If you're just joining us, welcome along as we count down to the launch of one of the European Space Agency's most ambitious ever missions - above is the scene on the launchpad in French Guiana.

In less than 30 minutes - at 13:15 BST - an Ariane 5 rocket is expected to send a spacecraft towards Jupiter and its icy moons.

You can watch BBC coverage of the build-up to the launch, and the moment itself, by clicking play at the top of the page or on BBC iPlayer here.

Rebecca Morelle
Science editor

Getting a rocket off the ground is always a nerve-wracking moment.

Never more so than when you have a mission that’s taken years to put together, has involved thousands of scientists and has cost more than a billion pounds.

But there’s an extra level of stress with today’s blast off - the launch window lasts for a single second.

That’s right - one second. Either it launches at 1315BST (1215GMT) - and the four billion mile journey begins. Or it stays put on the launchpad.

So why such a minuscule launch window?

Well, the spacecraft needs to get to the Jupiter system using as little fuel as possible - and this means travelling a circuitous route pinging through the inner solar system, using flybys of Earth and Venus, to get it to its destination over the course of eight years.

So all of the planets need to line up perfectly for this to happen - and that requires ultra-precise timing at the moment of launch.

But the good news is, if today’s one-second launch window doesn’t work out, they have a one-second window every day until the end of April - so there are plenty of chances to try again.

As with all high-profile launches to space a lot will depend on the weather conditions.

BBC weather presenter Tomasz Schafernaker looks at these conditions around the Kourou spaceport where Juice is set to take off from - he says there is a risk of storms in the area but hopefully these will be isolated and the weather for the launch will be fine.

How could life exist on Jupiter’s Moons?published at 12:27 British Summer Time 13 April 2023

12:27 BST 13 April 2023

Rebecca Morelle
Science editor

The giant moons of Jupiter are bleakly beautiful - but they don’t immediately seem to be a place where life could thrive.

They’re far away from the sun, covered in thick layers of ice and are blasted with high levels of radiation.

But it’s the possibilities of what lies beneath the icy crust that has grabbed scientists' attention.

Scientists think there are vast salty oceans that could descend more than 100km down. And even though there’s no direct sunlight down there, the Moons are thought to be warm at their core, providing a vital source of heat.

If these oceans are mixing with a mineral-rich sea floor, it could provide the right conditions for life to exist.

We know this happens in our own oceans on Earth - life happily exists at even the deepest depths in the most hostile waters.

The question scientists want to answer is whether this is possible on Jupiter’s moons too?

Dr Caroline Harper, head of space science at the UK Space Agency, spoke to the BBC a little earlier.

She says there’s good evidence to suggest that underneath the ice on Jupiter’s large moons there’s a “giant saltwater ocean, more water on Ganymede certainly than even on the whole of Earth”.

“Where there’s water, there’s the potential for life,” Dr Harper adds, “and now we need to go and have a dedicated close survey to confirm whether that salt water ocean exists and to assess whether the conditions for life could exist under the ice”.

Asked about her confidence in the mission reaching its final destination, Dr Harper says “it’s a really ambitious mission”.

Radiation from Jupiter and the distance from the Sun are two complicating factors, she explains it is "the most powerful science instrument payload, I think, we’ve sent to the outer solar system and all of the instruments on board have to cope with a really harsh radiation environment when they arrive at Jupiter, and they have to cope with being a long way from the Sun”.

She says the team has done everything they can and they’ll be glad when in eight years time they start downloading data.

One of Europe's most ambitious space missionspublished at 12:08 British Summer Time 13 April 2023

12:08 BST 13 April 2023

Jonathan Amos
Science correspondent

The Jupiter Icy Moons Explorer, or "Juice" as the European Space Agency has named it, has been in the planning for more than a decade.

Even with a successful launch on an Ariane rocket in the coming hours, the spacecraft won’t arrive in the vicinity of the Solar System’s largest planet until 2031.

It’s a long way, and the satellite must use a gravitational sling-shot technique around Earth and Venus to give it the necessary energy to make the journey.

But, when it does get there, Juice will examine three of Jupiter’s moons - Ganymede, Callisto and Europa - to see if their sub-surface oceans of water might be habitable.

To be clear, Juice won’t be detecting alien fish on these moons, but it could say whether their hidden water has a chance of supporting simple microbial life.

Malu Cursino
Live reporter

Image source, ESA

Hello and welcome to our live coverage.

The European Space Agency's Jupiter Icy Moons Explorer mission - known as Juice for short - is scheduled to take off from French Guiana, in South America, in a little over an hour (13:15 BST, 09:15 local time).

From our newsroom in London, we'll be following the Ariane-5 rocket lift off from the spaceport in Kourou. If all goes well, it should reach the gas giant in eight years.

That's when the exciting research into Jupiter's three largest moons - Ganymede, Callisto and Europa - will begin, as scientists work to understand whether simple life can be supported underneath the surface of Jupiter's icy moons.

The pressure is on as the mission has a one second window to launch in - more about that to follow.

With me are Heather Sharp and Thomas Mackintosh, with Science correspondent Jonathan Amos and Science editor Rebecca Morelle also on hand - we'll be bringing you the latest updates through the final stages of the countdown and - all going as planned - the launch of the mission.

Stay with us.