We previously introduced a global image of asteroid Ryugu, but the Hayabusa2 Project shape model team have also created three-dimensional models of the asteroid. The asteroid was measured using images captured with the ONC-T (Optical Navigation Camera - Telescopic) to form a "shape model" of Ryugu. The shape of Ryugu is fundamental information when considering the formation history of the asteroid and it is also key to future operations by Hayabusa2.

The shape model team have initially used images taken during Hayabusa2's arrival at the asteroid to create the first three-dimensional shape models of Ryugu. This shape models were used in Figures 1 and 2 to show animations of the rotating Ryugu generated using computer graphics.

Figure 1: Shape model of Ryugu by the University of Aizu.
Image credit ※1: University of Aizu, Kobe University (shape model creation), Auburn University (video creation), JAXA.

Figure 2: Shape model of Ryugu by Kobe University.
Image credit ※2: Kobe University, University of Aizu (shape model creation), Auburn University (video creation), JAXA

The shape model team created shape models from the same image data in two different ways. The first method shown in Figure 1 is a type of stereoscopic technique called "Structure-from-Motion" (SfM). This is the same method that is used to create terrain and building shapes from aerial images that are commonly seen when taken by a drone. Figure 2 shows the shape model created with a second method known as "stereophotoclinometry" (SPC). This technique was also used to model the shape of asteroid Itokawa, the destination of the first Hayabusa spacecraft. By comparing the two shape models, we can assess how accurately the shape of Ryugu has been replicated. Although the two models show minor differences, both depict a global shape similar to the bead on an abacus, with recesses that look like craters and boulders of rock on the surface.

If higher resolution images of Ryugu are obtained in future observations, the three-dimensional shape of the asteroid can be clarified in greater detail.