An advanced predictive guidance law of impacting to small asteroids

which takes time of trajectory correction maneuvers and finally precision into account

is proposed.According to the special characteristics of high speed impact mission

the biases of navigation system is presented using error ellipse in the B-plane coordinate.The zero-effort-miss（ZEM） is obtained through the states of probe and target asteroid.The ZEM with navigation bias is compared to determine the time of execute the guidance law to eliminate the predictive error of impact.The results show that this strategy can not only save the fuel consuming

but also obtain a better precision.