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\t\t\t\t\t\t16\/06\/2025<\/span> Today, the European Space Agency\u2019s Proba-3 mission unveils its first images of the Sun\u2019s outer atmosphere \u2013 the solar corona. The mission\u2019s two satellites, able to fly as a single spacecraft thanks to a suite of onboard positioning technologies, have succeeded in creating their first \u2018artificial total solar eclipse\u2019 in orbit. The resulting coronal images demonstrate the potential of formation flying technologies, while delivering invaluable scientific data that will improve our understanding of the Sun and its enigmatic atmosphere.<\/p>\n<\/div>\n Two spacecraft flying as one<\/b><\/p>\n This March, Proba-3 achieved what no other mission has before \u2013 its two spacecraft, the Coronagraph and the Occulter, flew 150 metres apart in perfect formation for several hours without any control from the ground.<\/p>\n While aligned, the pair maintain their relative position down to a single millimetre \u2013 an extraordinary feat enabled by a set of innovative navigation and positioning technologies.<\/p>\n Demonstrating the degree of precision achieved, the two spacecraft use their formation flying time to create artificial total solar eclipses in orbit \u2013 they align with the Sun so that the 1.4 m large disc carried by the Occulter spacecraft covers the bright disc of the Sun for the Coronagraph spacecraft, casting a shadow of 8 cm across onto its optical instrument, ASPIICS.<\/p>\n<\/p><\/div>\n This instrument, short for Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun, was developed for ESA by an industrial consortium led by\u00a0Centre Spatial de Li\u00e8ge, Belgium. When its 5 cm aperture is covered by the shadow, the instrument captures images of the solar corona uninterrupted by the Sun\u2019s bright light.<\/p>\n Observing the corona is crucial for revealing solar wind, the continuous flow of matter from the Sun into outer space. It is also necessary for understanding the workings of coronal mass ejections (CMEs), explosions of particles sent out by the Sun almost every day, especially during high activity periods.<\/p>\n Such events can create stunning auroras in the night sky but also pose serious threats to modern technology. They can significantly disrupt communications, power transmission, and navigation systems on Earth, as they did in May 2024.<\/p>\n<\/p><\/div>\n The coronal images resulting from the first rounds of ASPIICS\u2019s observations offer a glimpse of the valuable data we can expect from this eclipse-making mission.<\/p>\n Dietmar Pilz, ESA Director of Technology, Engineering and Quality, comments: \u201cMany of the technologies which allowed Proba-3 to perform precise formation flying have been developed through ESA\u2019s 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\u2019s first precision formation flying mission.\u201d\u00a0<\/p>\n<\/p><\/div>\n The mysterious halo<\/b><\/p>\n The Sun’s fiery corona reaches temperatures above a million degrees Celsius, much hotter than the surface beneath it. This counterintuitive temperature difference has long been a topic in the scientific community.<\/p>\n Proba-3\u2019s ASPIICS is tackling this mystery by studying the corona very close to the Sun\u2019s surface. It can also see more detail, detecting fainter features than traditional coronagraphs thanks to a drastic reduction in how much \u2018stray\u2019 light reaches the detector.<\/p>\n Joe Zender, Proba-3 project scientist, adds: \u201cSeeing 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.\u201d<\/p>\n The Digital Absolute Radiometer (DARA) will measure the total solar irradiance \u2013 exactly how much energy the Sun is putting out at any one time. A third scientific instrument on Proba-3, the 3D Energetic Electron Spectrometer (3DEES), will detect electrons in Earth\u2019s radiation belts, measuring their direction of origin and energy levels.<\/p>\n<\/p><\/div>\n How to create a solar eclipse<\/b><\/p>\n \u201cI was absolutely thrilled to see the images, especially since we got them on the first try,\u201d comments Andrei Zhukov, Principal Investigator for ASPIICS at the\u00a0Royal Observatory of Belgium. \u201cNow we are working on extending the observation time to six hours in every orbit.\u201d\u00a0<\/p>\n The images were processed by the ASPIICS Science Operations Centre (SOC) hosted by the Royal Observatory of Belgium. Here, a dedicated team of scientists and engineers creates operational commands for the coronagraph based on requests from the scientific community and shares the resulting observations.<\/p>\n<\/p><\/div>\n Andrei explains: \u201cEach full image \u2013 covering the area from the occulted Sun all the way to the edge of the field of view \u2013 is actually constructed from three images. The difference between those is only the exposure time, which determines how long the coronagraph\u2019s aperture is exposed to light. Combining the three images gives us the full view of the corona.<\/p>\n \u201cOur \u2018artificial eclipse\u2019 images are comparable with those taken during a natural eclipse. The difference is 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. On top of that, natural total eclipses only last a few minutes, while Proba-3 can hold its artificial eclipse for up to 6 hours.\u201d<\/p>\n<\/p><\/div>\n Proba-3 mission manager Damien Galano notes: \u201cHaving 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.<\/p>\n \u201cAlthough 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\u2019s first images, which will no doubt be of high value to the scientific community.<\/p>\n \u201cThe formation flying we have achieved so far was performed autonomously, but under supervision of the ground control team, who were ready to intervene to correct any potential deviations. Our one remaining task is to achieve full autonomy, when our confidence in the system will be such that we will not even routinely monitor from the ground.\u201d<\/p>\n<\/p><\/div>\n New opportunities for \u2018digital eclipses\u2019<\/b><\/p>\n Proba-3\u2019s breathtaking images are also sparking a small revolution in the way computer models simulate the solar corona and create \u2018digital eclipses\u2019.\u00a0<\/p>\n Over the past years, several institutes around Europe have developed models to simulate these observations and give scientists the means to look at the Sun, but the source material needed to create these simulations is lacking.\u00a0\u00a0<\/p>\n \u201cCurrent coronagraphs are no match for Proba-3, which will observe the Sun\u2019s corona down almost to the edge of the solar surface. So far, this was only possible during natural solar eclipses,\u201d says Jorge Amaya, Space Weather Modelling Coordinator at ESA.<\/p>\n<\/p><\/div>\n \u201cThis huge flow of observations will help refine computer models further as we compare and adjust variables to match the real images. Together with the team at KU Leuven, which is behind one such model, we have been able to create a simulation of Proba-3\u2019s first observations.\u201d\u00a0<\/p>\n KU Leuven\u2019s \u2018COCONUT\u2019 software is one of multiple solar coronal models integrated within ESA’s Virtual Space Weather Modelling Centre (VSWMC). It can be combined with a vast array of computer models describing other physical processes connecting the Sun to Earth. All together, they help to offer a comprehensive image of the solar phenomena impacting our planet and help citizens and industry prepare against them.\u00a0<\/p>\n About Proba-3<\/b><\/p>\n The Proba-3 mission is led by ESA and put together by a consortium managed by Spain\u2019s\u00a0Sener, with participation of more than 29 companies from 14 countries and with key contributions from\u00a0GMV\u00a0and\u00a0Airbus Defence and Space\u00a0in Spain and\u00a0Redwire Space\u00a0and\u00a0Spacebel\u00a0in Belgium.\u00a0The mission was\u00a0launched on 5 December 2024\u00a0on a PSLV-XL launcher from Satish Dhawan Space Centre in Sriharikota, India.<\/p>\n \u00a0<\/p>\n Further information<\/b><\/p>\n For more information, see Proba-3’s first artificial solar eclipse,\u00a0Proba-3 Frequently Asked Questions and Proba-3 Media Kit.<\/p>\n<\/p><\/div>\n
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