Satellite megaconstellations and collective casualty risks

• Megaconstellations of thousands of satellites are being launched, and will reenter the atmosphere at end of life to avoid generating space debris. • Satellite designers may aim for their satellites to demise entirely, but there is considerable uncertainty in the degree to which total ablation can be achieved. • If a satellite does not burn up entirely, it creates a casualty risk. • Many existing casualty risk thresholds are calculated per satellite, while others apply vastly different thresholds to address collective casualty risk. • We model the reentry of eleven megaconstellations, finding a 40% collective risk of on-ground casualties if satellites do not burn up entirely.