Orbital re-entries of human-made space objects: drawbacks for the upper atmosphere and the safety of people

The controlled and uncontrolled orbital re-entries occurred from 2010 to 2023 were reviewed. Excluding five Space Shuttle orbiters, the total mass re-entered into the atmosphere exceeded 4200 metric tons. In the five-year period 2019-2023, controlled spacecraft re-entries accounted for nearly 20% of the returned mass, against 45% associated with uncontrolled re-entries of intact objects and large debris, and 35% with controlled re-entries of Falcon 9 second stages. In 2023, the orbital re-entry mass dispersed as gas and particulate in the upper atmosphere was close to 600 metric tons. The ground casualty probability associated with the uncontrolled re-entry of satellites, orbital stages and large debris varied, on an annual basis, from 0.8% in 2010 to 3.5% in 2023, assuming the complete demise of all objects of less than 300 kg. Always in 2023, 70% of the casualty probability was associated with orbital stages, 20% with satellites and 10% with large fragments.