On June 15, the European Space Agency’s Solar Orbiter completed its first close passage to the Sun. The spacecraft was 77 million kilometers (47.8 million miles) from the surface of our star, which is about halfway between the Earth and the Sun. This is just the beginning – the spacecraft will get closer and closer over the next few years.
The orbiter is expected to take the closest pictures of the Sun yet, which will hopefully be published in about a month. Over the next few weeks, all its scientific instruments will also be tested.
“We have never taken pictures of the Sun from a closer distance than this,” ESA’s Solar Orbiter Project Scientist Daniel Müller said in a statement. “There have been higher resolution close-ups, e.g. taken by the four-meter Daniel K. Inouye Solar Telescope in Hawaii earlier this year. But from Earth, with the atmosphere between the telescope and the Sun, you can only see a small part of the solar spectrum that you can see from space.”
Solar Orbiter has now officially entered the cruise phase, which will last until November 2021 when the science phase begins in full. The craft will pass Venus and Earth several times until it is placed on an orbit that will take it as close as 42.5 million kilometers (26.4 million miles). The months between now and then will allow the suite of instruments to be tested as well as preliminary measurements to be collected.
“This is the first time that our in-situ instruments operate at such a close distance to the Sun, providing us with a unique insight into the structure and composition of the solar wind,” says Yannis Zouganelis, ESA’s Solar Orbiter Deputy Project Scientist. “For the in-situ instruments, this is not just a test, we are expecting new and exciting results.”
Solar Orbiter won’t get as close to the Sun as NASA’s Parker Solar Probe (which will get seven times closer), but it will be the closest camera that we have ever sent towards the star. The reason why Parker is not equipped with a camera to look at the Sun is both simple and mind-blowing. The energy of the Sun at that close of a distance will literally cook the spacecraft if it can penetrate the heat shield. And a camera is a nice big hole with a lens in front.
Solar Orbiter will pass Venus several times, using the gravity of the planet to change the inclination of its orbit. This will take the spacecraft to above and below the plane of the Solar System, allowing the first photographs of the Sun's poles.
The spacecraft was only launched in February but you'll be excused if that feels like years ago.