Final images of the stricken Aeolus spacecraft

Final images of Aeolus during its brief phase as space debris captured by Fraunhofer FHR’s TIRA space-monitoring radar. (Note that the color represents the intensity of the radar echo, not the temperature.) Credit: Fraunhofer FHR

Aeolus remained in orbit around the Earth for four years, eleven months, and six days. For three hours on end, which is a very short period of time, there was space debris. This new animation was created from the last eight images ever taken of the European Space Agency’s Wind Characterization mission, which show it starting to falter as it was exposed to Earth’s atmosphere, during its very brief ‘trash’ phase.

International regulations on space debris mitigation set a limit for how long a satellite must remain in orbit once its mission is completed – and it should be no more than 25 years.

For low-altitude missions, their return is faster as they are caught in the Earth’s thin atmosphere and quickly returned home.

During Aeolus’ first-ever assisted reentry in July, not only was the (already low) debris fall risk reduced by a factor of 150, but the time Aeolus was left out of control in orbit was shortened by a few weeks. This reduces the risk of collisions with other satellites in this vital space route.

Infographic Falling to Earth takes a long time

In this chart from the European Space Agency and the United Nations Office for Outer Space Affairs (UNOOSA), find out how long it will take for satellites at different altitudes to return normally to Earth, and what needs to be done to dispose of them responsibly at the end of their lives. Credit: ESA/UNOOSA, CC BY-SA 3.0 IGO

animated moments

Aeolus became a wreck after executing the last command at 17:43 CEST on 28 July 2023, after which the flight control team could no longer talk to, listen to, or influence the satellite. After months of preparation and a week of intense and critical operations, the team did everything they could, and the satellite was deactivated – grounded – and “handed over” to the European Space Agency’s Space Debris Office, which tracked its final descent.

Looking at the ground trajectory (see map below), which is the trajectory on the ground that Aeolus would likely fly over, it was clear that the Tracking and Imaging Radar (TIRA) at Fraunhofer FHR in Germany would get a good view. Using a 34-meter antenna, TIRA tracked Aeolus at around 18:20 CET for about four minutes.

Map of the return of Aeolus

Aeolus returned to Antarctica again on July 28, 2023, at 20:40-42 CEST. By converting the normal, uncontrolled Aeolus re-entry into an auxiliary orbit, and choosing the best orbit for re-entry, the already very low risk of any remaining fragments landing near populated areas became 150 times less dangerous again. Credit: European Space Agency

Spacecraft observations and final return

“Spacecraft operators are used to dialogue with their missions, but debris cannot speak. These final observations prove that the final burn of Aeolus has gone well and that the ‘dead’ satellite is “It has reached the expected elliptical orbit, with an altitude of at least 120 kilometers.”

“If you think of Aeolus’ trajectory as a slightly compressed circle, rather than a line, that circle would get smaller and more circular as it returned, but its altitude would still go up and down. We used this orbit information to calculate a new estimate for the time of Aeolus’ return, which occurred just over Two hours and on the planned ground track.

This was the last time the mission teams saw Aeolus. It only took two hours before it fell into the Earth’s atmosphere above Antarctica, far from inhabited areas.

At about 20:40 CEST for about two minutes, Aeolus became a fireball – a temporary star in the atmosphere.

“Usually, once a mission gets into the nose of the rocket and closes the front around it, that’s the last time we ever expect to see it,” says Tommaso Parinello, Aeolus mission manager.

“With Aeolus, in a great example of sustainable spaceflight and responsible operations, we stayed with the mission for as long as we could, guiding its return as well as it was possible to do, and these images are our final farewells to a mission we’ve all missed, but whose legacy lives on.”

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