It's the new space mission that will show us the Sun as we've never been able to see it before.
The spacecraft – called Solar Orbiter – is a European Space Agency-led mission – and was assembled at Airbus in Stevenage, England.
Many scientists are calling it the UK's most important mission for a generation.
BBC science reporter Laura Foster explains what SolO will be doing and how it will help us improve technology here on Earth.
The spacecraft is due to be launched from Cape Canaveral in Florida at 23:03 local time on Sunday 9 February (04:03 GMT on Monday 10 February).