Homecoming: Aeolus could set an example of how to end space missions

5 Jul 2023

Aeolus in orbit. Image: ESA/ATG medialab

The ESA satellite to study the Earth’s wind profile is now on an unprecedented journey back home in a ‘unique’ ending attempt that could set new standards in space.

Last week, the European Space Agency (ESA) announced that Aeolus, its first satellite mission to study wind patterns on Earth, is set to begin its journey back home after five years of collecting data that has proved beneficial to our weather forecasting abilities.

Named after the Greek god of wind, Aeolus was launched into space in August 2018 to measure global wind speeds and directions to improve weather forecasts. It is the fifth satellite in the ESA’s Living Planet programme and was built by the defence and space division of Airbus.

“The countdown is truly on now for Aeolus as it begins its journey home. This week marks a significant milestone in the re-entry process. End-of-life tests have ended,” reads an ESA blogpost written by Josh Tapley last week.

The ESA confirmed in a tweet yesterday (4 July) that Aeolus’s descent has now been initiated. The satellite will naturally descend as Earth’s atmosphere and gravity combine to drag the satellite down from an altitude of 320km to 280km.

“How long this takes will depend on several factors, including solar activity, which has been ramping up in recent months,” Tapley went on.

“It was increasing doses of space weather, along with fuel finally running out after Aeolus long outlived its predicted lifetime, that meant we had to bring things to an end.

“It really has been like running against the wind.”

Responsibly ending space missions

What’s unique about the assisted decommissioning of the now retired wind tracking satellite is that it demonstrates to the growing commercial space industry it is possible to responsibly end space missions without adding to the already high amount of space debris in orbit.

One ESA report last year estimated that more than 30,000 pieces of space debris have been spotted and are being regularly tracked by space surveillance networks. For context, there were 10,000 catalogued debris objects surrounding Earth at the end of 2003.

According to NASA, space debris is mostly human-generated objects. It includes pieces of spacecrafts and flecks of paint, parts of rockets, satellites that have stopped working and fragments resulting from explosions in orbit, posing a serious threat to active spacecrafts.

In fact, Aeolus came close to collision with a SpaceX satellite in 2019 when the Elon Musk-founded company said it would not move Starlink 44 despite it being in a possible collision course with the ESA satellite. This resulted in Aeolus having to be manoeuvred out of the way to avoid collision.

Klaus Merz of ESA’s space debris office said at the time the incident highlighted the need to improve coordination among satellite operators as Earth’s orbit becomes increasingly crowded despite an absence of traffic rules.

While satellites have to dodge each other from time to time, “it is really the first time that we had to do it with one of these big (satellite) constellations,” Merz said at the time.

So, Aeolus’s journey back home is not only a welcome move by the ESA, but also a precedent to set standards of best practice as space gets more crowded with debris. But, as with any pioneering attempt, there is every chance Aeolus’s return may fail.

“This is a first of its kind attempt that might not work. In the case we need to abort, Aeolus will continue its uncontrolled descent as originally planned,” cautioned Tapley.

“In the meantime, over the coming weeks, we’ll reveal more about the hard work and complex science that goes into planning and attempting a unique end for a pioneering mission.”

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Vish Gain is a journalist with Silicon Republic