Spacecraft heads out on a mission to Mercury
A British-built spacecraft is set to blast off from the Earth bound for Mercury, the mysterious planet closest to the Sun.
Bepicolombo, one of the most ambitious missions ever undertaken by the European Space Agency (Esa), will send two orbiters to explore the world where surface temperatures reach 450C.
One probe was built by satellite makers Airbus Space and Defence at its assembly centre in Stevenage, Hertfordshire. The other was constructed in Japan.
The mission, due to launch on 20 October, has cost an estimated €1.6 billion (£1.4bn).
Unlike any other interplanetary spacecraft in history, Bepicolombo carries a futuristic ion electric propulsion drive, also designed and built in the UK.
Four ion engines on the Mercury Transfer Module (MTM) transporting the orbiters will provide thrust by electrically ejecting a “plasma” of charged xenon gas.
Although the force an ion motor produces is very small – far less than that of a chemical rocket – it can be kept firing for a long period of time.
The four-tonne spacecraft will be launched into an “escape trajectory” orbit by Esa’s most powerful rocket, the Ariane 5, from the European spaceport at Kourou, French Guiana.
It will then set off on a sevenyear 8.5 billion kilometre (5.2 billion mile) journey involving a complex series of gravityassist fly-bys around the Earth, Venus, and Mercury.
As it circles towards the Sun, Bepicolombo will use its ion drive and the fly-bys not to build up speed but to brake and overcome the star’s powerful gravity.
After playing tag with Mercury six times while crossing the planet’s orbital path, the spacecraft will arrive at its destination in 2025.
Esa’smercuryplanetorbiter (MPO) and the Japanese space agency Jaxa’s Mercury Magnetospheric Orbiter (MMO) will then separate to study the little-known sun-baked world for up to two years.
MPO will make global maps of Mercury’s surface chemistry and geological features, while MMO investigates the planet’s internal structure and magnetic field.
One of MPO’S key instruments, the Mercury Imaging X-ray Spectrometer (Mixs), was designed and built at the University of Leicester.
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, taking photos of the surface.
Dr Jerry Bolter, project manager at Airbus Defence and Space, said: “The only other spacecrafttogoinorbitaround Mercury was Nasa’s Messenger. That was a very, very light spacecraft and nowhere near as capable as Bepi will be. The scientists describe Messenger as the hors d’oeuvre and Bepi as the main course.”
A key challenge for mission scientists was coping with temperatures of more than 350C. In Greek mythology, Icarus flew too close to the Sun and paid the ultimate price. Likewise, Bepicolumbo’s orbiters would face destruction without adequate protection. Among the measures employed were a heat shield, multi-layers of novel ceramic and titanium insulation, and ammonia-filled “heat pipes” that conduct heat to a radiator face always pointed away from the Sun.