PROBA-3 (Project for On-Board Autonomy-3) is an innovative initiative spearheaded by the European Space Agency (ESA) aimed at revolutionising space observation through advanced formation flying technology. Scheduled for launch in November 2024, this mission exemplifies a significant international collaboration, bringing together expertise and cutting-edge technologies from multiple European countries and the Indian Space Research Organisation (ISRO). The PROBA-3 mission has passed its final test and is now ready to be sent to India, where it will be launched by the ISRO. PROBA-3 will be transported to the Satish Dhawan Space Centre later this month and the mission will be launched using ISRO’s trusted PSLV-XL rocket.
What is the PROBA-3 mission?
PROBA-3 is the ESA’s first mission dedicated to precision formation flying. “In this mission, two satellites will operate together in a coordinated manner, maintaining a set distance and alignment in space as if they were part of a single, large structure. The goal is to test, and demonstrate, advanced technologies for formation flying and conduct experiments related to spacecraft rendezvous the meeting, or docking, of two spacecraft,” said space expert Girish Linganna.
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The mission will showcase formation flying as part of a major scientific experiment. The two satellites will work together as a single unit to carry out the experiment, demonstrating how closely coordinated satellite systems can function in space. Both the satellites will combine to create a 144-metre-long solar coronagraph, a special tool designed to study the Sun’s faint outer atmosphere, or the corona. A solar coronagraph works by blocking out the bright light from the Sun’s surface, creating an artificial eclipse.
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“The faint corona is usually hidden by the Sun’s intense brightness, but this setup will allow scientists to observe, and analyse, the corona much closer to the Sun’s surface than ever before, providing new insights into solar activity. The coronagraph helps in studying solar activity, such as solar flares and coronal mass ejections which can affect space weather without waiting for an eclipse,” added Linganna.
The core objective of PROBA-3 is to create an artificial eclipse by precisely coordinating two independent satellites. This capability will enable scientists to observe the Sun's corona, a region typically obscured by the intense brightness of the Sun. By blocking out sunlight, the satellites will facilitate unprecedented studies of solar phenomena, including solar flares and coronal mass ejections. Understanding these phenomena is crucial, as they can have significant effects on space weather, which in turn impacts satellite communications, navigation systems, and power grids on Earth.
“In addition to demonstrating high-precision formation flying, PROBA-3 is set to validate new technologies essential for maintaining the satellites in close proximity. The mission aims to reach Technology Readiness Level 9 (TRL 9), showcasing advancements in metrology systems, control logic, and manoeuvring capabilities. This will allow for precise manoeuvres necessary for the mission's success and for future space exploration endeavours,” explained Srimathy Kesan, founder and CEO of Space Kidz India, which is into design, fabrication and launch of small satellites, spacecraft and ground systems.
How is PROBA-3 different from other solar observation projects?
A key aspect that sets PROBA-3 apart from traditional solar observation projects is its innovative approach to utilising smaller, agile satellites equipped with advanced sensors. Many conventional solar missions involve large, complex spacecraft, which can be expensive and challenging to manoeuvre. In contrast, PROBA-3's use of two smaller satellites operating in a highly coordinated formation demonstrates that complex observational tasks can be accomplished efficiently and cost-effectively without the need for oversized equipment. This flexibility paves the way for more versatile missions, allowing space agencies to maximise their scientific output while operating within constrained budgets.
The collaborative nature of the PROBA-3 mission further enhances its significance. It involves contributions from various ESA member states, including France, Belgium, and the Netherlands, alongside ISRO. This international partnership not only facilitates the sharing of technological expertise but also fosters a collaborative spirit in addressing common challenges in space exploration. Such partnerships are increasingly important as space missions become more ambitious and complex, requiring a diverse range of skills and knowledge.
As the launch date approaches, extensive testing and simulations are being conducted to ensure the mission's success. The excitement surrounding PROBA-3 reflects the scientific community's anticipation of potential breakthroughs, particularly in solar physics and its implications for understanding space weather. The data collected during this mission could transform our understanding of solar activity, leading to improved forecasting models for space weather events. This is especially crucial for mitigating risks to both civilian and military satellite operations and for protecting critical infrastructure on Earth from the effects of solar storms.
“By creating an artificial eclipse, this mission promises to enhance our understanding of the Sun's behaviour and its broader impacts on the solar system. This mission not only advances our knowledge of the cosmos but also sets a precedent for future collaborations in space exploration, paving the way for a new generation of scientists and explorers dedicated to unraveling the mysteries of our universe,” said Kesan.
As part of the mission the occulter spacecraft is a satellite designed to block, or ‘occlude’, the Sun’s bright light so that other instruments, such as the coronagraph, can get a clearer view of the Sun’s outer atmosphere (the corona). By positioning itself in front of the Sun, it creates an artificial eclipse, making it easier to study the faint details of the corona without interference from the Sun’s intense brightness.
Both the coronagraph spacecraft (weighing 340-kg) and the occulter spacecraft (weighing 200kg) will operate in a high Earth orbit, taking 19.7 hours to complete one orbit. At its highest point, the orbit will reach 60,530km and, at its closest point, it will be 600km above Earth. The primary instrument on board is an external coronagraph. The mission’s communication will be supported by an antenna located at Santa Maria in the Azores, with a ground station in Redu, Belgium.
