Fig. 2

Geometric correction procedure. The figures of upper and bottom rows were generated in the step described in the subsection of Projection from image to shape in the method section as follows: “observed image” \(\rightarrow\) “projected onto the shape model” \(\rightarrow\) “reproduced image.” Minimizing the difference between the observed image and the reproduced image derived the best-fit Euler angles \(\theta _y\) and \(\theta _x\) using Eq. (6), iteratively. The upper row shows the derived figures used by the fitting Euler angles as the initial value (previous study), and the bottom row shows the derived figures fitted using the best-fitted one (this study). The residual of the observed image and the reproduced image mean the out of projection, shown in grayscale (right figures). Although the overhang of the projection was at most 7 pixels or about 35 m (upper row) before the correction, the geometric correction achieved the projection accuracy within one pixel after the correction (bottom row). The observed temperature at the asteroid limb position was not fitted because the pixel value at the limb included not only Ryugu temperatures but also space background