Aeolus Wind Mission: ESA Successfully Carries Out Assisted Reentry

Sunday - July 30 2023, 20:15 UTC - 1 year ago

The European Space Agency's successful wind mission Aeolus reentered Earth's atmosphere safely on Sunday, July 28, with the help of ESA's mission control team. Prior to Aeolus, wind measurement was done from aircrafts and balloons. This is part of ESA's wider Zero Debris approach to ensure safe and environmentally responsible operations in Earth's orbit.

Surpassing scientific expectations and exceeding its planned life in orbit, the Aeolus wind mission has been hailed as one of the European Space Agency’s most successful Earth observation missions. And now, its end will go down in history too, thanks to the ingenuity of ESA’s mission control team who guided this remarkable satellite down to Earth’s atmosphere for a safe reentry.

Aeolus – ESA’s wind mission – reentered Earth’s atmosphere on July 28 at around 21:00 CEST above Antarctica, confirmed by US Space Command.

The reentry comes after a series of complex maneuvers that lowered Aeolus’ orbit from an altitude of 320 km to just 120 km to reenter the atmosphere and burn up.

Crucially, these maneuvers – the first assisted reentry of its kind – positioned Aeolus so that any pieces that may not have burned up in the atmosphere would fall within the satellite’s planned Atlantic ground tracks.

Today, satellite missions are designed according to regulations that require them to minimize the risk of causing damage on their return to Earth. This would typically be achieved by the majority of the satellite burning up on reentry or through a controlled reentry at the end of their lives in orbit.

However, when Aeolus was designed back in the late 1990s no such regulations were in place.

So, after running out of fuel and without intervention, Aeolus would have reentered Earth’s atmosphere naturally within a few weeks from now – but with no control over where this would happen.

Satellites and rocket parts fall back to Earth roughly once a week, and pieces that survive have only very rarely caused any damage, so the risk of Aeolus causing harm was always incredibly small. In fact, the chance of being struck by a piece of debris is three times less than being struck by a meteorite.

Nevertheless, ESA went above and beyond for Aeolus and attempted a new way of assisting its reentry to make it even safer.

Essentially trying to make a satellite do what it was never designed to do involved a huge amount of thinking and a lot of planning.

Then, over the last week, the team of spacecraft engineers, flight dynamics experts, and space debris specialists at ESA’s ESOC mission control center in Germany set to work. They used the satellite’s remaining fuel to carry out a series of burns to lower Aeolus and place it into the best position to reenter.

And they pulled it off – with Aeolus reentering in line with current regulations.

ESA’s Director of Operations, Rolf Densing, said, "The teams have achieved something remarkable. These maneuvers were complex, and Aeolus was not designed to perform them, and there was always a possibility that this first attempt at an assisted reentry might not work."The Aeolus reentry was always going to be very low risk, but we wanted to push the boundaries and reduce the risk further, demonstrating our commitment to ESA’s Zero Debris approach.

"We have learned a great deal from this success and can potentially apply the same approach for some other satellites at the end of their lives, launched before the current disposal measures were in place." .

This assisted reentry is just one part of ESA’s wider Zero Debris approach to ensure safe and environmentally responsible operations in Earth’s orbit.