ESA Proba-3 Mission Detects Surprisingly Fast Solar Wind

The European Space Agency’s Proba-3 mission has produced its first scientific results, revealing that solar wind structures within the Sun’s inner corona travel three to four times faster than previously estimated by scientists. These findings, published in The Astrophysical Journal Letters, provide new insights into the region where space weather is born.

The discovery was made possible through the use of two satellites flying in an extremely precise formation to create artificial solar eclipses in orbit. Since July 2025, the pair of spacecraft has created 57 artificial eclipses, collecting more than 250 hours of high-resolution video of the corona, which is the atmosphere of the Sun.

This volume of observational data is equivalent to approximately 5,000 total solar eclipse campaigns conducted from Earth. By eliminating the need to wait for natural celestial alignments, the mission allows researchers to carefully track the movement of material from the Sun through the inner corona.

Precision Formation Flying and Instrumentation

Proba-3 utilizes a unique dual-spacecraft system to overcome the limitations of traditional solar observation. One spacecraft, known as the Occulter, acts as an artificial Moon by blocking the direct light of the Sun. This allows the second spacecraft, the Coronagraph, to observe the corona without being blinded by the solar disc.

The Coronagraph is equipped with the ASPIICS instrument, which can observe light scattering off particles as close as 70,000 kilometers from the Sun’s surface. This distance represents one-tenth of the Sun’s radius, a proximity that no other space-based coronagraph can currently achieve.

To generate these views, the Occulter blocks the Sun’s light for approximately five hours at a time. The ASPIICS instrument captures one or two images per minute, which are then combined into videos to reveal movement in the inner corona that was previously impossible to observe.

Filling the Solar Observation Gap

Prior to the launch of Proba-3 in December 2024, space-based instruments could reliably image the solar disc and the outer regions of the corona, but the inner corona remained an observation gap. The only consistent way to view this region was during total solar eclipses seen from Earth.

Natural total solar eclipses occur on average only once every 18 months, and the period of totality lasts for only a few minutes. This made observations of the inner coronal region infrequent and inconsistent.

Proba-3 mission manager Damien Galano stated that 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.

Impact on Space Weather Understanding

The inner corona is a critical region for understanding the dynamics of the solar system. It’s the area where the solar wind gains speed before streaming outward toward Earth and other spacecraft. This region is where most coronal mass ejections, or CMEs, originate.

By capturing detailed imagery of this unexplored region, Proba-3 is enabling scientists to advance their understanding of how CMEs are triggered and how the solar wind accelerates. The mission has already achieved two world firsts, including the first precise formation flight required to establish an artificial solar eclipse in orbit.