When the spacecraft reaches its orbit around the sun, it is only 42 million km from the red-hot globe, compared to the earth's 150 million km. The probe's heat shield must withstand more than 500 degrees heat.

Closer to the solar wind

The sun is constantly blowing out a whirlwind of charged particles at speeds up to a thousand kilometers per second, and the solar wind fills the entire solar system. Around the planets, the solar wind then creates space weather. With Solar Orbiter, you measure parking equipment much closer to the source of the solar wind.

- We want to know how the solar wind drives the whole system. From the probe we can observe the surface with a telescope. If, for example, there would be an eruption on the surface, we can then measure the effects of the eruption in the solar wind, says Andris Vaivads, professor of space physics at KTH and involved in the project.

Heat shield should protect against the sun

So close to the sun, the sunlight is 13 times more intense than the earth, and there are strong eruptions of radiation from the sun's atmosphere. All in all, the environment is very inhospitable, and the probe's heat shield is absolutely necessary to protect the equipment. But the heat shield must also have openings so that, for example, the telescope can be used at all.

- That construction has been a very big challenge, says Vaivads. Parts of antennas also protrude behind the shield and become heated.

US NASA already has a solar probe in orbit, the Parker Solar Probe. It is still much closer to the sun but it has no telescope on board. ESA's Solar Orbiter will be able to walk in a higher orbit that makes it possible to study the polar regions of the sun.

Want to study the sun's activity

The reason for this curiosity is that the magnetic poles of the sun change places with each other on average every eleven years. The north becomes south and vice versa, and before any such reversal, the activity of the sun increases. When the sun receives strong outbreaks, there is always a risk that they reach the earth and in the worst case, damage both satellites and infrastructure on the ground.

Interest in how the solar system's engine works has long been great, and the researchers would like to know more.

- It's always better for us to know how things work, says Andris Vaivads.