A New Global Reference Frame for Mars From Tianwen-1 Moderate Resolution Images

The Moderate Resolution Imaging Camera (MoRIC) onboard the Tianwen-1 orbiter, China’s first Mars exploration mission, is a frame-imaging color camera. As of July 25, 2022, it has acquired a total of 14757 multiview stereo images covering the entire Martian surface. This letter proposes a scheme to construct a new global reference frame for Mars with a spatial resolution of several tens of meters using MoRIC images. It addresses critical issues, including on-orbit stereo imaging, tie points control network establishment, and global adjustment. Based on the photogrammetric global bundle adjustment technology with image data, the parameters, such as the internal and external orientation elements of the MoRIC images, have been significantly optimized. This has enabled high-precision positioning of images on the global scale of Mars, with a root mean square (rms) pixel residual of 0.9 pixels for tie points. A global orthophoto mosaic with a spatial resolution of 76 m and a geodetic control network have been established as a new Mars reference frame, providing a crucial foundational data for both Mars scientific exploration and engineering implementation.