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Brute force at work.

A European Ariane 5 rocket
lifts off from Kourou.

For BepiColombo, Europe's
first mission to Mercury,

the real journey has begun.

Its 7.5 year flight is a major challenge

in orbital mechanics,
and will see it reach

the smallest and innermost planet

in our solar system in 2025.

There, it's discovery
mission will really begin.

A joint program with the
Japanese space agency, JAXA,

BepiColombo is one of the most complex

scientific missions ever launched.

It carries two orbiters designed

to unravel many of Mercury's mysteries.

These include an unusual magnetic field,

strange surface features called hollows,

and ancient ice hidden in polar craters.

- One spacecraft is provided by ESA,

which is an MPO, we call it MPO,

Mercury Planetary Orbiter,
and this spacecraft

has to focus more on the planet.

We want to observe the planet
through remote sensing,

characterize the surface
around the craters,,

wanting to know about the
composition of the surface,

the interior of the planet.

And in addition, we have
a second spacecraft,

and this spacecraft is called
the Mercury Magnetospherical

Orbiter, more focused on the environment.

And this spacecraft is provided

by the Japanese space agency.

- And we know the Mercury's very hot,

and we have to make the satellite

that can survive in
that harsh environment.

And we know, well, it is very difficult,

and we started, when we started,

we already some development,

and we think that we can do it.

But actually, the hot is much harder

than we expected, and takes a long time.

But now, you see, this
is the flight model.

BepiColombo's
road, design, research,

and development phase,
construction assembly

and testing phase has bene
long and hard, culminating

in the launch from the European
space port in French Guiana.

- Mercury is three
times closer to the sun,

and therefore the radiation, or the heat,

which we are getting from
Mercury is 10 times higher.

So everything which we had
to develop had to withstand

the higher temperatures, but
also the higher radiation doses

which we got from the solar wind.

And for that, we need special insulation

of our spacecraft, special
materials to be developed,

for the antenna, for the solar panels,

and yeah, that was a very big challenge

for the mission in itself.

- Now, of course, we do the health checks

to verify the system is healthy,

and we do the alignment,
mechanical checks,

electrical checks all over.

We check the propulsion subsystems,

to see if the propulsion
elements are still leak tight

in preparation for the fueling.

Hardware apart,
training of the scientists

and technicians back
on earth was extensive,

requiring years of preparation.

- Okay, so I have no questions.

- The simulations
campaign is the first time

that all the experts involved
in the BepiColombo spacecraft,

design, integration,
testing, and operations,

worked together as a single team.

The campaign is essential for this group

to learn to work as a single team,

to train the decision making process.

The campaign ins also
very important for us

to fine-tune our plans and procedures.

It's the first time that we
exercise the flight plans

and procedures in a realistic context,

taking into account
communication constraints,

ground station and timing.

- In preparing for a mission like this,

we have to carefully
train all the aspects.

What we actually do in the rehearsal,

we do in preparation of a launch.

We train the teams to work together.

We train the teams to work
with the flight procedures,

and also we train the teams

as much as we can in flight conditions.

So normally when we test before,

we test with many work arounds.

What we try to simulate here
is actually to replicate,

as much as possible, flight condition.

And we typically do between 20 and 30

of these rehearsal before a flight.

With a nail biting
launch sequence complete,

for many it's time to sit back, and wait.

- The cruise will be about seven years.

We will fly by once the
Earth, two times Venus,

and six times Mercury itself,

before we come into the
orbit, which allows us

to capture, with the small gravity

of planet Mercury against the big sun.

That means when we fly, we
constantly brake against the sun,

because we fly into the inner side

of our solar system, yeah?

And then when you fly
towards the most heaviest

element there, you constantly accelerate.

We don't want that.

That's why we decelerate.

- Because this planet
is so close to the sun,

you need to have a lot
of energy to go there.

It's even easier to send a spacecraft

to Pluto than to Mercury.

You have to brake into
the gravity of the sun,

and you need a lot of energy.

And for that reason, our
mission takes quite a long time,

because we also need the
help of planetary flybys

in order to bring our spacecraft in.

Then, we want to send two
spacecraft in an orbit

around Mercury, and that, in itself,

is also a problem,
because on the other hand,

you need to brake against the sun,

but, on the other hand,
you also need to accelerate

your spacecraft to bring
it in the same speed

as Mercury goes around the sun,

and then to finally drop it
into an orbit of the planet.

I'm working now 14 years on this mission,

so it's really like a baby growing up,

and leaving the house finally.

So for me, it's a special moment.

- BepiColombo's main component parts

are two orbiters and one transfer module.

These took four weeks
to disassemble and pack,

and required 70 shipping containers

and four cargo planes
to ensure safe delivery

to the European space port at Kourou.

Spacecraft have got up close
and personal with Mercury

twice before, thanks to
NASA's Mariner 10 probe,

and some 40 years later,
the Messenger mission.

Messenger mapped the surface,
and identified strong evidence

for water ice in shaded craters,

but its mission also raised new questions

about this mysterious planet.

This latest probe has a
sophisticated suite of sensors

and instruments that will come into play

when it reaches orbit around Mercury.

- So, the big step forward for BepiColombo

is the fact that we have two spacecraft,

the European Space Agency spacecraft,

which is looking
directly, designed to look

at the surface of the planet,

and to study the planet in detail,

and the orbiter's designed such

that you maximize the objectives

that you can do relating to the surface.

And the second spacecraft is designed

to look at the environment, and so,

having two spacecraft will enable us

to do a great deal of new science

compared to the previous missions.

- With BepiColombo, with
the two satellite approach,

we have one satellite, the
MMO, sitting in the solar wind,

and the other one is
inside the magnetosphere,

so we can see what is coming
towards the magnetosphere,

and what is driving changes
within this magnetosphere.

- We have 11 instruments
on board the spacecraft.

And when we are at
Mercury, these instruments

are gathering data, and
then they will store it in,

effectively, a large hard drive,

which we have on board the spacecraft.

That data is then collected
over a number of hours,

and when we have a visibility
with the spacecraft

in Mercury, typically it's every 16 hours

we can talk to the spacecraft at Mercury.

The data is then down linked using

a very large high gain antenna.

It's a very powerful
antenna in order to have

a data rate of about
340 kilobits per second.

If you compare it to your home
internet, this is nothing.

It's a very slow data
rate, but it's very fast

considering we are very close to the sun,

and we might get some interference

from the energy from the sun.

So it's as powerful as we can have

with the resources we have
on board the spacecraft.

With the
assistance of gravity flybys,

the spacecraft will rely on its solar

electric propulsion system.

It consists of four TX ion thrusters,

fueled with xenon gas that is ionized

and electrically propelled out,

providing thrust for months at a time.

The thrusters will rely
on the spacecraft's

solar arrays for power.

The T6 thrusters can accelerate

BepiColombo 15 times more efficiently

than a conventional chemical thruster.

- So at Earth, the solar flux is 1.4,

more or less, 1.4
kilowatts per square meter.

As we approach Mercury, which is the most,

innermost plant of the solar system,

that solar flux has risen 10 times.

So now we have 14
kilowatts per square meter.

Now you might think that's a good thing,

in the sense that it gives you more energy

to turn into electricity, to
be able to run your thrusters,

but it turns out that that immense flux

that we're getting from the sun

also drives the temperature
of the spacecraft very high,

and in particular, our solar
arrays, which are sensitive

to high temperature, need to be protected.

Now, we do that in a
number of different ways.

We keep as much of the
open surface covered

in little mirrors that we call OSRs,

optical surface reflectors,
or with specially developed

white coatings, which help to
reject the heat from the sun.

But perhaps the biggest
mechanism that we use

to keep the solar array
cool is to off point.

Rather than pointing the solar
arrays directly to the sun,

we point them at a very shallow angle.

And what that does, is it means it keeps

the thermal energies under control,

while still giving us the necessary energy

to turn into electric
power for the thrusters.

Now, the reason why the
solar arrays are big

is because we're off pointing by so much,

that in order to get
sufficient cross section

of the solar array, the
solar array needs to be big.

Protected by
multilayered insulation,

hand stitched thermal
blankets, and a radiator

to dissipate heat, ESA's
Mercury Planetary Orbiter

will have to cope with
extreme environments.

- If a unit is getting too
hot, if one of the payloads

is getting too hot, in
order to stop that payload

from being damaged, we'll switch it off,

we'll send an emergency
message back to the Earth,

reporting that there's an issue.

We need ESA to take action, to investigate

why items are getting to hot,

and then to recover the
unit and the spacecraft.

Once they reach
Mercury in late 2025,

the orbiters will separate
from the transfer module

to begin their comprehensive
scientific mission in 2026.

- In principle, all the
planets have the same

chemical elements, because
the whole solar system

has the same chemical composition,

but it's distributed differently

in different planets, and
different environments,

so it is vital to understand
what is the ratio,

or the abundances of different
elements to understand

the structure of the surface of Mercury.

One of the advanced
censors aboard BepiColombo

is a sensitive imaging x-ray
spectrometer called MIXS,

which produces a global
map of Mercury's surface,

atomic composition, at
high spatial resolution.

- The MIXS instrument, the Mercury Imaging

X-ray Spectrometer,
looks at the fluorescence

that happens when the sun
shines on Mercury in x-rays.

So it's a bit like when you
wear a shirt in party lights,

which has been washed in the
right sort of washing powder.

The party lights shine on your
shirt, and your shirt glows,

and it's exactly the same
with the sun and Mercury.

The sun shines on the surface in x-rays,

and the surface of
Mercury glows in x-rays,

and if you detect those x-rays,

you can tell what Mercury's made of.

And what it tells you, you're actually

counting the atoms on the surface.

So it tells you, and a
very quantitative way,

exactly what the surface
layer of Mercury is made of.

- So I would say, one of
the most exciting things

about MIXS, is the fact
that we will be able

to produce the first
images in x-ray wavelengths

of Mercury's surface, and
that is going to be able

to give us a great deal
of new information,

both on a global scale
and on a local scale,

of how the composition of Mercury varies

over its entirety of it's surface.

Another aspect of the MIXS
science, which I'm personally

very excited about, is the
fact that we can also see

x-rays from the surface,
which are being produced

by particles from Mercury's magnetosphere,

actually precipitating on to the surface,

and producing x-rays that we
will be able to also measure.

So we can have an extra aspect
to the science that we can do

relating to how Mercury's magnetosphere

interacts with the surface.

Among the mysteries
revealed by Messenger

are irregularly shaped depressions,

known as hollows, found in clusters

over a wide range of
latitudes and longitudes.

These hollows have bright interiors,

and halos with a fresh appearance

that suggests they are
geologically very young.

- I think that there are two mystery,

or two very intriguing
objectives of BepiColombo.

The first one, are the hollows.

The hollows are features
discovered by Messenger.

These features seems
to be quite distributed

all over the south face of Mercury,

and is something related to the volatile,

that come to the south face,

after an impact, after a volcanic event.

But, of course, we need BepiColombo

to really characterize it, to understand,

which is the origin of the hollows.

There are also clear traces

of much more recent hollows

where the surface has been eaten away

by some process that removed
solid, volatile substances,

such as sulfur, chlorine,
sodium, and potassium as vapor.

- And this is because we don't
have the composition data.

We have seen, we can
measure the dimension,

the size of the hollows.

We can have an idea of the
distribution, but no more.

And also, of course,
Messenger didn't get so many

high resolution images, and didn't have

the digital terrain mode, the 3D images

at high resolution, as we
will provide on SIMBIO-SYS

In other words, I think that the hollows,

the hollows are one of
the most interesting

discovery made by Messenger.

Existing evidence indicates

that if combined and
spread out over a city

the size of, say, Washington,
the amount of water ice

concealed in Mercury's polar craters

would be over two miles thick.

- The second point is the water,

because even Messenger said that yes,

on the polar region we
may have some water ice,

hidden just in the shadow of the craters,

because at the polar
region, there are some floor

of the craters, some wall of the craters,

that are not, that are always in shadow,

as occurred on the moon.

But the Messenger didn't
have the instruments

to observe if it is, to make
a direct measuring of water,

as occurred on the moon.

And BepiColombo and
SIMBIO-SYS will be able

to do it with our spectrograph.

If confirmed by BepiColombo,

the story of how the inner
planets, including Earth,

acquired water, and some of
the chemical building blocks

for life becomes much clearer.

It would support the theory
that organic compounds,

as well as water, were
delivered from the outer

solar system to the inner planets,

and may have led to
prebiotic chemical synthesis,

and as a consequence, life on Earth.

- So studying Mercury is
crucial to better understand

the formation of our solar
system, how Earth is formed

and evolved, and where we are coming from.

So Mercury is, in a way, a missing piece

in the big puzzle of the
formation of the solar system,

and a crucial end member,

because it's close to the sun, and if you

want to get the full
picture, you have to look

at the planet close to
the sun, as we also did

in past missions that we were looking

at the comets or planets further out.

- We all have our individual
science objectives

for each of our instruments,

and what we're starting to do now

is to bring all of our ideas together,

which obviously, are
complementary to each other,

and we can start to form
a broader set of goals

at working group level, so
the surface working group

and the environment working group,

and that helps us to,
again, maximize the science

that we can get from the mission

by coordinating what it
its that we want to do,

potentially looking at specific targets

on the surface, and that kind of thing.

We can work together to get the best

from the mission that we possibly can.

ESA science
and engineering teams

have already been working on BepiColombo

for more than a decade,
but with a long journey

ahead, the recent launch
marks only the beginning

of the next intriguing stage

of BepiColombo's voyage of discovery.