The European Space Agency (ESA) is gearing up for a groundbreaking mission, Proba-3, set to launch on December 4 from the Satish Dhawan Space Centre in India. This revolutionary project, in collaboration with the Indian Space Research Organisation (ISRO), aims to artificially create solar eclipses using two satellites flying in precise formation. This mission is poised to transform solar research and advance spaceflight technologies.
Bold Experiment in Formation Flying
Proba-3 marks ESA’s first venture into precision formation flying in orbit, a feat requiring unprecedented accuracy. The mission involves two spacecraft—the Occulter Satellite (OSC) and the Coronagraph Satellite (CSC)—orbiting Earth at a fixed distance of 150 meters, with their alignment deviating by no more than a millimeter. This challenging operation uses advanced sensors, flashing LEDs, and lasers to control their positioning.
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The OSC carries a 1.4-meter-wide occulting disc designed to block sunlight, casting a controlled shadow onto the CSC. Positioned within this shadow, the CSC is equipped with a telescope to study the Sun’s corona—the outermost layer of its atmosphere.
Why Study the Corona?
The solar corona holds critical clues about solar dynamics and space weather phenomena such as solar storms and coronal mass ejections (CMEs), which can disrupt power grids, satellite operations, and communications on Earth. However, observing the corona is notoriously difficult, as its light is a million times dimmer than direct sunlight. Traditional studies rely on rare natural eclipses or ground-based instruments often hindered by weather conditions.
Proba-3 addresses these challenges by creating up to 50 artificial eclipses annually, each lasting six hours, providing an unprecedented opportunity for continuous observation. Scientists hope the mission will unravel the mystery of why the corona’s temperature—over 1 million °C—far exceeds the Sun’s surface temperature of about 5,500 °C.
Cutting-Edge Orbit Design
The mission’s satellites will orbit Earth every 19.7 hours, with their paths taking them as close as 370 miles (600 km) to Earth and as far as 37,000 miles (60,000 km). Operating at higher altitudes during certain phases minimizes gravitational forces, conserving fuel and extending the mission’s two-year lifespan. The first images are expected by March 2025.
Revolutionizing Spaceflight
Beyond its scientific goals, Proba-3 is a technological testbed. Its success could pave the way for future missions involving multi-satellite configurations. Formation flying could enable the assembly of larger instruments in space, such as advanced observatories for studying exoplanets, the solar system, or even Earth’s climate.
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The mission also includes experiments to refine techniques for satellite servicing and space debris removal. These capabilities are critical as space traffic and debris continue to grow, posing challenges to sustainable space exploration.