Europe's Euclid space telescope is scheduled to blast off on Saturday on the first-ever mission aiming to shed light on two of the universe's greatest mysteries: dark energy and dark matter.

The launch is planned from Cape Canaveral in Florida in the late morning on a Falcon 9 rocket of the US company SpaceX.

The European Space Agency was forced to turn to the rival firm of billionaire Elon Musk to launch the mission after Russia pulled its Soyuz rockets in response to sanctions over the war in Ukraine.

After a month-long journey through space, Euclid will join its fellow space telescope James Webb at a stable hovering spot around 1.5 million kilometres from Earth called the second Lagrangian Point.

From there, Euclid will chart the largest-ever map of the universe, encompassing up to two billion galaxies across more than a third of the sky.

By capturing light that has taken 10 billion years to reach Earth, the map will also offer a new view of the 13.8-billion-year-old universe's history.

Scientists hope to use this information to address what the Euclid project manager Giuseppe Racca calls a "cosmic embarrassment": that 95 percent of the universe remains unknown to humanity.

Around 70 percent is thought to be dark energy, the name given to the unknown force that is causing the universe to expand at an accelerated rate. And 25 percent is dark matter, thought to bind the universe together and make up around 80 percent of its mass.

Euclid consortium member Guadalupe Canas told a press conference that the two-tonne space telescope was a "dark detective" which can reveal more about both elements.

Euclid, which is 4.7 metres tall and 3.5 metres wide, will use two scientific instruments to map the sky. Its visible light camera will let it measure the shape of galaxies, while its near infrared spectrometer and photometer will allow it to measure how far away they are. (AFP)