Image based relative motion estimation around a celestial body

A novel way to estimate the relative motion between a spacecraft and a surface of a celestial body using image correlation technique in frequency domain is discussed. An optical navigation, especially those for estimating the relative motion to the surface of the target body, plays essential role when a spacecraft touches down on a small celestial body, e.g. an asteroid, because detection and cancellation of the relative motion, especially the lateral one, fully depends on it. This paper discusses how to est mate the relative motion with a monocular video camera when the spacecraft approaches so close to the target that its image overflows the camera's field of view. The proposed algorithm estimate the relative translational motion and the rolling motion about the camera axis in such a case without using any landmarks. The numerical simulation shows that the translational motion can be detected with an accuracy of 0.1% of the altitude of spacecraft, and rolling motion within 2 degree with that of 0.3 degree.