[P-PS03] 太陽系小天体研究：現状の理解と将来の展望

[PPS03-28] 模擬画像データを用いた小惑星Ryuguの自転情報の推定

*西川 直輝¹、平田 直之¹、平田 成²、田中 小百合¹、渡邊 誠一郎³、石原 吉明⁴、田中 智⁴、山口 智宏⁴、三浦 昭⁴、山本 幸生⁴ (1.神戸大学、2.会津大学/宇宙情報科学クラスター、3.名古屋大学、4.ISAS/JAXA)

キーワード：はやぶさ2、リュウグウ、自転情報

The spin-axis orientation and rotation rate for asteroid Ryugu are essential for the Hayabusa2 mission plan such as landing site selection and scientific researches. Unfortunately, ground-based observations cannot constrain those accurate values because of insufficient light curve quality owing to Ryugu’s spherical shape. Therefore, we need to constrain them using images obtained by the optical navigation camera (ONC) onboard Hayabusa2. In the presentation, we will discuss a suitable way to obtain accurate spin-axis orientation and rotation immediately. Then, we utilized images of a vertical asteroid Ryugoid generated for a dry-run test of LSS sequence to simulate the real RYUGU, assumed that the rotational properties of Ryugoid were unknown, estimated rotational properties for Ryugoid, and evaluated its accuracy based on the comparison with the true value. Although Hayabusa2 plans to observe Ryugu in 4 sequences (approach phase, boxA, bocC, and middle altitude), we focused on the image date acquired in approach phase and boxA because we need to determine the rotational properties immediately. Then, we used software called StereoPhotoclinometry (SPC). SPC improves the spacecraft position, spacecraft pointing, and the surface topography of the asteroid, which enable us to solve the rotational properties.