On the 4th of December 2024, the European Space Agency (ESA) will launch two spacecraft into space, with the goal of creating an artificial solar eclipse – the mission name is Proba-3.
The aim is that this artificial eclipse will help researchers to study the sun, specifically for information on the sun’s atmosphere – its corona: the corona’s temperature, how it expands into space, and the creation of solar wind. Mission manager, Damien Galano, said “It will be the closest to the sun we have observed the corona in visible light”.
The spacecraft will be launched on an Indian PSLV-XL rocket by the Indian Space Research Organisation (IRSO), then will transition into an elliptical orbit around Earth, ranging from 600-60,000 km away from the surface. To recreate the moon covering the sun in a total solar eclipse, one of the spacecraft, named the Occulter, has a 1.4 metre-wide disc attached to it. This disc is made out of carbon fibre and plastic, and will block the sun’s surface from the viewpoint of the second spacecraft, the Coronagraph, flying around 150 metres behind it with a camera focused on the Occulter.
Over the course of the mission, lasting two years, over 1000 eclipses are scheduled, each lasting six hours. They will occur when the spacecraft are on the end of the elliptical orbit furthest away from Earth, to reduce any disrupting effects coming from Earth’s gravitational pull.
As well as enabling the most detailed study of the solar corona, the mission will also demonstrate the possibilities of highly precise formation flying in space, with the precision aiming to be down to a single millimetre. This is done through sensors on the spacecraft which enables ground teams to track their location in space. The Occulter fires a laser to a retroreflector on the Coronagraph; this is just one of the many technologies involved in the precision of position tracking and adjusting. Furthermore, the Occulter has 12 nitrogen thrusters which can keep its position relative to the second spacecraft accurate to one millimetre. The thrusters are so sensitive, they can eject 50 times less force than a human breath to keep the separation so precise.
This precision is revolutionary; a lead engineer on the mission from the US says that “Up until now, we’ve only been able to do a centimetre precision or more. This is ten times better.” It’s thanks to contributions from 29 companies from 14 different countries that this mission was made a reality, led by the Spanish engineering and technology group, SENER. Mission control will be based in ESA’s European Space Security and Education Centre in Redu, Belgium.
