17/12/2025
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It has been a busy year for the European Space Agency’s Proba-3 mission. The satellite duo has already created more than 50 artificial solar eclipses in orbit since the mission operations began less than a year ago. The resulting data confirm Proba-3’s ability to provide the missing puzzle piece in our observations of the Sun’s enigmatic atmosphere – the corona.
Since its launch in December 2024, the Proba-3 satellite duo has claimed not one, but two world firsts – the first precise formation flight, setting the mission up for the first artificial solar eclipse in orbit.
The hundreds of hours of observations that followed leave no doubt that Proba-3 delivers the missing data needed to fill the current observation gap, providing insights into the inner regions of the Sun’s corona.
Our eyes on the inner corona
Until now, space-based instruments were only able to reliably image the solar disc and the outer region of the corona, and the full corona could only be observed from Earth during the short periods of total eclipses. Although they are not entirely impossible to make, any observations of the inner coronal region so far have been infrequent or inconsistent, leaving us with an observation gap.
“Thanks to a set of onboard positioning technologies that allow the Proba-3 duo to create a solar eclipse in orbit, the mission is delivering on its promise to fill this gap,” explains Proba-3 mission manager Damien Galano.
In this largely unexplored region of the solar corona, the solar wind gains speed before streaming out into the Solar System, eventually reaching both our spacecraft and Earth. It is also here that most coronal mass ejections (CMEs) originate. By capturing detailed images, Proba-3 is enabling scientists to advance their understanding of how the solar wind accelerates and how CMEs are triggered.
The time-lapse animation below captures a CME in the top right, combining observations made over one hour and a half on 16 July by three different European instruments aboard different missions: the Sun’s disc and low corona (artificially coloured in yellow), as captured by an extreme-ultraviolet telescope (SWAP) aboard Proba-2; the outer corona (in red) observed by the LASCO C2 coronagraph aboard SOHO; and the inner corona (in green), imaged in detail by Proba-3’s ASPIICS coronagraph, filling the gap.
Andrei Zhukov from the Royal Observatory of Belgium, Principal Investigator for the ASPIICS coronagraph aboard Proba-3, comments: “You can see the CME forming at the edge of the solar disc, captured by Proba-2. It extends into the inner coronal region, which is now visible to us thanks to Proba-3, before reaching the high corona observed by SOHO. The continuity with which we can now observe the CME structure extend outwards from the Sun is incredible.”
Total solar eclipse on demand
“Our artificial eclipse images are comparable with those taken during a natural eclipse,” adds Andrei. “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. 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.”
Joe Zender, Proba-3 project scientist, adds: “So far, the mission’s observation time has amounted to about 250 hours across 50 orbits. This means these past few months alone deliver the same amount of data we could get from 6000 total eclipse campaigns on Earth.”
A year of Proba-3
One year ago, on 5 December 2024, the two Proba-3 spacecraft launched to orbit, where they were carefully separated six weeks later. In March this year, the satellite duo performed its first autonomous formation flight.
Only a month later, the mission has achieved its ambitious goal – for the first time, two spacecraft in orbit aligned in formation with millimetre precision and maintained their relative position for several hours without any control from the ground.
Demonstrating the degree of precision achieved, the two spacecraft that make up the Proba-3 mission – the Coronagraph and the Occulter – use their formation flying time to create artificial solar eclipses in orbit.