Aeolus orbited Earth for nearly five years, delivering unprecedented global wind direction data. However, in the middle of this summer, it was time to eliminate the satellite – its safe operation time was over. The European Space Agency (ESA) used the situation to test a new maneuvering procedure for the first time, guiding satellites towards a fiery demise in the Earth’s atmosphere.
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The “Aeolus” satellite was equipped with modern laser technology and was able to observe wind flows on a global scale. The data collected over nearly five years helped improve the accuracy of both climate models and daily weather forecasts.
Most satellites in low Earth orbit burn up in the atmosphere at the end of their service life. In the case of larger machines, some debris may also reach the ground. The difference is how controlled it is and how precisely the place where the satellite debris could land can be determined. In the worst case, no final maneuver is performed to decelerate the satellite and enter the atmosphere at the desired location. This poses greater risks to other satellites in orbit, its people and infrastructure on Earth. Usually, this braking, corrective maneuver is performed so that at least approximately you can know where the unburnt debris will land in the atmosphere. The further from populated areas, the better.
Foto: University of Bath/C. Wright
“Aeolus” made it possible for the first time to map changes in wind flows in such detail on a global scale.
ESA went a step further with the elimination of “Aeolus” by testing assisted insertion into orbit. Unlike the times when a satellite is slowed down once, then hoping that the calculations were accurate and that its trajectory will descend exactly as predicted, the ESA lowered the altitude of this artificial satellite in several passes. Gradually, it orbited our planet lower and lower, but still remained in orbit. This allowed the satellite to be easily tracked from Earth and much more precisely determined where it would begin its fall through the atmosphere. For now, the risk of a “space debris” hitting a populated area and injuring or killing people is small. EKA explains that such an assisted introduction of a satellite into the atmosphere reduces the already small risk by another 150 times.
In addition, by maintaining limited control over the satellite and monitoring its maneuvers until the last moment, safety in orbit, where the number of artificial satellites is increasing, is significantly improved. For comparison, if in 2010 there were about a thousand working satellites orbiting the Earth, then there are more than six thousand. The number is growing rapidly due to projects such as Starlink. Each low-Earth orbit collision between two satellites will create a huge amount of new debris, increasing the risks of collisions in the future. In a worst-case scenario, a chain reaction known as Kessler syndrome can begin. If ten or more years ago this seemed like only a theoretical fear, now, with the number of satellites growing rapidly, it is a very real threat.
The last moments of the “Aeolus” satellite in orbit were captured by the 34-meter diameter antenna of TIRA (“Tracking and Imaging Radar”) located in Germany. The antenna tracked the position of the satellite for about four minutes. The ESA has just published an animation of how the radar “saw” the satellite shortly before it entered the atmosphere. In this image, the brighter colored areas represent the strength of the reflected signal, not the surface temperature of the satellite, as the red-orange gamut of the image might misleadingly suggest.
Photo: Fraunhofer FHR
“Aeolus” entered the atmosphere at a speed of 26.9 thousand kilometers per hour or about 7.5 kilometers per second. According to ESA calculations, 80% of the mass of the satellite burned up in the air, while 20% of the debris reached the ground. They fell far from inhabited places in Antarctica.
The liquidation of “Aeolus” is cited by ESA as an example of sustainable management in space – devices that have completed their function must be safely removed from orbit in order not to hinder space flights in the future. There are still countries, such as China, whose practices in this area are not the most responsible. There have been cases of Chinese satellites or launch vehicle parts entering the Earth’s atmosphere out of control, endangering people and infrastructure.
2023-09-11 12:24:17
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