Abstract: Aiming at solving the close-range relative navigation problem for onorbit serving (OOS) missions of CubeSats, a vision sensor design for measuring the relative pose was proposed. In order to circumvent the complex light conditions in space, a multi-layer stereo marker was designed. The LEDs with a wavelength of 850 nm were selected as the illuminators of the stereo marker. An infrared narrow band-pass filter that only let 850 nm length waves pass was added in front of the camera lens to improve the imaging quality of the stereo marker. An iterative direct solution (IDS) was derived for the relative pose estimation. This algorithm used the depth information provided by the non-coplanar points in the stereo marker to obtain an initial relative pose. The Haralick iterative algorithm was then introduced to optimize the initial relative pose. An experiment platform with six degree-of-freedom was built to test the performance of the vision sensor. The results show that the vision sensor can overcome the interference of ambient light. The accuracy of the proposed IDS algorithm for pose estimation is better than those of the classical P3P algorithm and EPnP algorithm. 

Key words: CubeSat, relative pose measurement, vision-based navigation (VBN), marker, on-orbit serving (OOS)