By Pallab Ghosh BBC science correspondent at Kourou, French Guiana

Will the ion drive work?

Then, as the solid rocket boosters fired, for a moment I saw the tropical night turn to day, filling the sky with an eerie glow, making the spaceport itself seem as if it was on another world.

As the rocket sailed up to the heavens, there was the most crucial part of the launch.

That was the separation of the solid rocket boosters. Two minutes into the launch they peeled off, descending like fallen angels into the depths of the Atlantic Ocean.

A relief for the launch crew, but as I headed back to mission control I saw the night's work had only just begun.

For them, another critical moment came half-an-hour into the launch.

The job was now to deploy Smart 1 and the two telecommunications satellites in the payload.

A delicate cosmic ballet, as one by one they left the comfort of their mothership to begin a solitary life in space.

Then 42 minutes into the launch sequence, the last spacecraft, Smart 1, emerged and readied itself for its epic voyage to the Moon.

Moment of truth

Only then did the crew at mission control allow themselves a round of applause and a small celebration.

The jungle turned from night to day as the rocket blasted off

Control was handed over to engineers in Darmstadt in Germany. Their job - to ensure that Smart 1 unfurls its solar wings and begins charging its batteries.

And on Tuesday, the real moment of truth as the experimental ion engines are switched on.

There is joy tonight at the Kourou spaceport, but as the euphoria fades the real work begins and the answers to the scientific and technological questions will gradually become clear.

Will the ion drive work? Will it survive the intense radiation of the Van Allen belts on its 18-month journey?

When it arrives, will its miniaturised instruments be able to perform the task for which they were built?

If all goes well, the technologies will form the basis of a new generation of cheaper space probes.

Smart 1 could be the first of a new fleet of spacecraft, enabling exploration to become more commonplace and heralding a new era of discovery.