Belgian Satellites Capture Rare Double Solar Eclipse

While millions across Europe watched the total solar eclipse of 12 August from the ground, a pair of largely Belgian-built satellites witnessed something far rarer from orbit: a unique double eclipse, captured as the Moon crossed their field of view while the spacecraft simultaneously held their own artificial eclipse. The extraordinary imagery, released by the European Space Agency, offers scientists an unprecedented opportunity to validate their observations of the Sun’s corona.

The Proba-3 mission, a collaboration of 15 ESA countries led by Spanish company Sener, consists of two satellites flying 150 metres apart at an altitude of 60,000 km above Earth. The Occulter spacecraft acts as an artificial Moon, blocking the Sun for the Coronagraph spacecraft, which carries the ASPIICS coronagraph instrument. According to VRT NWS, the satellites are largely of Belgian manufacture, built and tested at Redwire Space in Kruibeke, East Flanders, and controlled from the ESA centre in Redu in the Belgian Ardennes.

A Once-in-a-Lifetime Celestial Alignment

On the morning of 12 August, hours before the Moon’s shadow swept over Earth, our closest celestial neighbour crossed Proba-3’s field of view while the satellites were holding their 65th artificial eclipse. Because Proba-3 was closer to the Moon than Earth was, the double eclipse lasted 8 minutes 40 seconds - significantly longer than the maximum 2 minutes 18 seconds of totality observed on the ground just off the coast of Iceland.

“It’s not really a video, but a sequence of individual photos,” explained Stijn Ilsen, space engineer at Redwire Space who has worked on the project since 2008. “It goes very fast. On Earth you see the Moon move very slowly during a solar eclipse, but because the satellites fly through space at more than 30,000 kilometres per hour, the Moon passes by super quickly.”

During the almost nine minutes of double eclipse, the ASPIICS coronagraph was essentially free from parasitic light - normally produced by diffraction of the solar disc light on the edge of the Occulter spacecraft. This allowed scientists to calibrate the optical performance of the instrument and briefly observe the corona in the best possible conditions, as detailed in the ESA video release. The sequence of images captured by the mission is also available on YouTube.

Belgian Engineering at the Heart of the Mission

The Proba-3 satellites represent a significant Belgian achievement in space engineering. Assembled and tested at Redwire Space in Kruibeke, the spacecraft also carry onboard computers supplied by the same company - described by Erik Masure of Redwire Space as the “brain” of the two satellites. The ASPIICS coronagraph was developed under the leadership of the Centre Spatial de Liege, with scientific research led by the Royal Observatory of Belgium.

Ilsen, who has dedicated nearly two decades to the project, described the engineering challenge: “I’ve been working on it since 2008. It was a long haul and extremely complex. Never before had 2 satellites been able to fly in space with millimetre-level accuracy relative to each other.” The satellites were launched on 5 December 2024 from the Satish Dhawan Space Centre in India aboard an ISRO PSLV-XL rocket.

Scientific Significance Beyond the Spectacle

While the double eclipse produced spectacular imagery, its true value lies in what it enables scientists to learn. As Ilsen noted, “Because you have both an artificial solar eclipse in space and a real one on Earth at the same time, you can compare the images and measurements of both. This way you can check whether what we normally measure with Proba-3 is actually correct.”

The mission’s ability to create artificial eclipses on demand - up to six hours per orbit - allows continuous observation of the solar corona, the Sun’s outer atmosphere where space weather originates. This capability has already yielded significant discoveries. According to TechTimes, Proba-3’s first published science results in The Astrophysical Journal Letters (March 2026) found that slow solar wind in the inner corona moves 3-4 times faster than existing models predicted, forcing a rewrite of space weather forecasts.

Andrei Zhukov, principal investigator for ASPIICS at the Royal Observatory of Belgium, explained how the mission’s artificial eclipses complement natural ones: “Our artificial eclipse images are comparable with those taken during a natural eclipse. The difference is that we can create our eclipse once every orbit, which takes 19 hours and 40 minutes, while total solar eclipses only occur naturally around once, very rarely twice a year.”

A Prediction Validated

The double eclipse was not the only remarkable aspect of Proba-3’s August observations. Two weeks before the natural eclipse, the mission captured an artificial eclipse that served as a remarkably accurate prediction of what the corona would look like on 12 August. Because it takes the Sun two weeks to rotate halfway around its axis, horizontally mirroring the image taken on 30 July provided a forecast of the corona’s structure during the natural eclipse, as explained in the ESA article on the mission’s modelling capabilities.

What’s Next for Proba-3

The double eclipse is a once-in-a-lifetime event for the mission. Before Proba-3 ends, it will experience only two partial eclipses during the next two on-ground total eclipses - on 2 August 2027 and 22 July 2028 - during which the Moon will pass through the ASPIICS field of view but will not cover the full solar disc.

For the scientists and engineers behind the mission, the August observations represent a culmination of years of work and a validation of the technology. As Ilsen reflected on the mission’s potential impact: “I understand this could turn the world of solar physics on its head.” With the ability to create artificial eclipses on demand and now the rare opportunity to compare those observations directly with a natural eclipse, Proba-3 is positioned to transform our understanding of the Sun and improve our ability to forecast the space weather that affects modern technology on Earth.