Color marker employed in conjunction with space robots for on-orbit assembly has been developed. The marker consists of three printed discs with different colors. When used for on-orbit assembly, markers will be attached at the proximity of the connection mechanisms of assembly segment for large space structures. The distance and attitude of the segments can be measured by the positional relationship between the color discs of the marker. From the evaluation test, it has been verified that the performance of the measuring system with the color markers can meet the requirement of the space robot arms.
An algorithm is developed for estimating the motion (relative attitude and relative position) of large pieces of space debris, such as failed satellites. This algorithm is designed to be used by a debris removal system which would perform various operations on space debris such as observation, investigation, capture, repair, refuel and de-orbit. The algorithm uses a combination of stereo vision and 3D model matching, applying the ICP (Iterative Closest Point) algorithm, and uses time series of images to increase the reliability of relative attitude and position estimates. To evaluate the algorithm, a visual simulator is prepared to simulate the on-orbit optical environment in terrestrial experiments, and the motion of a miniature satellite model is estimated using images obtained from this simulator.