We did not reach the desired orbit - we apologise to our clients

Jean-Marie Luton, Arianespace

The rocket was carrying the experimental Artemis communications satellite and a Japanese satellite for direct broadcast television.

Esa officials said they believed the Artemis satellite could use its engines to boost itself up to its planned orbit, although as this would use precious fuel its expected lifespan of 10 years was likely to be shortened.

However the Japanese satellite, would not be recoverable, they said.

Loss in thrust

The Artemis satellite has two engines, while the Japanese Bsat-2B television orbiter has only one.

Arianespace, Esa's commercial launch arm, said the suspected cause was a failure in the rocket's upper-stage engine.

The satellite was meant to orbit 36,000 km above the Earth

"According to an initial evaluation, the flight proceeded normally during the firing of the first stage, then a malfunction was detected on the upper-stage engine, which suffered a 20% loss in thrust," Arianespace President, Jean-Marie Luton, said.

"The navigational system made corrections to compensate, but was unable to overcome the loss of velocity, which was 50 metres (162 feet) per second less than scheduled," he added.

Mr Luton apologised to Arianespace's clients for the failure to reach proper orbit.

Good record

The $850m Artemis satellite was partially insured. Bsat-2B officials were not available to comment.

Artemis is a demonstrator for future space technologies

The Ariane programme, which began in 1979, has a good record. Only eight of its 141 missions have ended in failure - the most spectacular being the Ariane 5's maiden test-flight in 1996. The vehicle was destroyed 37 seconds after launch as it veered off course.

The latest failure is considered unlikely to affect Ariane's full order book.

Artemis is the most advanced telecommunications satellite yet developed by Esa and its partners. It will act as a demonstrator for new technologies.

The multi-purpose satellite is designed to conduct trials of Europe's proposed satellite navigation system, which Esa claims will be more accurate and more reliable than the American Global Positioning System.

Advanced communications

It is also meant to demonstrate new mobile communication technologies that should eventually make telephone conversations possible via satellite anywhere in Europe, North Africa or the Near East - even at sea.

Its system of propulsion, which uses ionised xenon as the propellant, should make future satellites more compact.

It is also intended to test direct satellite-to-satellite communications, including a revolutionary laser link that is so accurate the light pulses can hit a target the size of a coin at 10km (six miles).

The link is expected to replace conventional earthbound relay systems, and should dramatically improve the time it takes for satellites to pass data between each other and their terrestrial base stations.

Earth observation satellites should send down their pictures of the planet much faster, for example.