First database of pollutant and CO2 emissions from satellite megaconstellations

Satellite megaconstellations such as SpaceX’s Starlink and Eutelsat’s OneWeb each contain hundreds to thousands of satellites and are already three-quarters of all satellites in low-Earth orbit after only four years of megaconstellation launches.

These megaconstellations are contributing to rapid increases in rocket launches and the amount of mass re-entering the Earth’s atmosphere, leading to the release of harmful air pollutants and carbon dioxide throughout all atmospheric layers from the surface of the Earth up to hundreds of kilometres overhead.

Research Fellow Dr Connor Barker, who led the study, explains that this is troubling because “megaconstellations' emissions are small compared to surface-based emissions like cars or agriculture, however, we know that they have an outsized effect on climate and on depleting ozone in the layer above us that protects us from harmful UV radiation. For us to understand the environmental impacts of megaconstellations, we need to know their emissions.”

The researchers compiled information from multiple disparate sources like space agency databases, academic studies, launch providers, YouTube launch livestreams, and online databases maintained by space enthusiasts, to construct a 3D database of emissions for rocket launches and spacecraft re-entries.

The inventory covered three years, representing the dawn of the satellite megaconstellation era, from 2020 to 2022, and tracked which emissions were from megaconstellations.

According to the study, the proportion of emissions from satellite megaconstellations accounted for almost half (40%) of carbon emissions, such as black carbon (soot) and carbon dioxide, from all launches in 2022, as most megaconstellation launches use SpaceX’s Falcon rockets that are propelled by carbon-containing kerosene fuel.

Particle emissions from re-entering megaconstellation satellites and rockets in 2022 were also found to be similar to the natural injection from meteors.

There are also other concerns. Professor Eloise Marais, co-author of the study, said, “One of the surprising outcomes is that we estimate a steady and worrying increase in the amount of material falling back to Earth, posing a threat to us. We estimate as much as 2000 tonnes of material may have returned to Earth in 2022.”

Looking ahead, the group aims to use the database in an atmospheric chemistry model to understand the environmental impact of satellite megaconstellations and hopes that other researchers will do the same.

“We have created this database to be as accessible as possible to other scientists to use in their atmospheric chemistry and climate models”, said Connor. “There is almost no current regulation on the environmental impacts of megaconstellations, so calculating these will be vital for policymakers.”

Published in the journal Nature Scientific Data, the research was led by Dr Connor Barker and Professor Eloise Marais from UCL, in collaboration with Dr Jonathan McDowell from the Harvard-Smithsonian Center for Astrophysics.