Scientists Chase Falling Satellite to Study Atmospheric Pollution from Spacecraft Reentries

Scientists take advantage of the spectacular airborne chase of a falling satellite to gather rare data on atmospheric pollution from burnt-up spacecraft. In September 2024, a group of European researchers hopped on an aeroplane outfitted with 26 cameras and flew into the night sky to watch the satellite Cluster Salsa make its flaming return to Earth over the Pacific Ocean. The mission, which was launched from Easter Island, sought chemical byproducts that would have been released during that short, meteor-like reentry event. Despite the glare of bright natural light that impeded a clear view, the researchers captured for the first time images of the satellite fracturing and chemicals being released as it fell to Earth.

Satellite Reentries May Impact Ozone and Climate, Scientists Warn

As per the report presented at the European Conference on Space Debris, reentry produced lithium, potassium, and aluminum emissions — elements with the potential to impact the ozone layer and Earth's climate. Stefan Löhle of the University of Stuttgart mentioned that the satellite's weak trail indicated that pieces splintered off and burned with less ferocity than predicted. The satellite started to disintegrate at about 80 kilometres above sea level, and the observations stopped at a height of around 40 kilometres due to the visual extinction.

Such events are increasingly important to monitor as satellite reentries grow in frequency. Although spacecraft such as those in SpaceX's Starlink fleet are made to burn up completely, surviving debris and dust particles could still affect the upper atmosphere, scientists caution. The aluminum oxide from the melting satellites, for example, could be involved in long-term atmospheric effects, such as changes in thermal balance and ozone destruction.

This mission marks only the fifth time a spacecraft reentry has been observed from the air. Researchers hope to align their collected data with computer models to estimate how much mass satellites lose during disintegration and how that mass interacts chemically with the atmosphere. The data also suggest that some titanium components from the 550-kilogram Cluster Salsa may have survived reentry and landed in the Pacific Ocean.

As more satellites return to Earth, researchers plan to repeat the chase with Salsa's sister satellites—Rumba, Tango, and Samba—expected to re-enter by 2026. Despite daytime limitations affecting some measurement techniques, these missions may help clarify how spacecraft pollution influences Earth's upper atmosphere and climate.