Global 3D model reconstruction of Phobos integrating high-resolution imaging data from the Tianwen-1 mission
Abstract
Tianwen-1 was successfully launched in July 2020 and has been operating normally since entering its remote sensing exploration phase in February 2021. The High-Resolution Imaging Camera (HiRIC) aboard Tianwen-1 provided a valuable opportunity to observe Phobos. To address the relative scarcity of imaging data for the trailing hemisphere of Phobos, we first designed an observation strategy for Tianwen-1 and imaged this region using HiRIC. The resulting imagery covers the Öpik crater region, which lies near the center of the trailing hemisphere and serves as a representative area for assessing local reconstruction quality. Our objective is to integrate these new observations with historical imagery from multiple missions to reconstruct a global three-dimensional (3D) model of Phobos with high geometric accuracy. We developed a three-step incremental stereo-photogrammetric (SPG) processing strategy and applied it to 851 images from the Mars Express, Viking Orbiter, and Tianwen-1 HiRIC. The incorporation of Tianwen-1 HiRIC observations not only improves the overall geometric accuracy of the model but also enhances the reconstruction of the topography in the Öpik crater region on the trailing hemisphere. The resulting model also supports updated estimates of Phobos’ volume, surface area, and bulk density, which provide useful a priori information for planning future deep-space exploration missions.