Abstract: Aiming at the situation that the collimating light path is blocked when measuring the normal direction of plane mirror and cubic mirror on spacecraft, an oblique observation method is proposed. This method is to set two theodolites at symmetrical positions on both sides of the mirror normal, so that the two theodolites can observe each other’s light, so as to finally obtain the mirror normal direction. Firstly, the measurement object is described, and then the measurement method based on mirror normal collimation and oblique observation are described in detail. Finally, the measurement comparison test is carried out according to the two measurement methods, and the observation data of theodolites and calculation results are given. Through several experimental data statistics, the difference between oblique observation results and collimation measurement results is in the order of angular seconds, which meets the requirements of Spacecraft test requirements, and can effectively solve the problem of mirror normal direction measurement when the collimation direction of reference mirror on spacecraft is blocked.

Key words: Spacecraft, Measurement, Mirror, Normal