Uncontrolled re-entries: the need to mitigate the increasing risk on ground due to the re-entry of large spacecraft and orbital stages, and to establish an aggregate re-entry risk for constellations

The casualty probability associated with the uncontrolled re-entry of spacecraft is still quite low, of the order of 0.8% in 2022, but the disposal of satellites from the current planned mega-constellations could significantly increase the likelihood of casualties on the ground in the coming years. In fact, even if the value of the casualty expectancy associated with each satellite of a constellation is below the alert threshold of 10-4, if several thousands more satellites were to re-enter without control every year, the casualty probability would probably reach unacceptable values for safety on the ground and in the airspace. Therefore, it would be necessary to establish an aggregate re-entry risk for constellations, by adopting, for instance, an annual limit for the casualty expectancy value that the constellation shall not exceed.