In a second study on “the orbital debris collision hazard for proposed satellite constellations”, D. Steel estimated that the OneWeb constellation could lead to one catastrophic collision every 25 years and that the Space X Starlink constellation (based on 4,025 satellites) could lead to as much as one catastrophic collision every 20 months. This estimation is consistent with another study by NASA which attempted to calculate and forecast risks of collisions for different constellation scenarios, taking also into account the level of compliance with existing debris mitigation rules.