A British-built spacecraft is set to begin an epic five billion mile journey to planet Mercury tomorrow.
BepiColombo is due to be launched from the European space port at Kourou, French Guiana, at 0245 UK time on Saturday October 20.
The European Space Agency (ESA) spacecraft will take seven years to reach the planet closest to the sun.
In 2025 it will place two probes, one European and the other Japanese, in orbit around Mercury, the least explored world in the solar system.
The Mercury Transfer Module (MTM), carrying the orbiters, was built in Stevenage by the Defence and Space division of aerospace company Airbus.
Key elements of ESAs Mercury Planet Orbiter we’re also assembled by Airbus in the UK.
Scientists hope the £1.4 billion mission will unravel some of Mercury’s mysteries, such as the reason for its oversized iron core, its spectacular volcanic vents, and tantalising hints of water ice in shadowy parts of the scorching hot planet.
The answers they get will shed new light on the origins and evolution of the solar system.
A key feature of BepiColombo is that it is the first interplanetary mission to employ advanced electric ion propulsion technology.
Four Star Trek-style “impulse engines”, two firing at a time, will emit beams of electrically charged, or “ionised”, xenon gas.
They will be used not to accelerate the craft but to act as a brake against the sun’s enormous gravity.
A complex series of fly-bys past the Earth, Venus, and Mercury will also help to reduce BepiColombo’s velocity by 7km per second.
At top speed after launch, the spacecraft will be moving at 60km (37 miles) per second.
An Ariane 5, ESA’s most powerful rocket, will blast BepiColombo onto an “escape trajectory” that will free it from the shackles of Earth’s gravity immediately.
One of the biggest challenges for mission planners was ensuring the spacecraft could withstand searing temperatures of more than 350C so close to the sun.
Protective measures include a heat shield, novel ceramic and titanium insulation, ammonia-filled “heat pipes”, and in the case of the Japanese orbiter, “roast-on-a-spit” spinning.
A suite of 11 instruments on the MPO will map the surface of Mercury and probe its chemical composition for up to two years.
Meanwhile, the Japanese space agency Jaxa’s Mercury Magnetospheric Orbiter will focus on the planet’s unusual magnetic field.
Justin Byrne, head of science at Airbus, said: “Mercury is extremely hot and it’s an extremely difficult place to get to because of the gravity of the sun.”
One of BepiColombo’s main instruments, the Mercury Imaging X-ray Spectrometer (Mixs), was designed and built at the University of Leicester.
The ion thrusters were supplied by the UK defence technology company QinetiQ.
Only two spacecraft have previously visited Mercury. Nasa’s Mariner 10 flew past the planet three times in 1974-75 and the American space agency’s Messenger probe orbited Mercury from 2011 to 2015.
BepiColombo was named after the late Giuseppe “Bepi” Colombo, an Italian scientist and engineer who played a leading role in the 1974 Mariner 10 mission.
Speaking before the launch, ESA director general Professor Jan Woerner, said: “For me, science is the basis of humankind because it teaches curiosity.
“It is fulfilling this quest for information, and at the end of the day we don’t know what we will find. This is really an impressive scientific mission.
“We are doing science, we are doing technology, we are doing international co-operation, and we are doing something for society.”
Asked if ESA was competing with Nasa, he said: “There is no competition, at least for me.
“Competition is a driver for sure, but co-operation is an enabler. I think the race in space is over.”
Professor Emma Bunce, from the University of Leicester, who is in charge of the Mixs instrument, said: “Being here makes it much more real. It’s an amazing experience.
“I’d be lying if I said I wasn’t slightly nervous but I’m confident the launch will all go well.
“I’m really, really excited that we’re going to get our instrument on its way to Mercury.”
Prof Bunce added: “It’s the two spacecraft aspect of the mission that’s the real key.
“We have a spacecraft that’s dedicated to studying the planet itself and its exosphere and interior, and a Japanese spacecraft dedicated to looking at the wider environment of the planet and how the sun drives the magnetosphere in a dynamic way.”