Right on track: Aeolus reentry map

Right on track: Aeolus reentry map
by Staff Writers
Paris (ESA) Aug 04, 2023

Pinpointing the exact location where Aeolus reentered our atmosphere is not easy, as no one was there to witness it. "and that's exactly what we wanted," explains Mission Manager Tommaso Parrinello.

"The goal of this first-of-its-kind assisted reentry was to guide Aeolus on a safe final path, where it would disintegrate in Earth's atmosphere as far as possible from inhabited regions."

Aeolus reentered over Antarctica on 28 July 2023 at 20:40-42 CEST. By turning Aeolus's natural, uncontrolled reentry into an assisted one, and choosing the best reentry orbit, the already very small risk from any surviving fragments landing near populated areas was made a further 150 times less risky.

In a thorough assessment from ESA's Space Debris Office, based on USSPACECOM and ESA's own data acquired during Aeolus's last orbits, this map has been produced showing the assessed location of Aeolus's disintegration in the atmosphere and where any surviving fragments may have fallen.

Various tracks were technically possible, but an orbit guiding Aeolus towards a long path over the Atlantic was the final choice, as it saw Aeolus descend as far away from inhabited regions as possible during its final Earth orbit.

The risk of a piece of debris falling on your head is three times lower than a meteorite doing the same. It's extremely, extremely, unlikely - and to date, unheard of. Nevertheless, ESA takes the risk seriously. A first assessment showed teams could lower the risk a further 42 times, but after different 'ground tracks' were analysed teams found they could do even better, finally aiming for a path that lowered the risk by 150.

At around 18:40 (20:40 CEST) and for about two minutes, Aeolus became a fireball - a temporary shooting star in the atmosphere. At around 18:46 UTC (20:46 CEST), a second location is marked where any surviving fragments may have reached the ground.

This final position is very close to the intended final location. In other words, despite travelling at approximately 7.5 km per second and not being designed to be flown at such low altitudes, the series of manoeuvres performed by ESA's mission control, designed by ESA's flight dynamics experts and overseen by the Agency's Space Debris Office, got Aeolus just minutes away from where they had intended.

Aeolus's final moments are not an ideal to be replicated for new missions. But for those already in orbit, launched before current debris mitigation guidelines came into place, it demonstrates what is possible when space actors go 'above and beyond'. It may not be replicable for every mission already in orbit, but shows that it is possible, and important, to try to do even more than the rules say we must.

"Space is limited and shared, and therefore space sustainability must be a global effort," explains Holger Krag, Head of ESA's Space Safety Programme.

"To ensure spaceflight for the future, we need to significantly improve the way we design and operate missions today. With Aeolus, we decided to go well beyond what Aeolus was required to do. We hope that by acting as a role model, we can encourage other actors in space to similarly ensure their missions are flown sustainably."