Now it's off. The space probe Bepicolombo has begun its journey towards Mercury where it is expected to land in seven years. The European-Japanese project is now seriously underway, and the launch early on Saturday morning Swedish time went according to plan, reports the news agency AP.

The probe will examine both Mercury's surface and its magnetic field. To measure parts of the magnetic field, ESA has turned to Swedish space scientists and engineers from KTH in Stockholm and the Institute of Space Physics in Uppsala and Kiruna.

The researchers have developed an instrument that is somewhat reminiscent of a sewing thread roll. Millimeter thin wire has been rolled up into two separate cylinders.

When the probe arrives at Mercury, the wires will be rolled out and via two metal balls at each end, the voltage differences in the electric field of the planet will be measured.

This is what the instrument that will measure Mercury's electric field looks like. Photo: Tomas Karlsson KTH

The sun's stress

Because of Mercury's proximity to the sun and the huge attraction of the star, it takes more energy to send a probe to Mercury than it does to Pluto. In addition, the planet is characterized by strong solar winds and massive temperature differences.

- You have to make sure you use materials that reflect enough sunlight so that there is no overheating. Another major challenge has been to create a mechanism that can output these threads in a good way. It really has to be right, you can't fix anything when the probe is gone at Mercury just, says Tomas Karlsson, associate professor of Space and Plasma Physics at KTH and one of the researchers behind the project.

15 years of work in space

Now the probe is going away with the instrument that Thomas Karlsson and his colleagues have been working on for fifteen years.

- The great nervousness comes first with the launch itself. It is usually said that it is not rocket research, but in this case it is. So I will follow this closely and nervously early on Saturday morning, says Tomas Karlsson.

Although they do not become completely unemployed during the probe's seven-year journey, it is not until it has arrived that the workload is gaining momentum. The researchers then have to control the instrument they have developed and plan which measurements to take.

- It is really amazing, the thoughts fizzle when you think that something you have been with and fingered will soon be around Mercury, says Tomas Karlsson.

The Swedish researchers have collaborated with researchers from the University of Tohoku in Japan.