Guidance law of impacting small bodies using zero-effort-miss(ZEM) steering

Impacting target body directly is a new method to explore the small bodies such as the comets and the asteroids, and which was carried out by NASApsilaS Deep Impact mission. In this paper, an autonomous end game guidance law of impacting asteroids is discussed. Due to the pulsed thrust of spacecraft actuator, a pulsed guidance law is established based on the zero-effort-miss steering. Then, in order to execute the guidance law autonomously, the navigation error is described in the B-plane by navigation error ellipse. So, the time of executing trajectory correction maneuver (TCM) is determined by comparing the ZEM with navigation error. It will be shown that this technique has the advantage of better precision and can execute the guidance law autonomously which can reduce the fuel consumption. A typical numerical example is given here. And with the comparison to the guidance law applied in Deep Impact mission, results show that this end game guidance law can obtain better precision with less fuel consumption.