Global 3D rocket launch and re-entry air pollutant and CO2 emissions at the onset of the megaconstellation era

Abstract

Satellite megaconstellation (SMC) missions are spurring rapid growth in rocket launches and anthropogenic re-entries. These events inject pollutants and carbon dioxide (CO₂) in all atmospheric layers, affecting climate and stratospheric ozone. Quantification of these and other environmental impacts requires reliable inventories of emissions. We present a global, hourly, 3D, multi-year inventory of air pollutant emissions and CO₂ from rocket launches and object re-entries spanning the inception and growth of SMCs (2020-2022). We use multiple reliable sources to compile information needed to build the inventory and conduct rigorous and innovative cross-checks and validations against launch livestreams and past studies. Our inventory accounts for rocket plume afterburning effects, applies object-specific ablation profiles to re-entering objects, and quantifies unablated mass of objects returning to Earth. We also identify all launches and objects associated with SMC missions, accounting for 37-41% of emissions of black carbon particles, carbon monoxide, and CO₂ by 2022. The data are provided in formats for ease-of-use in atmospheric chemistry and climate models to inform regulation and space sustainability policies.

Fig. 1

Workflow to generate 3D hourly global air pollutant and CO₂ emissions from rocket launches and object re-entries for 2020–2022.

Fig. 2

Annual propellant mass consumed by all rockets in each atmospheric layer in 2020–2022. Colours distinguish 2020 (blue), 2021 (red), and 2022 (green). Hatched areas demarcate the SMC portion.

Fig. 3

The mapped distribution of re-entering objects (a) and mass (b) in 2022. In (a) the left map is coloured according to the location constraint and the right bar chart sums the number of randomly geolocated objects in 15° latitude bands. The re-entry mass in (b) is gridded to a 4° latitude × 5° longitude horizontal grid and is on a log scale. Grey grid cells in (b) denote no re-entry mass.

Fig. 4

Vertical profiles of Cl_y emission indices from 0 to 80 km. Symbols are averaged data from studies of chlorine mass partitioning^– and the dashed lines are fits to the data for HCl (blue, Eq. (4)), Cl (red), and Cl₂ (black).

Fig. 5

Vertical distribution of air pollutant and CO₂ emissions from rocket launches and object re-entries in 2022. Emissions totals are in Fig. 6.

Fig. 6

Annual rocket launch and re-entry air pollutant and CO₂ emissions in 2020–2022. Panels are for all launches and object re-entries (a) and for SMC missions only (b). H₂O and CO₂ emissions are divided by 10 to fit within the plot range.

Fig. 7

Evaluation of vertical profiles of propellant consumption. Profiles are propellant burned in 5-km bins up to 80 km and include those used in this work (green), reported in the literature (blue), and obtained from launch livestreams (orange) (see text for details). Shading distinguishes the troposphere (grey), stratosphere (blue), and mesosphere (green).