Twin spacecraft Proba-3 launched on unique mission to create artificial solar eclipses
Two European satellites were launched from India’s Satish Dhawan Space Center on December 5, 2024, as part of ESA’s Proba-3 mission, marking a new chapter in solar corona research.
Artist's view of Proba-3 on an ISRO PSLV-XL launch vehicle. Image credit: ESA/P. Carril
- Proba-3, launched on December 5, is the world’s first precision formation flying mission designed to create artificial solar eclipses in space.
- The mission offers up to 6 hours of continuous observation of the Sun’s corona per orbit.
- The dual-satellite mission maintains a 1 mm (0.039 inches) accuracy at a 144 m (472 feet) separation, enabling solar imaging capabilities.
- By bridging observational gaps, Proba-3 aims to unravel mysteries of the Sun’s corona, solar winds, and coronal mass ejections, while also laying the foundation for future multi-satellite collaborations.
Proba-3, short for ‘Project for On-Board Autonomy 3’, is a mission by the European Space Agency (ESA) designed to create artificial solar eclipses when needed.
The mission uses two spacecraft, Occulter, and Coronagraph, that fly in a highly precise formation to study the Sun’s outer atmosphere. The project is aimed to improve solar research and develop new tools for space-based science.
“Proba-3 has been many years in the making, supported through ESA’s General Support Technology Programme fostering novel technologies for space. It is an exciting feeling to see this challenging enterprise enter orbit,” Dietmar Pilz, ESA Director of Technology, Engineering and Quality noted.
The operational phase of Proba-3 will start in early 2025. Once separated, the satellites will begin generating artificial eclipses twice a week, each lasting up to 6 hours, delivering over 1 000 hours of observation during the 2-year mission.
Initial scientific images are expected by March 2025, following rigorous system checks.
About the mission
Proba-3 was launched on the Polar Satellite Launch Vehicle – C59 (PSLV-C59) of the Indian Space Research Organisation (ISRO) from the First Launch Pad (FLP), Satish Dhawan Space Centre (SDSC-SHAR), Sriharikota, India. The 2 satellites, together weighing 1 210 kg (2 668 pounds), were placed into a highly elliptical orbit.
“We are honoured that ESA entrusted NewSpace India Limited, NSIL, with its Proba-3 mission, and we are extremely satisfied to have delivered the satellites precisely into their designated orbit,” Radhakrishnan Durairaj, Chairman and Managing Director of NSIL said.
“This is an extremely ambitious mission, with an ambitious orbit to go with it: the satellites have been placed into a highly elliptical orbit which extends more than 60 500 km [37 600 miles] from the surface of Earth. Reaching this orbit required the most powerful PSLV-XL variant of our launcher, equipped with additional propellant in its six solid rocket boosters.
This In-Orbit Demonstration (IOD) mission is 4th in the series and costs about €200 million ($211 million). It involves 14 ESA member countries and Canada.
The satellites will remain connected during the initial setup phase before separating to start working together.
The mission, Proba-3, requires very high precision, keeping a distance of about 144 m (472 feet) between the spacecraft with an accuracy of 1 mm (0.039 inches), roughly the thickness of a fingernail, as they orbit Earth.
“Today’s liftoff has been something all of us in ESA’s Proba-3 team and our industrial and scientific partners have been looking forward to for a long time. I’m grateful to ISRO for this picture-perfect ascent to orbit. Now the hard work really begins, because to achieve Proba-3’s mission goals, the two satellites need to achieve positioning accuracy down to the thickness of the average fingernail while positioned one and a half football pitches apart,” Damien Galano, Proba-3 mission manager, said.
How does space technology power artificial solar eclipses?
Natural solar eclipses provide short and rare chances to study the Sun’s corona, where plasma is heated to over 1 million °C (1.8 million °F). This part of the Sun is still not well understood. Proba-3’s artificial eclipses, lasting up to 6 hours per orbit, offer much more time for observation.
“Despite its faintness, the solar corona is an important element of our Solar System, larger in expanse than the Sun itself, and the source of space weather and the solar wind,” Andrei Zhukov, Principal Investigator for Proba-3’s ASPIICS coronagraph said.
The mission’s primary instrument, the Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun (ASPIICS), is designed to capture detailed images of the Sun’s inner corona. It aims to close the gap in observations between the Sun’s surface and its outer layers.
Technical precisions
The Occulter satellite carries a 1.4 m (4.6 feet) disc to block sunlight for the Coronagraph spacecraft, creating an artificial eclipse. This setup helps avoid the problems with light distortion seen in traditional coronagraphs, allowing for clearer images.
“There was simply no other way of reaching the optical performance Proba-3 requires than by having its occulting disc fly on a separate, carefully controlled spacecraft. Any closer and unwanted stray light would spill over the edges of the disc, limiting our close-up views of the Sun’s surrounding corona,” Joe Zender, ESA’s Proba-3 mission scientist explained.
The satellites stay in position using advanced GPS, star trackers, lasers, and radio links, all while flying on their own. This precise flying could lead the way for future space missions, like building virtual telescopes or setting up multi-satellite observatories.
Scientific relevance
- Investigating corona heating
The Sun’s surface, or photosphere, reaches temperatures of 5 500 to 6 000 °C (9 932 to 10 832 °F), while its corona heats up to millions of degrees. This phenomenon remains a mystery.
By imaging the inner corona down to 70 000 km (43 500 miles) above the Sun’s surface, Proba-3 is aimed to identify mechanisms, such as plasma waves, responsible for this dramatic temperature disparity.
- Studying solar winds
Solar winds are streams of charged particles released by the Sun with varying speed and intensity.
The mission will trace the origins of these winds, focusing on their acceleration within coronal holes and magnetic loops.
- Understanding Coronal Mass Ejections (CMEs)
CMEs, massive eruptions of plasma and magnetic fields, can trigger geomagnetic storms that disrupt Earth’s power grids, satellites, and communication systems.
The extended observation periods of Proba-3 will provide important data on the formation and evolution of CMEs.
Legacy of Proba missions
Proba-3 continues the European Space Agency’s tradition of innovation established by its Proba series.
Proba-V, launched in 2012, contributed to tracking Earth’s vegetation. Proba-2, introduced in 2009, was dedicated to studying the Sun and monitoring space weather.
Proba-1, launched in 2001, focused on Earth observation using hyperspectral imaging.
The mission, Proba-3, tackles long-standing questions about solar phenomena and shows that precise formation flying is possible. It opens the door for future large-scale space projects, such as climate observation and asteroid exploration.
“It is not practical today to fly a single 150 m [500 feet] long spacecraft in orbit, but if Proba-3 can indeed achieve an equivalent performance using two small spacecraft, the mission will open up new ways of working in space for the future. Imagine multiple small platforms working together as one to form far-seeing virtual telescopes or arrays,” Josef Aschbacher, ESA Director General, remarked.
References:
1 PSLV-C59/Proba-3 Mission – ISRO – December 2, 2024
2 Eclipse-making double satellite Proba-3 enters orbit – ESA – December 5, 2024
3 Five space mysteries Proba-3 will help solve – ESA – December 3, 2024
4 Proba-3 Media Kit – ESA – December 6, 2024
5 Proba-3 – ESA – December 6, 2024
Rishika holds a Master’s in International Studies from Stella Maris College, Chennai, India, where she earned a gold medal, and an MCA from the University of Mysore, Karnataka, India. Previously, she served as a Research Assistant at the National Institute of Advanced Studies, Indian Institute of Science, Bengaluru, India. During her tenure, she contributed as a Junior Writer for Europe Monitor on the Global Politics website and as an Assistant Editor for The World This Week. Her work has also been published in The Hindu newspaper, showing her expertise in global affairs. Rishika is also a recipient of the Women Empowerment Award at the district level in Haryana, India, in 2022.
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