Bundle adjustment of Hayabusa2's ONC images and controlled color mosaic map of Ryugu

TL;DR

This paper presents a bundle adjustment method for refining the geometry of Hayabusa2's ONC images, enabling the creation of accurate global and regional mosaic maps of asteroid Ryugu for scientific analysis.

Contribution

It introduces a photogrammetric bundle adjustment technique to improve image geometry and produce precise mosaic maps from spacecraft images of Ryugu.

Findings

Refined image geometry for high-resolution images

Created accurate global and regional mosaic maps

Enhanced data for scientific research on Ryugu

Abstract

JAXA's Hayabusa2 mission successfully returned samples from the asteroid Ryugu in December 2020. It executed two touchdowns to collect the surface and subsurface materials, one close to the crater created by an artificial impactor. The onboard camera system, Optical Navigation Camera (ONC), with two wide-angle cameras and one narrow-angle camera with seven color filters, was crucial for mapping geomorphology and composition such as hydrated minerals during navigation and scientific observation. More than 8,300 images revealed Ryugu's spinning-top shape and boulder-covered surface. However, most high-resolution images captured during descent/touchdown operations lacked precise location data and camera position/orientation information. Image geometry was refined using photogrammetric bundle adjustment. This method enabled the refinement of all high-resolution images captured during descent/touchdown operations. Furthermore, map-projected GeoTIFF images in GIS format containing geographic metadata were created for all ONC images, and these were integrated to construct global and regional mosaic maps. To facilitate scientific research on Ryugu, these refined image geometry information, maps, and mosaics are publicly available via https://doi.org/10.7910/DVN/WW3IH0