BepiColombo mission blasts off on seven-year journey to Mercury – Science News


An ambitious new mission has launched off to Mercury, our inner-most planet.

Key points

  • Bound for Mercury, BepiColombo is actually two spacecraft stuck together
  • It will circle the inner solar system using the gravity of Earth and Venus to slingshot itself towards Mercury
  • The mission will be tracked by ground stations around the world, including in Australia.

The BepiColombo mission, which lifted off from French Guiana, is a joint project between the European and Japanese space agencies.

If it is successful, it will be only the third space mission to get up close and personal with this mysterious world.

“It’s a hard place to get to, and it’s a really harsh environment,” said Glen Nagle from the Canberra Deep Space Communication Complex, which will play a role tracking the mission.

So hard that it will take seven years to get there, and a lot of circle work in the inner solar system to catch up with its target, before going into orbit around Mercury in December, 2025.

“It’s certainly the most ambitious [mission] the Europeans have flown,” he said.

What are we trying to find out?

The BepiColombo mission will take up where NASA’s Messenger mission left off.

The Messenger spacecraft was the first spacecraft to orbit around Mercury.

Between 2011 and 2015 it mapped the planet’s surface, discovered hints of water and other organic compounds and measured its magnetic field.

“It could really only get decent high resolution views of the northern hemisphere of Mercury.

“The BepiColombo mission can take a better look, a much higher resolution view of the surface of the planet, and tell us a little bit more about its interaction with the sun.”

It could also tell us more about the planet’s interior and its weird magnetic field.

“One of the mysteries that Messenger came up with is that this planet has a large iron core,” Mr Nagle said.

“On Earth [the same size core] would generate our magnetic field from the centre of the planet, but for some reason it seems that Mercury’s magnetic field has shifted by about 20 per cent from the core of the planet.”

And then there are the tantalising hints of water ice at the planet’s polar caps.

“BepiColombo will be in a polar orbit, so it will look directly down into those deep shadowed craters where we think water ice could exist,” Mr Nagle said.

The mission

The mission is named after Italian mathematician and engineer Giuseppe Colombo, who was the first to calculate the maths behind Mercury’s rotation and orbit.

He also helped NASA work out how to use the gravity of Venus to help get the Mariner 10 spacecraft to Mercury in the 1970s.

“It’s a nice thing to see that mathematics and engineering honoured by naming the mission after him,” Mr Nagle said.

BepiColombo is actually two spacecraft stuck together along with a propulsion system and a heat shield to protect its sensitive instruments from melting as it endures temperatures of up to 400 degrees Celsius.

The whole stack, which is about 6 metres high and has two 14-metre solar wings attached to the propulsion system, will travel as one for the seven-year journey.

Once it reaches its destination in December 2025 these components will separate into two individual spacecraft.

The European spacecraft, known as the Mercury Planetary Orbiter, is about the size of a bus with a solar panel. It will use an array of instruments such as cameras, spectrometers and altimeters to get a detailed picture of the planet’s surface, atmosphere and magnetic field.

The Japanese component of the mission, known as the Mercury Magnetospheric Orbiter, is an octagonal-shaped craft about the size of small dinner table. It will also study the planet’s magnetic field and how it interacts with the solar wind and interplanetary dust.

“Because you have two separate spacecraft they can complement each other’s observations,” Mr Nagle said.

“If one observes something interesting, the other one from its different perspective could also observe it using a different suite of instruments so you can get more information.”

How it will get there

The BepiColombo mission will fly by Earth and Venus and use their gravity as a slingshot.

It will fly by Earth in 2020, then fly by Venus in 2020 and 2021, then fly by Mercury six times.

“The primary task will be to get enough speed to keep up and catch up with Mercury in its orbit around the sun.

“Mercury orbits around the sun every 88 days. It’s quite a fast orbit, so [the mission] needs these gravity slingshot effects to get it from one place to another.”

Thanks to these manoeuvres it should be in the perfect position to go into orbit in December 2025.

When it does, the space craft will separate.

It will drop its propulsion system, the Japanese spacecraft will part from the European spacecraft, then the European spacecraft will ditch the sunshield.

The crafts’ orbit will continue to tighten for another three months. The science program will start in March 2026 and continue for at least two years.

“A lot of that comes down to fuel to keep the spacecraft pointed where it needs to be pointing,” Mr Nagle said.

“A lot of missions tend to be very conservative on their estimates for how long they will go for and they quite often go for a lot longer.”

The science mission of Messenger for example, was extended another two years before it was sent hurtling to its fiery death.

Tracking its progress

Throughout it’s journey, BepiColombo will be tracked by a number of ground stations around the world.

The European Space Agency (ESA) has tracking stations in Australia, Africa and South America.

“The ESA has a small station with a 35-metre antenna out near New Norcia not far from Perth,” Mr Nagle said.

“They will be the main tracking station during the early phases of its cruise towards the planet and some of these initial fly-bys.”

But, he said the Canberra Deep Space Communications Centre, which is part of NASA’s Deep Space Network (DSN), will shadow the mission and provide back-up support in critical phases such as the fly-bys.

“That’s when you would tend to use the larger capacity of the DSN to support the mission itself,” Mr Nagle said.

“When the mission goes into its science phase [in March 2026] the DSN will play an ongoing role sending commands up to the spacecraft and getting data back and relaying it around the world to scientists.”

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