Space-based target detection technology has become the frontier technology of space research. Because deep space target is far away from the detector

its image shapes a spot

it is difficult to be distinguished from the false targets such as stars and planet by shape features. Star tracker can effectively exclude the stars in false targets due to its navigation satellite library. According to difference of law of motion of true and false targets in right ascension coordinate system

combined with attitude matrix

the tracker can recognize the true target from complex starry background

so as to achieve the purpose of safety protection. Simulation results verify the validity of the proposed method.