Final preparations have begun for a landmark space mission that will use satellites flying in close formation to create artificial solar eclipses high above Earth.
The Proba-3 mission is the European Space Agency’s first attempt at precise formation flying in orbit and calls for two spacecraft to loop around the planet in an arrangement that never deviates by more than a millimeter. about the thickness of a human fingernail.
If all goes well, the spacecraft will blast off from India’s Satish Dhawan Space Center in Sriharikota, on the Bay of Bengal coast, at 16:08 local time (10:38 UK time) on Wednesday. After a four-month journey, the probes will reach a highly elliptical orbit that comes as close as 370 miles to Earth before swinging out for more than 37,000 miles.
“This is an experiment in space to demonstrate a new concept, a new technology,” said Damien Galano, the Proba project manager at ESA. “It is very challenging because we have to control the flight path of the two spacecraft very well.”
If the satellites work as intended, they will be so aligned with the sun that the lead spacecraft casts a carefully controlled shadow on its partner, allowing instruments on the latter to measure the sun’s corona, the outermost layer of its atmosphere.
Traditionally, scientists have studied the Sun’s ring-like corona during solar eclipses, when the Moon blocks enough of the Sun’s glare to make the corona visible from Earth. The job requires scientists to chase eclipses around the world, often for only minutes of viewing time, or none at all if the view is obscured by cloud.
The €200 million (£166 million) Proba-3 mission promises to change scientists’ understanding of the corona by producing 50 artificial solar eclipses a year, each lasting six hours. The lead spacecraft carries a 1.4-meter-wide occulter disk to block the sun as seen from the second spacecraft, which turns the pair into a 150-meter-long instrument called a coronagraph.
Data from the mission should shed light on the long-standing mystery of why the corona is so much hotter than the sun itself; the sun’s surface is about 5500C, but the corona can exceed 1mC.
By better understanding the corona, scientists hope to improve their predictions of solar weather, coronal mass ejections – where pulses of plasma and magnetic field burst into space – and solar storms, which can damage spacecraft and cause power outages and communication disruptions on Earth. to improve.
The Proba-3 spacecraft will orbit the planet once every 19.7 hours for two years. For six hours in each orbit, the satellites will fly in formation, with optical sensors and flashing LEDs to track each other, and a precision laser system to automatically fine-tune their distance and orientation. The first images from the mission are expected as soon as March 2025.
Beyond the main objectives of the mission, ESA scientists set aside time to test maneuvers that could be useful in the future to service faulty satellites or remove “non-cooperative” hardware and debris from orbit.
Formation flying could usher in a new era of space-based observatories and instruments by allowing multiple spacecraft to work together in precise configurations. “If we could have several satellites close together in an absolute, accurate, precise formation, we could assemble larger instruments composed of several satellites,” said Dietmar Pilz, the director of technology at ESA. . These multi-satellite instruments can be used to study the climate crisis, objects in the solar system and more distant planets around distant stars.
“We all know that the launchers have increased in their power and the masses they can bring into space,” Pilz said, referring to the heavy loads carried by modern rockets. “But no matter what you do, there’s always a limit.”
