In March, the Coronagraph and Occulter spacecraft successfully flew 150 meters apart, holding their position for hours without ground control. This precise alignment allowed the 1.4-meter disc on the Occulter to block the Sun's bright surface for the Coronagraph's ASPIICS instrument, casting an 8 cm shadow that enabled uninterrupted imaging of the corona.
Developed by a consortium led by Belgium's Centre Spatial de Liege, ASPIICS-short for Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun-uses a 5 cm aperture to detect faint coronal features previously obscured by stray light. These observations are vital for studying solar wind and coronal mass ejections (CMEs), phenomena that affect Earth's technology infrastructure, as seen during the major solar activity in May 2024.
Dietmar Pilz, ESA Director of Technology, Engineering and Quality, stated: "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."
The Sun's corona, mysteriously hotter than its surface, remains a focal point for solar research. ASPIICS offers unprecedented detail by imaging the corona close to the solar limb. Together with Proba-3's DARA instrument, which measures total solar irradiance, and 3DEES, which tracks high-energy electrons in Earth's radiation belts, the mission aims to deepen scientific understanding of solar dynamics.
Principal Investigator Andrei Zhukov of the Royal Observatory of Belgium shared: "I was absolutely thrilled to see the images, especially since we got them on the first try." He added that the team aims to extend eclipse observation durations to six hours per orbit. The ASPIICS Science Operations Centre, also at the Royal Observatory, compiles images by combining three exposures of varying lengths to achieve complete views of the corona.
Unlike fleeting natural eclipses, Proba-3's orbital configuration allows these artificial events to occur every 19.6 hours, lasting up to six hours each. Mission manager Damien Galano emphasized the low stray light levels achieved and noted that the system's autonomous formation flying was monitored but not manually corrected-one final step away from full autonomy.
Beyond imaging, Proba-3's data is enhancing digital eclipse simulations. The mission's observations are refining solar corona models like COCONUT, developed by KU Leuven, integrated into ESA's Virtual Space Weather Modelling Centre. Jorge Amaya, ESA's Space Weather Modelling Coordinator, said: "Current coronagraphs are no match for Proba-3, which will observe the Sun's corona down almost to the edge of the solar surface."
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