The Thaicom 4 (Ipstar) craft, operated by Thailand's Shin Satellite, will provide net access across Asia-Pacific.

The 6.5-tonne satellite beats the previous heaviest telecoms satellite which was the Anik F2 satellite.

Thaicom 4 (Ipstar) was launched into orbit by an Ariane 5-Generic rocket, operated by Arianespace.

The launch from the European Space Agency's (ESA) Kourou spaceport in South America on Thursday (0520 local time in Kourou, 0820 GMT) marks the 18th successful mission for the standard Ariane 5-Generic launcher.

It had originally been scheduled for 12 July, but was postponed for technical reasons by Arianespace.

The $400m satellite, which was lifted into GTO (Geostationary Transfer Orbit), should have a life expectancy of 12 years.

The European company, Arianespace, currently dominates the satellite launch business globally with its Ariane 5-Generic rockets, which can deliver about six tonnes to orbit.

Commercial telecommunications satellites tend to orbit Earth at distances of about 36,000km. Satellites in GTOs are in-between LEO (Low Earth Orbit) and GEOs (Geostationary Orbit).

They travel an elliptical orbit along the Equatorial plane until they get to GEO. Satellites in a GEO follow Equatorial orbits to match Earth's rotation so they have "fixed" locations in order to send steady signals.

Arianespace's family of launchers also includes the Ariane 5-ECA craft, a beefed-up version of the Ariane 5-Generic, capable of lifting much heavier loads into space.

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This is because the rocket can deliver several satellites at once, taking a maximum of 10 tonnes into orbit.

The ECA, considered to be the "workhorse" for Europe's launchers industry, last launched in February, carrying an eight-tonne payload into space.

That was its first flight since its disastrous maiden outing in 2002, when the rocket was destroyed as it veered out of control over the ocean.

Growing demand

The commercial satellite industry has been slowly recovering from a slump in businesses.

An industry report by the International Space Business Council released this week said that government and commercial sales should reach $158bn by 2010, up from $103bn in 2004.

The report said that government funding for space is on the rise, and that commercial orders for satellites and launches have rebounded.

It reported that new exploration initiatives were being pursued and that there was general "excitement" surrounding new businesses around radio, broadband and space tourism.

Part of the recovery has been down to more demand for satellite radio, satellite TV, as well as GPS (Global Positioning Satellite) services and systems.

Some older satellites which are currently in space are also reaching the end of their life cycles, so will need replacing. Improving technologies have extended the life time of satellites.

More than $18bn a year is being spent globally by governments and businesses on space systems. India and China had also successfully developed their independent space systems, which also boosted demand.