On June 16, 2025, the European Space Agency (ESA) unveiled groundbreaking images of the Sun’s outer atmosphere, the solar corona, thanks to its Proba-3 mission. This mission achieved an incredible feat—two satellites flying in perfect formation to create an artificial total solar eclipse. The resulting images provided an unprecedented look at the Sun’s corona.
Proba-3: Creating an Artificial Solar Eclipse
Proba-3, ESA’s cutting-edge mission, uses two synchronized satellites—the Coronagraph and the Occulter—that fly just 150 meters apart. Together, these spacecraft can generate an artificial total solar eclipse in space by positioning the Occulter in front of the Sun. This configuration casts a tiny 8-centimeter shadow on the Coronagraph’s ASPIICS, allowing it to capture detailed images of the Sun’s faint corona without the interference of its bright central disk. Unlike natural eclipses, which last only a few minutes and occur only once or twice a year, Proba-3’s artificial eclipses can last for up to six hours, providing scientists with a sustained view of the Sun’s outer atmosphere.
The mission’s success lies in the precision required to maintain this formation flying. The satellites are able to maintain their positions with millimeter-level accuracy, an achievement made possible by advanced technology, including optical cameras, laser systems, and inter-satellite radio links. The satellites operate autonomously, without any help from ground controllers, ensuring the formation is stable throughout the mission.
Unveiling the Mysteries of the Solar Corona
For decades, scientists have been intrigued by the solar corona, a region of the Sun’s atmosphere that reaches temperatures in excess of one million degrees Celsius—much hotter than the Sun’s surface. Studying this region is crucial for understanding solar phenomena such as solar wind and coronal mass ejections (CMEs). These powerful bursts of particles can affect space weather and, on occasion, disrupt communications, power grids, and satellite systems on Earth.
Proba-3’s images, captured by the ASPIICS coronagraph, offer a closer look at the corona, providing scientists with insights into the Sun’s dynamic behavior. The images taken on May 23, 2025, reveal intricate loops of plasma extending from the Sun’s surface, similar to the structures seen after solar flares. These images mark a significant advancement in solar research, as they capture the solar corona with greater detail and clarity than traditional coronagraphs.
Solar Winds and Space Weather Insights
The ability to observe the solar corona in such detail has broad implications for understanding space weather. Coronal mass ejections (CMEs) are a key area of focus. These explosive solar events release vast amounts of energy into space, impacting Earth’s magnetic field and potentially leading to geomagnetic storms. Proba-3’s observations help scientists gain a better understanding of CMEs and solar wind, which could improve our ability to predict space weather events and their effects on Earth.
Also, the ASPIICS coronagraph, Proba-3 carries other scientific instruments such as the Digital Absolute Radiometer (DARA) and the 3D Energetic Electron Spectrometer (3DEES). These instruments contribute to a comprehensive study of the Sun’s energy output and the behavior of energetic particles in Earth’s radiation belts, enhancing our understanding of the Sun’s impact on our planet.
A Leap in Autonomous Space Technology
Proba-3’s success in achieving precise formation flying without ground intervention is a testament to the advancements in autonomous space technology. ESA’s mission manager, Damien Galano, expressed excitement over the achievement: “Having two spacecraft form one giant coronagraph in space allowed us to capture the inner corona with very low levels of stray light in our observations, exactly as we expected.”
While the mission is still in its commissioning phase, the results so far show the potential of this technology for future space missions. The satellites’ autonomous formation flying was achieved through a combination of sensors, star trackers, optical cameras, and laser systems. As the mission progresses, ESA aims to achieve full autonomy, removing the need for regular monitoring from Earth.
