Simultaneous localization and reconstruction from centroid correction for unexplored ellipsoidal asteroids during the approach phase

When approaching an asteroid, it is vital to reconstruct the target shape model and estimate the relative positions of the spacecraft and target. When the target is far from the spacecraft, image-based navigation utilizes the positions of the target centroid on the images for localization. However, the lack of illumination in imaging may introduce errors in the centroid positions and reduce localization accuracy. This paper proposes the simultaneous localization and reconstruction from centroid correction (SLRCC) method, which uses the target shape model to correct the centroid positions and refine the localization. The shape model requires relative positions to be reconstructed. The accuracy of the target reconstruction is affected by the accuracy of the relative positions. Therefore, it is necessary to design a pipeline that iteratively refines the localization and reconstruction reciprocally. This paper proposes a novel evaluation metric based on a comparison of the reprojected images with the observed images. Simulations targeting Eros and Itokawa are presented and analyzed to test the proposed solution. The effects of the illumination direction, line-of-sight direction, and asteroid rotation direction on the localization and reconstruction results are also investigated. Finally, a Monte Carlo simulation is performed to verify the reliability of the method proposed in this paper.