Proba-3 Made an Artificial Eclipse to Watch the Solar Wind

ESA's Proba-3 mission has reported its first science results from an arrangement that sounds like a trick until its measurement purpose is clear: two spacecraft fly in formation so one can create an eclipse for the other. In its 13 April 2026 report, ESA says the Occulter blocks direct sunlight while the Coronagraph carries ASPIICS, the instrument observing the Sun's inner corona.

The artificial eclipse lasts about five hours. With the Occulter between the Sun and the Coronagraph, ASPIICS can observe down to 70,000 kilometres above the Sun's surface and take one or two images per minute. Those images are combined into videos rather than treated as isolated snapshots. By the time of ESA's report, Proba-3 had produced 57 artificial eclipses and more than 250 hours of high-resolution coronal video.

The useful engineering story is the division of labour. One spacecraft blocks the direct light; the other records the much fainter structures around it. The value of the formation is therefore not just having two spacecraft in the same place. It is holding them in the geometry required to create a long, close view of the inner corona.

The first result concerns the slow solar wind. ESA reports that researchers tracked plasma blobs associated with it moving at 250 to 500 km/s in the inner corona. Earlier work cited in the report had put slow-wind speeds close to the Sun at around 100 km/s. ESA describes the observed blobs as three to four times faster than expected.

The qualification matters. This is not a claim that all slow solar wind travels at 250 to 500 km/s, nor that Proba-3 has settled why the wind accelerates. ESA describes measurement uncertainties, a limited first dataset and further comparisons with models. Most of the collected data still had to be analysed, and the source calls the first dataset the beginning of a longer investigation.

That leaves the mission in an interesting middle state. The formation-flying method has produced the observing time and proximity the instrument was designed to obtain. The early observations are strong enough to challenge an expectation, but not enough to close the scientific question. The hardware result and the scientific result belong together without being confused: one demonstrates access to a difficult view; the other is an initial interpretation of what that view contains. Proba-3's next step is the less cinematic one ESA names—more data, more analysis and comparison with models.