Shape models, their derivatives, and relating data and tools of the asteroid Ryugu used in the paper "Hayabusa2 observations of the top-shape carbonaceous asteroid 162173 Ryugu" by Watanabe et al. (2019).


This archive contains shape models and their derivatives of the asteroid Ryugu, together with tools, or pointers to tools used to produce the data. This archive prepared to reproduce the results presented in the paper "Hayabusa2 observations of the top-shape carbonaceous asteroid 162173 Ryugu" by Watanabe et al. (2019). It is provided "as is" without warranty of any kind, either express or implied.

Shape models

The 3M polygon model (SHAPE_SFM_3M_v20180804.obj) is the initial output of our shape modeling procedure, and the 800k, 200k and 49k polygon models are reduced version. They are stored in in the Wavefront OBJ format. SHAPE_SFM_49k_v20180804.dat is the model identical to the 49k model (SHAPE_SFM_49k_v20180804.obj), but converted to use our gravitational analysis with GFandSlope.

Derivatives from the shape models

Gravity_SHAPE_SFM_49k_v20180804_XXXX_1200a.txt, where XXXX is the rotation period. The file contains an ASCII table of gravity potential, slope and other auxiliary values computed by GFandSlope (see below) for every polygon plate of the 49k polygon shape model at a given rotation period and with an assumed uniform density of 1200 kg/m^3.

Differences in topography between the SfM model and the SPC model computed for every polygon plate of the 3M polygon model appeared in Fig. S2. Expressed in km.

List of informations (polygon center coordinate, area, latitude and longitude, and radius from the origin, see the 1st line of the file for detail) of every polygon plates consisting the 3M shape model. It was used analysis on surface tilt angles. See below and README_TiltAngleAnalysis.docx for detailed usage of the file.

ONC images

ONC images and related files used in Fig. 1 and 4A. See README_Fig4.docx for detailed description of Fig. 4A. General description of the ONC data is found at


Package Tools (Not included in this archive)

Agisoft PhotoScan was used to produce the SfM shape models. It is a commercial software by Agisoft, available at the Agisoft website ( PhotoScan currently renamed to Agisoft MetaShape 1.5.

The SPC code was used to produce SPC shape models. It is developed and maintained by R. Gaskell and Planetary Science Institute. Distribution of the SPC software is legally restricted by the US International Traffic in Arms Regulation. US citizens (only) may request an SPC research licence, with appropriate restrictions, at .

GMT (Generic Mapping Tools) is used to produce Fig. S4 from outputs of GFandSlope. GMT is available at the project site (

AiGIS is a visualization tool for small body exploration data developed by the University of Aizu, available at the developer’s website ( It was used to produce pictures appeared in Figs. 2, 3B, and S2.

Script and tools internally developed by the authors

C++ tool to compute gravitational potential and slope of the asteroid surface with the given rotational period and density.

How to Compile

$ g++ GFandSlope.cpp
Attached header files (GF.h and vector3.h by S. Zenitani, 2001) should be placed at the same directory. Also it requires the SPICE toolkit developed and distributed by NAIFJPLNASA ( Usage
It will work by giving a shape model, rotation period (expressed in Hours), and density (expressed in the SI unit) as arguments.

Jupyter Notebook script to compute and plot statistical information of the slope and gravitational potential that calculated by GFandSlope. It was used to produce plots appeared in Fig. 2A and S5.

R script to compute surface tilt angles in Fig. S3. See README_TiltAngleAnalysis.docx for details.

ImageJ script to compute equatorial aspect ratio and the circularity of asteroid bodies in SM7 and Table S3. See README_ShapeAnalyses.docx for details.

The input files to ANSYS Mechanical APDL are available at

Auburn University ( ).

A tool to produce the safety index map in Fig. S7 is packaged in safety_index It requires a shape model in the STL format. The STL format shape model can be obtained by converting from the OBJ format shape models with MeshLab or other major shape model handling tools. See How_to_generate_safety_index maps.pdf for details of the tool.


This document was prepererd by Naru Hirata, the University of Aizu ( on Mar. 4, 2019.