Satellite becomes first to be guided back into Earth's atmosphere, reducing debris risk

A trailblazing satellite has returned to Earth after a complicated assisted crash that marked the first of its kind in history, the European Space Agency announced last week. 

The satellite, named Aeolus like the ruler of winds in Greek mythology, initially launched in 2018 to observe the planet's weather patterns and conduct climate research on a global scale. Aeolus' mission was novel in and of itself, since that had never been done before, and the satellite was praised throughout its time in orbit for the ways in which it improved weather forecasting. 

Aeolus continued to observe Earth from space for the better part of 4 1/2 years —around 18 months longer than its anticipated lifespan— before beginning its descent back toward the atmosphere earlier this summer. With an intended crash site set in the Atlantic Ocean, officials said risks that falling debris could harm people or property were minimal as the satellite burned up on its way down. 

But, to demonstrate what the European Space Agency said is its "wider commitment to to the long-term safety and sustainability of space activities," the agency used the defunct orbiter's dwindling fuel supply to successfully carry out an "assisted reentry" in an effort to reduce the likelihood of lost debris altogether. The assist, a world first, meant control teams on the ground were tasked with guiding Aeolus through part of its descent, from an altitude of 320 kilometers to 120 kilometers, before it entered Earth's atmosphere and burned up. 

It aimed to position the satellite in such a way "so that any pieces that may not have burned up in the atmosphere would fall within the satellite's planned Atlantic ground tracks," the ESA said in a news release shared to its website on Saturday. One day earlier, the agency announced on Twitter —now X— that Aeolus had reentered the atmosphere above Antarctica.

"The Aeolus mission control team in Germany is now wrapping up after a long week of complex operations," the agency wrote in a separate message shared Friday evening. "They have done everything they planned in what is a first-of-its-kind assisted re-entry. Aeolus –a mission that revolutionised wind profiling— is now out of their hands."

Rolf Densing, the director of operations at ESA, described the assisted reentry as "remarkable" and noted that the satellite was not designed to be compatible with those kinds of maneuvers in a statement released by the agency.

"These manoeuvres 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 statement read. "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."

Today, space agencies are required to comply with regulations when building spacecrafts that will allow them to perform "control reentries" that aim to minimize any damages to Earth from falling debris. But those regulations were not in place yet when Aeolus was designed in the 1990s, according to the ESA. Densing noted that the assisted entry performed on Aeolus could potentially provide a blueprint for other satellites of similar age.

"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," he said in the statement. The ESA has pledged that all of its missions will be "debris neutral" by 2030. 

Between 200 and 400 tracked objects —called space debris— enter Earth's atmosphere every year, the National Environmental Satellite, Data, and Information Service reported in 2018. Space debris refers to defunct man-made objects, like satellites and used rocket stages, as well as other fragments "from disintegration, erosion, and collisions," the service said.

In:
• Weather Forecast
• European Space Agency