Artificial solar eclipse engineered in Europe offers new look at Sun

Two satellites equipped with European tech have delicately pulled off an artificial solar eclipse — giving scientists unmatched views of the Sun’s scorching corona.

The European Space Agency (ESA) developed the probes alongside more than 40 space tech firms. Among them are a trio of startups, which contributed several key technologies for the mission: sensors for solar tracking, light detectors to fine-tune positioning, and software that orchestrated the satellites’ intricate flight path.

Launched from India’s Satish Dhawan Space Centre last year, the expedition — Proba-3 — could mark a new era for solar science.

The pair of satellites orbits the Earth in formation, 150 metres apart. One of them, Occulter, acts as the Moon would in a solar eclipse down on Earth. It blocks the Sun, allowing its counterpart satellite, the Coronagraph, to view the Sun’s outer atmosphere or “corona” without being blinded by the intense light. 

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The Sun’s corona is the outermost part of its atmosphere. Surprisingly, it’s far hotter than our star’s surface, sometimes reaching up to 2 million °C. This tumultuous region of superheated, radiative gases is the source of solar storms and coronal mass ejections, which can disrupt telecommunications on Earth — and produce breathtaking Northern Lights displays.

The corona is typically only visible to the naked eye during a total solar eclipse, giving scientists only a brief window to study it. But Proba-3’s achievement could change that. 

“We can create our eclipse once every 19.6-hour orbit, while total solar eclipses only occur naturally around once, very rarely twice a year,” explained Andrei Zhukov of the Royal Observatory of Belgium, which developed the Coronagraph’s main optical sensing instrument ASPIICS. 

While natural total eclipses only last a few minutes, Proba-3 can maintain its artificial eclipse for up to 6 hours. Both satellites can remain perfectly aligned with each other and the Sun to within millimetre precision — all while racing around Earth at a speed of 1 kilometre per second. 

That precision relies on the combined innovations of several European companies. Dutch startup Lens R&D, a graduate of ESA’s business incubator, provided sensors that continuously track the Sun’s position to within fractions of a degree, enabling the delicate choreography of formation flying. 

Meanwhile, engineers at Irish firm Onsemi (formerly SensL) added highly sensitive light detectors called silicon photomultipliers, which measure tiny shifts in the Sun’s shadow across the satellite’s structure to fine-tune their positioning during the eclipse. 

Supporting this hardware is software from Poland’s N7 Mobile, a startup that pivoted from consumer apps to computer systems that control spacecraft. Its code contributes to the probe’s formation control systems. 

All these technologies are part of a European effort to make a six-hour eclipse in orbit not only possible, but repeatable.