered during testing of the rocket stage.

The rigorous tests followed the Proton’s disastrous previous launch, in March, when the rocket detached an American communications satellite before it had reached the planned orbit, rendering it useless. It was the third failure in as many years for the Russian company.

Inmarsat’s new satellite is 60 times as powerful as the whole fleet of its predecessors, the Inmarsat-3 range, and provides broadband speeds of 500Kb - almost 8 times faster than current capacity.

Andrew Sukawaty, chief executive and chairman of Inmarsat, said: "While other mobile satellite companies are talking about finding their next generation of satellites, we have just completed ours.

“Once the third I-4 is operational, Inmarsat will have the only fully-funded next-generation network for mobile satellite services.”

With the satellite now successfully detached, the company said 80 per cent of the risk is considered over. The satellite will now undergo several weeks of tests and manoeuvres before being positioned above the Pacific ocean.

Inmarsat’s satellites are controlled from their head office on the Old Street roundabout in London.

The group’s mobile broadband service is used by shipping, oil exploration, defence and aviation industries as well as aid agencies.

Inmarsat also hopes its network will be used by airlines, including RyanAir, when they roll out inflight mobile services, which are expected to take off within the next two years.

At the end of last month, Harbinger Capital, the US hedge fund investor, announced it intends to make an offer for Inmarsat and hopes to combine the company with SkyTerra Communications, the US satellite company, in which it has a 48 per cent stake.

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