ESA Satellites Create First Artificial Total Solar Eclipse in Space

The European Space Agency’s (ESA) historic Proba-3 mission, designed to create and study solar eclipses in orbit, has successfully made its first artificial eclipse in space, and the images are breathtaking.

The Proba-3 mission comprises two satellites expertly engineered to operate as a single spacecraft using onboard positioning technology unlike anything that has ever been sent to space, as lead Proba-3 engineer Steven Buckley of Onsemi explained to PetaPixel last year. Buckley worked on the project for over seven years, ensuring that the sensors and algorithms could align Proba-3’s coronograph and occulter spacecraft with millimeter-level precision while traveling at a speed of 22,000 miles per hour.

All that work has paid off in a big way, as the Proba-3 team successfully created the first-ever artificial solar eclipse in orbit. The resulting photographs provide key insights and scientific data that will help people gain a deeper understanding of the Sun and its atmosphere.

Solar eclipses on Earth are a significant opportunity for scientists to study the Sun’s corona, its outer atmosphere, which helps improve the understanding of the coronal mass ejections (CMEs) that drive space weather and have significant implications for life on Earth. While CMEs help create beautiful auroras, they can also disrupt vital communications technologies on Earth.

To create an artificial solar eclipse, Proba-3’s Occulter is precisely positioned between the Sun and the Coronagraph spacecraft. Separated by about 150 meters (around 490 feet), the pair of spacecraft remain aligned for six hours within one millimeter of perfection, ensuring that the occulter perfectly covers the Sun for the coronograph spacecraft and its imaging instruments.

The Proba-3 Coronograph features an optical instrument, Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun (ASPIICS) that captures photos of the solar corona, which is visible when the Sun is entirely blocked, much like it is during a natural total solar eclipse on Earth.

“Many of the technologies which allowed Proba-3 to perform precise formation flying have been developed through ESA’s General Support Technology Programme, as has the mission itself. It is exciting to see these stunning images validate our technologies in what is now the world’s first precision formation flying mission,” says Dietmar Pilz, ESA Director of Technology, Engineering and Quality.

‘This image shows observations in the coronal green line – a spectral line emitted by iron atoms that lost half of their electrons due to extremely high temperatures. This allows us to see the hottest contents of the corona, at up to 2 million degrees. On the upper left side, a hot loop can be seen extending from the Sun’s surface into the corona, a structure which generally appears following a solar flare.’

Credit: ESA/Proba-3/ASPIICS

ASPIICS did a remarkable job capturing the solar corona. These images, alongside the many to come as Proba-3 creates additional artificial eclipses in orbit, will help scientists untangle some of the Sun’s biggest mysteries, including why its fiery corona, which reaches temperatures above a million degrees Celsius, is so much hotter than the Sun’s surface itself.

Not only can Proba-3 create eclipses at will — something scientists certainly cannot do on Earth — the imager avoids the issues of unpredictable weather and atmospheric distortions. ASPIICS can see in incredible detail and detect fainter solar features than other coronographs.

“Seeing the first data from ASPIICS is incredibly exciting. Together with the measurements made by another instrument on board, DARA, ASPIICS will contribute to unravelling long-lasting questions about our home star,” says Joe Zender, Proba-3 project scientist.

DARA, which is the Digital Absolute Radiometer, measures solar irradiance, or the amount of energy the Sun emits at a specific time. A third instrument aboard Proba-3, the 3D Energetic Electron Spectrometer (3DEES), detects electrons in Earth’s radiation belts.

“I was absolutely thrilled to see the images, especially since we got them on the first try,” says Andrei Zhukov, Principal Investigator for ASPIICS at the Royal Observatory of Belgium. “Now we are working on extending the observation time to six hours in every orbit.”

“Each full image — overing the area from the occulted Sun all the way to the edge of the field of view — is actually constructed from three images. The difference between those is only the exposure time, which determines how long the coronagraph’s aperture is exposed to light. Combining the three images gives us the full view of the corona,” Zhukov continues.

The scientist says that the “artificial eclipse” images are “comparable with those taken during a natural eclipse.” However, the difference is that the Proba-3 mission creates an eclipse every 19.6 hours, whereas total solar eclipses occur on Earth once or rarely, twice a year. Furthermore, totality during a natural eclipse lasts just a few minutes, whereas Proba-3 can maintain its artificial eclipse for up to six hours.

“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,” says Proba-3 mission manager Damien Galano.

“Although we are still in the commissioning phase, we have already achieved precise formation flying with unprecedented accuracy. This is what allowed us to capture the mission’s first images, which will no doubt be of high value to the scientific community.”


Image credits: European Space Agency