The European Proba-3 spacecraft pair has created its first artificial solar eclipse.

Total solar eclipses are not only awe-inspiring celestial phenomena — they are also crucial scientific opportunities. These rare events allow researchers to investigate the solar corona, the Sun’s ultra-hot outer atmosphere, and study its dynamics. Since solar eclipses don’t occur frequently, the European Space Agency (ESA) has initiated the Proba-3 mission to create artificial eclipses — and the first images have just been released.

This artificial eclipse takes place in orbit between two specially designed spacecraft flying in precise formation. Separated by 150 meters (492 feet), the two spacecraft synchronize for several hours at a time to observe the Sun. Their alignment is accurate down to the millimeter, thanks to cutting-edge navigation and positioning technology.

---

The spacecraft facing the Sun is the Occulter, built to block the solar disk for the second craft, the Coronagraph, which is positioned Earth-side. The Occulter casts a narrow shadow just 8 centimeters (3.15 inches) wide onto the ASPIICS optical instrument on the Coronagraph.
“I was absolutely thrilled to see the images, especially since we got them on the first try,” Andrei Zhukov, Principal Investigator for ASPIICS at the Royal Observatory of Belgium, said in a statement. “Now we are working on extending the observation time to six hours in every orbit.”

Studying the corona through this method enables scientists to gain deeper insight into the solar wind’s origin and the release of coronal mass ejections — both of which can lead to brilliant aurorae and have the potential to disrupt Earth-based technology. Thanks to Proba-3, scientists now have access to a daily artificial eclipse.

“Our ‘artificial eclipse’ images are comparable with those taken during a natural eclipse.” Zhukov continued. “The difference is that we can create our eclipse once every 19.6-hour orbit, while total solar eclipses only occur naturally around once, very rarely twice a year. On top of that, natural total eclipses only last a few minutes, while Proba-3 can hold its artificial eclipse for up to 6 hours.”

---

Coronagraphs have been widely used in astronomical instruments. Typically, they use physical masks or stickers to block the Sun’s (or other stars’) light. However, this often leads to unwanted optical artifacts that make it challenging to observe the lower regions of the corona.

“In a more ‘traditional’ coronagraph, you can end up with a bright rim in the part of the image is that around the edge of the occulting disc. This effect is caused by vignetting and diffraction of light entering the telescope. To improve the image on the sections nearest the occulting disc – you must put your occulting disc as far away from the entrance aperture of your telescope as possible,” Professor Lucie Green from University College London, told last year. Green is working on the MESOM mission, which aims to build on Proba-3 and utilize the Moon to generate more regular eclipses.

Although Proba-3’s eclipse views don’t match the exact proximity of natural eclipses, the mission compensates with its capacity for frequent and extended observations. Its highly elliptical orbit provides the time needed for meticulous positioning. A combination of technologies — including GPS, star trackers, autonomous navigation, and laser systems — enables the two spacecraft to maintain millimeter-level precision during flight.

---

“Many of the technologies which allowed Proba-3 to perform precise formation flying have been developed through ESA’s General Support Technology Programme, as has the mission itself. It is exciting to see these stunning images validate our technologies in what is now the world’s first precision formation flying mission,” Dietmar Pilz, ESA Director of Technology, Engineering and Quality, commented.

This marks only the beginning for Proba-3. The mission promises more groundbreaking science and valuable insights into our star in the near future.

---