ESA’s Proba-3 mission has revealed its first detailed images of the Sun’s outer atmosphere, known as the corona. Using two satellites flying in precise formation, Proba-3 creates an artificial total solar eclipse, which is something never done before in space.
By blocking the Sun’s bright disc, the mission gives scientists a rare and clear look at this mysterious region, which plays a key role in solar activity. Dietmar Pilz, ESA’s Director of Technology, Engineering and Quality, called the results “stunning images [that] validate our technologies in what is now the world’s first precision formation flying mission.”
Two Satellites, One Eclipse
The Proba-3 satellites, named the Coronagraph and the Occulter, fly just 150 metres apart. Thanks to advanced positioning technology, they keep this distance down to a millimetre, without any control from the ground.
When they align with the Sun, the Occulter blocks sunlight for the Coronagraph, casting a small shadow onto its onboard camera system. By carefully blocking the Sun’s direct light, the system gives ASPIICS a much clearer view of the corona, something that’s normally hidden by the Sun’s brightness.
Unlocking the Secrets of the Corona
These new images help scientists study solar wind and powerful eruptions called coronal mass ejections, or CMEs. While these can cause beautiful auroras, they can also damage satellites, power grids, and communications on Earth. A major CME disrupted systems in May 2024.
According to ESA project scientist Joe Zender, “ASPIICS will contribute to unravelling long-lasting questions about our home star.”
A Hotter Layer Above a Cooler Surface
It’s long puzzled scientists how the Sun’s corona ends up far hotter than its surface. Despite sitting above the Sun’s outer layer, the corona can reach temperatures of over a million degrees Celsius.
ASPIICS is giving scientists a fresh look at the corona, helping them pick out details that were once too faint to see. By cutting down the excess light that usually floods this kind of observation, it’s making it possible to track features that might explain why this outer layer is so unexpectedly hot. The first images are already offering new insights into this enduring solar mystery.
Gathering Data from Every Angle
ASPIICS creates each full image by combining three different exposures. This method reveals both the brighter and dimmer parts of the corona in one shot. The images are processed by a team at the Royal Observatory of Belgium, which also coordinates what the instrument should focus on each time.
Andrei Zhukov, who leads ASPIICS from the observatory, said, “I was absolutely thrilled to see the images, especially since we got them on the first try.” He added that the team is now aiming to “extend the observation time to six hours in every orbit.”
Formation Flying in Space
The success of Proba-3 also marks a major step in spaceflight technology. The mission has shown that two spacecraft can fly together with incredible accuracy to act like a single instrument.
Mission manager Damien Galano explained, “We have already achieved precise formation flying with unprecedented accuracy.” He noted that this progress has come even before the mission reaches full autonomy, which will allow it to operate without routine monitoring from the ground.
Better Models for Space Weather
The high-quality images from Proba-3 are also changing the way scientists model the Sun’s activity. Until now, researchers had to rely on rare eclipse photos to study the corona close to the Sun. Now, they can get a steady stream of data.
“Current coronagraphs are no match for Proba-3,” said Jorge Amaya, ESA’s Space Weather Modelling Coordinator. He added that new data is helping refine simulations, including those made with KU Leuven’s COCONUT software.
A European Team Effort
The Proba-3 mission is led by ESA and managed by Spain’s Sener. It brings together more than 29 companies from 14 countries. Major partners include GMV and Airbus Defence and Space in Spain, along with Redwire Space and Spacebel in Belgium.
Proba-3 launched on 5 December 2024 aboard a PSLV-XL rocket from India’s Satish Dhawan Space Centre. With this mission now underway, a new era of solar science is just beginning.
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