The third flight of the Ariane 5 rocket is far more important that it appears.

The first flight of the Ariane 5 rocket in June 1996 ended in disaster when it exploded after just 37 seconds.

The cause was traced to a software problem; the wrong program had been used to control the rocket's ascent.

Waiting for launch

In retrospect many scientists said it was a stupid way to lose a rocket and payload that cost hundreds of millions of pounds.

The software was eventually fixed for the second flight, which went smoothly.

But the third flight - the last test launch - will demonstrate if Ariane's problems are really behind it.

This is because the company that sells Ariane 5 flights, Arianespace, have ordered 13 more rockets that it hopes to offer to paying customers.

They have a good track record. The previous Ariane versions, Ariane's 1 to 4, have since 1979 captured two-thirds of the world market for satellite launches.

Simpler than before

But by 1987 it became clear that the current Ariane rockets were not powerful enough to effectively launch the larger satellites that would be built in the future, so Ariane 5 was born.

Ariane 5 is meant to be more powerful and simpler than previous Arianes. It can put a satellite weighing nearly 7 tonnes into orbit compared with 4.4 tones for Ariane 4.

Analysts believe communication satellites will be larger in the future and that more of them will be launched into low orbits.

Already, before Ariane 5 has entered the commercial market, there are upgrade plans so it can carry even heavier satellites.

If it proves it can take off without incident and if the trend to larger satellites continues, then Ariane 5 should have a good future. In a few years it could be the dominant force in the marketplace.