The European Space Agency (ESA) launched the Aeolus satellite in 2018 and since then it has spent five years measuring the terrestrial winds, but on July 28, at 9:00 p.m., it burned up in the Earth's atmosphere, just above the antartida. It was not due to a satellite accident. It was the inauguration of a new era at ESA.
Today European missions are designed to burn up in the atmosphere to fulfill ESA's commitment not to generate space debris. But there is always the risk that some fragments fall into inhabited areas above which intervention from Earth is necessary, to achieve controlled entry. Furthermore, in the case of Aeolus, it could not be made to fall at Point Nemo, the graveyard of space junk located in the Pacific about 2,700 km from the nearest land mass, because its orbit was polar.
To further complicate matters, Aeolus predated this standard, so it was not designed, nor did it have the technology or means for a fully controlled re-entry into the atmosphere, in which the unburned fragments fell at a particular, pre-chosen spot. .
In this case, if those pieces did not burn in the reentry, they would have fallen in Antarctica.
The risk of damage was incredibly small anyway. "The probability of a piece of the satellite falling on top of a person was 65,000 times less than a lightning strike," Spanish Isabel Rojo, director of Aeolus flight operations, explained to Efe, who for a week commanded a team of more than 50 engineers and scientists that he brought back to the satellite.
Still, the agency calculated the optimal orbit to further reduce that minimal risk; the goal was to reduce it by 42 times compared to a natural reentry.
ESA has opted for the "zero waste" policy in space and Aeolus paves the way to re-enter other missions. Assisted reentry could be done with satellites that have a propulsion system and fly in low orbit.
“Aeolus has shown that it can be done and sends the message that if you think, calculate and execute well, even with a lot of effort, it is possible”.
But, of course, "it always happens that in this field, reality and theory are two things that are close but are not identical," adds Rojo. The engineers did it in two 12-hour shifts from the ESA headquarters control center in Darmstadt, Germany, and other locations, thanks to a sequence of maneuvers.
They began on July 24, when the satellite, which had begun to lose altitude since June 19, was about 280 kilometers from Earth. That day, says Rojo, they already started "with a small deviation" from the initial scenario. The idea was to do a maneuver to lower the satellite to an altitude of 250 kilometers, but two had to be done.
This was not the only unforeseen event. When the spacecraft turned to start operations, the GPS was reconfigured, with which the flight dynamics equipment, which calculates the orbits and the parameters of the maneuvers, ran out of data for a while.
Thursday's day, in which the ship had to be lowered from 250 km to 150 km, began as planned, but hours later another problem arose: the reconfiguration of the electronics that controls, among other things, the propulsion system. The maneuvers ended on Friday with the descent of Aeolus to 120 kilometers from Earth. Hours later the re-entry ended. The satellites begin to burn at about 80 km.
