Bepi Colombo, the mission that will reveal the secrets of Mercury!
Statistically, Mercury is the planet that spends the most time close to Earth, but despite
that, only two spacecraft have visited this planet, the last being NASA's Messenger space
probe in 2011. More than a decade later, a new mission called Bepi Colombo is on its
way to revisit this planet. Why did we stop visiting Mercury for so long, and what discoveries
will we achieve with this new mission? Let's find out!
Mercury is the closest planet to the sun; at its closest point to the Earth, this is
a distance of approximately 77 million kilometers, so in a matter of distances, it is the second
closest planet to the Earth. In addition, Mercury orbits the sun every
87.9 days, so statistically, it spends more time close to the Earth than any other planet;
this is because, in a simulation conducted by the American Institute of Physics, the
orbits of rocky planets during an Earth year reveal that Mercury has the smallest average
distance from Earth and it is the planet that on average spends the most time close to the
earth.
Although, in theory, Mercury is the closest planet to Earth, we will soon see that put
into practice, this may not be very useful. Bepi Colombo
Bepi Colombo is an international mission of the European Space Agency (ESA) and the Japan
Aerospace Exploration Agency (JAXA); the mission is composed of two spacecraft, the Mercury
Planetary Orbiter (MPO) and the Mercury Magnetospheric Orbiter (MMO), which travel together to Mercury
in cruise mode to orbit and study the planet from unique points of view.
The Bepi Colombo mission lifted off an Ariane 5 rocket on October 20, 2018, and is expected
to reach Mercury on December 5, 2025. Why will it take so long?
If Mercury is the planet that, on average, is closest to the earth, why will the Bepi
Colombo spacecraft take more than seven years to arrive? Even with our modern spacecraft,
we can reach much farther planets like Mars and Jupiter in less time.
This is due to the speed; in a previous video, we explained why Mercury is the most difficult
planet to visit. In short, being so close to the sun, Mercury
has a very high orbital velocity, so our spacecraft must accelerate for a long time to be captured
by their gravity. There are two ways to reach such high speeds,
the simplest is using rockets, but this is the most expensive option since rockets are
not cheap and consume a lot of fuel. The Bepi Colombo mission is classified as
a low budget, these missions are characterized by minimizing fuel consumption, and therefore,
the option of using rockets to propel the ships in space is ruled out; the only option
left is to use gravitational assistance. Gravitational assistance to reach Mercury
Gravitational assistance is the maneuver intended to use the energy of the gravitational field
of a planet or satellite to obtain an acceleration or braking of a spacecraft or space exploration
probe, changing its trajectory. In the case of missions to Mercury, gravitational
assistance has always been used to propel the ships to reach the speed of the target
planet; the only drawback with this method of accelerating ships is time.
To take advantage of the gravitational assistance of one or more celestial bodies, the spacecraft
must orbit the object several times, pass very close to it and then continue its journey.
This process takes a long time, most of the time years, and that is why Bepi Colombo will
take more than seven years to reach Mercury, even though it is the planet that spends the
most time close to the earth. How will Bepi Colombo use gravitational assistance?
Pay close attention, as this is the most complicated part. To reach Mercury, saving the maximum
amount of fuel, a trajectory has been proposed in which Bepi Colombo will make ten orbits
around the sun before being captured by the gravity of Mercury in a route with ten flybys
that will last more than seven years. I suggest using this animation or a very similar
one: April 10, 2020, was the first close flyby
to the Earth; the second was October 15, 2020, in which it flew over Venus; the third was
on August 10, 2021, flying over Venus for the second time; the fourth occurred on October
1, 2021, in which it flew over Mercury for the first time, then the fifth flyby was on
June 23, 2022, flying over mercury for the second time, and from here it will take another
four flybys of Mercury until its gravity finally captures it.
As you can see, even though Mercury is a nearby planet, sending spacecraft to it is extremely
difficult. It takes many years of planning and execution. Nowadays, sending a spacecraft
to Mercury and Venus takes much longer than sending a spacecraft to Mars.
Mission characteristics Bepi Colombo is a joint mission carrying two
different orbiters, ESA built the main spacecraft, the Mercury Planetary Orbiter (MPO), and JAXA
supplied the Mercury Magnetospheric Orbiter (MIO).
MPO will study the surface and internal composition of the planet. This consists of a sonar stabilized
in three axes, with a mass of 1140 kilograms (without fuel), of which 80 kilograms correspond
to scientific instruments. The power consumed by the ship will be 450
watts. It will carry out its transmissions through an adjustable antenna of one meter
in diameter. It is expected to transmit a data volume of 1550 Gigabits (Gb) per year,
corresponding to an average data rate of 50 Kb/s. Its primary means of propulsion will
be ion propulsion. The MIO will study the magnetosphere of Mercury;
this is a smaller ship than the MPO and will be coupled to the latter until the moment
of reaching Mercury; once they reach their destination, they will separate from orbiting
the planet each on their own. The MIO is a probe stabilized by rotation
(at 15 revolutions per minute), with the axis of rotation oriented 90º concerning the Sun.
Its mass is 634 lb (288 kilograms), of which 100 lbs (45 kilograms) correspond to scientific
instruments. The spacecraft will consume 300 watts of power and transmit signals through
a 0.8-meter phase-coupled high-gain antenna. Like the MPO, it will also use ion propulsion.
Initially, it was planned that the Bepi Colombo mission would integrate a landing probe, which
would be Mercury's surface element (MSE). Still, unfortunately, it was canceled in 2003
due to budgetary constraints. At the time of cancellation, MSE was intended
to be a small 97 lb (44 kg) lander designed to operate for about a week on Mercury's surface.
The lander would be disc-shaped, 2 feet 11 inches (0.9 m) in diameter, and designed to
land at a latitude of 85° near the terminator region. Braking maneuvers would bring the
lander to zero speed at an altitude of 390 feet (120 m). At that point, the propulsion
unit would be ejected, the airbags inflated, and the module would fall to the surface with
a maximum impact velocity of 98 ft/s (30 m/s). The science data would be stored on board
and transmitted via a cross-dipole UHF antenna to the MPO or MIO to transmit it to Earth
finally. The MSE would have carried a 15 lb (7 kg)
payload consisting of an imaging system (a decent camera and a surface camera), a physical
properties and heat flow package, an alpha particle X-ray spectrometer, a magnetometer,
a seismometer, a ground-penetrating device (mole), and a micro rover that would explore
small regions of the planet closest to the Sun.
Sadly, we won't see any of it. First approaches
The BepiColombo mission captured its first view of its target planet, Mercury, as it
sped past in one of its close gravity-assisted flybys.
The closest approach took place at 23:34 UTC on October 1 at an altitude of 199 km from
the planet's surface. During the encounter, images were collected from the spacecraft's
tracking cameras and scientific data from several instruments.
The flyby was perfect from the spacecraft's point of view, and it's fantastic to finally
see our target planet in high resolution, waiting for our arrival.
The monitoring cameras provide black-and-white snapshots with a resolution of 1024 x 1024
pixels and are located in the transfer module so that they also capture the structural elements
of the spacecraft, including its antennas and magnetometer arm.
The images were acquired approximately five minutes after the close approach and up to
four hours later. Because Bepi Colombo reached the planet's night side, conditions were not
ideal for taking images directly on the closest approach. The closest image was captured from
a distance of about 1000 km. In many images, it is possible to identify
some large impact craters. Still, although the cratered surface looks quite similar to
Earth's Moon at first glance, Mercury has a different history than our natural satellite.
Once their primary science mission begins, Bepi Colombo's two science orbiters, ESA's
Mercury Planetary Orbiter and JAXA's Mercury Magnetospheric Orbiter, will study all aspects
of mysterious Mercury, from its core to surface processes, magnetic field, and exosphere,
to better understand the origin and evolution of a planet close to its parent star.
For example, it will map Mercury's surface and analyze its composition to learn more
about its formation. One theory is that it may have started as a larger body stripped
of most of its rock by a giant impact. This left it with a relatively large iron core,
where its magnetic field is generated, and only a thin rocky outer layer.
Mercury has no equivalent to the moon spots we observe on our natural satellite: its surface
is dark almost everywhere and was formed by large lava flows billions of years ago. These
lava flows show the scars of craters formed by asteroids and comets that hit the surface
at speeds of tens of kilometers per second. Younger lava flows have flooded the floors
of some of the oldest and largest craters, and there are also more than a hundred sites
where volcanic explosions have broken the surface from below.
BepiColombo will investigate these regions to help us better understand this mysterious
planet based on NASA's Messenger mission data. Bepi Colombo will be the first mission in
history to send two ships simultaneously to Mercury, and we hope it will help us reveal
all the secrets this planet has for us.