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The European Space Agency (ESA) has launched its mission to the planet Mercury from its spaceport near the equator in Kourou, French Guyana, on October 20. My involvement in the mission means that I will be anxiously following the journey of spacecraft out a series of tricky maneuvers, culminating in its final approach to Mercury in 2025.
The mission comes from a group of scientists who have come to ESA, and 18 years after ESA approved the project as a "cornerstone" mission. This is the category of world-class, scientifically excellent missions requiring significant new technology development. Previous ESA cornerstone missions include the Rosetta comet mission and the LISA Pathfinder gravitational wave observatory.
But why Mercury? It is a puzzling planet. NASA's MESSENGER orbiter (2011-2015) revealed many reasons why scientists are keen to learn more about it. These include the planet's abnormally large core – we do not know why it is still moving and able to generate a magnetic field, unlike that of Mars or Venus. Another mystery is the abundance of (largely unidentified) volatile substances at its surface. Mercury now is.
The Rocket Science
BepiColombo's initial race orbiting the Earth for checkouts will be an elliptical orbit about the sun. This will begin with the earth's orbit. But early in 2019, it will be more than a few years ago. It will then move back to Earth in April 2020.
At that time, it will make a "gravity-assist" flyby – using the Earth's gravity to swing itself inwards towards Venus. There will also be a gravity-assist flyby of Venus when it gets there in 2020, followed by another one in 2021 to send it to Mercury. Then, there will be a series of six similar flybys of Mercury in 2021-2025, needed to ensure that the spacecraft eventually ends up in 2025.
Each flyby, shown in the above animation, has to be executed perfectly. Things could go wrong, especially during the launch, but I have full confidence in the abilities of ESA in Darmstadt, Germany.
Stacked Spacecraft
The mission, which is named in memory of Giuseppe (Bepi) Colombo, who is a first-time joint venture between ESA and its Japanese counterpart, JAXA.
The stacked spacecraft carries two orbiters. ESA's is a two-meter-long unit, referred to as the Mercury Planetary Orbiter, DFO. I suspect that after it begins to orbit Mercury, it will be inherited from BepiColombo, or maybe just Bepi. The Japanese orbiter is smaller, and its mass is about a quarter of ESA's orbiter. Originally called the Mercury Magnetospheric Orbiter, MMO, in June it was awarded the name Mio, which carries the connotations of safe navigation. During the cruise to Mercury, the European Union and the European Union.
On the other side of the orbit is the Mercury Transfer Module, MTM. This is operated by ESA, and provides the propulsion to take the stacked spacecraft to its Mercury orbit. It has a 7.5-meter-long "wing" of solar panels, whose job is to turn sunlight into electricity to power its "ion drive." stripping its atoms of electrons). This technique can provide much more thrust for the mass of fuel than standard chemical rockets.
The sun's enormous gravity means that it is needed to get a stable orbit about Mercury than would be needed to send the same spacecraft to vastly distant Pluto. Because of this, the time will be operating in the future.
Unfortunately, the stacked configuration of the combined spacecraft impedes its ability to do science during the planetary flybys. Some scientific data will be collected, but the best pictures will be produced by the selfie-cams mounted on the MTM.
Arriving at Mercury
On arrival at Mercury in late December 2025, the transfer module will be detached. Mio, spinning at 15 revolutions per minute for stability, will then be released on a strongly elliptical orbit about Mercury. As soon as this happens, JAXA will take over Mio operations and guide it through its tasks, studying the planet's magnetic field and the associated space environment.
ESA's orbiter will then be replaced by the sunshield, its last impediment, and use its own chemical thrusters to achieve a closer, more circular, orbit about Mercury. From there it will be possible to study the planet by using an assortment of cameras and other instruments. This should pin down the composition and geological history in much better than the smaller and less complex MESSENGER. The orbiter will also carry a magnetometer so that it will be able to report to the world in the future.
It's exciting to think that BebiColombo can transform our knowledge of Mercury in just a few years. And while you wait, from October 23, you will be able to listen to some beautiful, evocative music that the planet has gotten as part of the Planets 2018 project. This was set up to commemorate the centenary of Gustav Holst's Planets Suite with music inspired by the science of the planets.
This article was originally published on The Conversation by David Rothery. Read the original article here.
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