Earth-orbit crossing asteroids constitute a threat to human civilisation. Space missions can mitigate the risk. One example of a planetary defence mission feasible with existing technology is deflection via high velocity impact: A spacecraft is sent to a hazardous asteroid and hits it a high relative speed. This changes the asteroid's orbit such it then later flies harmlessly past the Earth instead of impacting.The reaction time is vital for the success of a planetary defence mission. The earlier a mission can be launched to a hazardous object, the more effective it can be. Launching such missions from the Earth surface is not efficient. Years would be lost in preparation. Also, launch from the Earth surface leads to high cost and constrained mission profiles. It is much more advantageous to already have spacecraft operational and waiting in a parking orbit, from they can be deployed.The choice of the parking orbit should take into account existing infrastructure. Currently, NASA is envisaging the Lunar Orbital Platform-Gateway (LOP-G), formerly known as the Deep Space Gateway, a permanently manned hub and space station in an orbit above the far side of the Moon. This location is far removed from the Earth and therefore energetically close to Earth escape. It is ideal to support operations from and to the lunar surface and deep space. The LOP-G can also serve as parking location for planetary defence missions. In the course of the study, the following can be analysed:- Options for in-orbit parking of planetary defence spacecraft, making use of existing LOP-G infrastructure- Rapid Earth escape from the LOP-G orbit - Maximisation of synergies with the LOP-G- Spacecraft design allowing use not only for planetary defence, but also for scientific research or to support manned spaceflight missionsAll issues are highly complex and strongly interdisciplinary, involving orbital mechanics, system engineering, space politics, planetary science and space situational awareness.
