Remote sensing images of Mars contain extensive information about its surface morphology, topography, and geological structure. This data is the basis for scientific research and exploration missions to Mars. Ahead of China’s first Mars exploration mission, a global/near-global imaging dataset of Mars with a spatial resolution of more than 1 km has been created using data from six advanced optical imaging systems obtained during various missions in Mars orbit.
However, as far as global color images are concerned, the resolution of the highest version of the Mars Viking Colorized Global Mosaic is about 232 m/pixel. There is a lack of global color images of Mars with high resolution at the scale of hundreds of meters. New data from the Tianwen-1 mission laid the foundation for the development of a high-resolution global color image map of Mars with high positional accuracy. As of July 25, 2022, the Tianwen-1 Moderate Resolution Imaging Camera (MoRIC) had completed 284 orbits during its remote sensing mission and captured 14,757 images with a spatial resolution of 57 to 197 meters.
The collected images covered the entire surface of Mars. At almost the same time, a total of 325 data strips in the visible and near-infrared ranges with a spatial resolution of 265 to 800 m were recorded by the Tianwen-1 Mars Mineral Spectrometer. Using the above data, Professor Li Chunlai of the National Astronomical Observatory of the Chinese Academy of Sciences and Professor Zhang Rongqiao of the Lunar Exploration and Space Engineering Center led the Tianwen-1 science team and their collaborators to carry out image data processing and global research on Mars mapping.
The research results were published in Science Bulletin. The study used bundle adjustment techniques to optimize the original orbital measurement data by treating Mars as an integrated adjustment network, reducing the misregistration between individual MoRIC images to less than one pixel, achieving “seamless” global image mosaicking at the pixel level. Overall image brightness and color consistency were ensured by color correction and global color uniformity.
The true color of the Martian surface was measured using the MMS on board the Tianwen-1 orbiter, creating a true color standard for the Martian surface and restoring the true color. The study produced and published a global color image dataset with a resolution of 76 m and a horizontal accuracy of 68 m and a map of Mars (Tianwen-1 Mars Global Color Orthomosaic 76 m v1). The Tianwen-1 Mars global color orthomosaic data product fills a gap in high-precision positioning of Mars global color imagery data products at tens of meters scale.
It is currently the highest-resolution global true-color imagery map of Mars, significantly improving the resolution and color reliability of commonly used global Mars images. This mapping product will serve as a new global Mars basemap, providing a high-quality geographic reference for international collaborators to conduct Mars imagery mapping at tens of meters, meters, and sub-meter scales to support subsequent Mars exploration missions and scientific research.
source:https://dx.doi.org/10.1016/j.scib.2024.04.045