Gravity Field and Orbital Mechanics within the Brillouin Sphere of a Small Body

• Project/Area Number: 20K14952
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 24010:Aerospace engineering-related
• Research Institution: Chiba Institute of Technology (2021-2022); Japan Aerospace EXploration Agency (2020)
• Principal Investigator: Kikuchi Shota 千葉工業大学, 惑星探査研究センター, 特別研究員(PD) (90830068)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Project Status: Discontinued (Fiscal Year 2022)
• Budget Amount: ¥3,770,000 (Direct Cost: ¥2,900,000、Indirect Cost: ¥870,000); Fiscal Year 2022: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000); Fiscal Year 2021: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000); Fiscal Year 2020: ¥1,690,000 (Direct Cost: ¥1,300,000、Indirect Cost: ¥390,000)
• Keywords: 小天体 / 探査機 / 重力場 / 太陽光圧 / 摂動 / 軌道運動 / 小惑星探査 / 軌道力学 / 天体内部構造 / 内部構造

Outline of Research at the Start

小惑星や彗星などの小天体近傍では、歪な形状に起因する重力の不均一成分（高次重力）によって、物体の運動が強い外乱を受ける。特に、小天体表面近くのブリルアン球（天体の外接球）内では高次重力が発達し、物体の運動は複雑な様相を示す。本研究の目的は、小天体のブリルアン球内での重力場とその重力場に支配される探査機や浮遊ダストの運動を解明することになる。本研究では、はやぶさ２で観測された小惑星リュウグウ近傍でのフライトデータを用いて、小天体のブリルアン球内における重力場と軌道運動を実証的に解明する。

Outline of Final Research Achievements

Within a Brillouin sphere near the surface of a small body, the motion of an object is strongly perturbed due to the non-uniform gravity field of the body. This research conducted empirical studies on the gravity field and orbital motion within the Brillouin sphere using the flight data of Hayabusa2 in the vicinity of the asteroid Ryugu. The primary results are as follows: 1) estimation of the gravity field of Ryugu based on the asteroid shape model and the orbital motion of artificial markers, 2) precise reconstruction of the Hayabusa2 trajectories based on optical and altimetric data, and 3) derivation of the analytical solution of frozen orbits that are stable even under strong perturbations caused by the gravity field of a small body and the solar radiation pressure.

Academic Significance and Societal Importance of the Research Achievements

はやぶさ２がリュウグウ近傍で取得したデータに基づく本研究の成果により、実際の小天体近傍での重力場や物体の運動に関する貴重な知見が得られた。小天体表面の極近傍における運動は、探査機着陸や小型ロボット分離の誘導精度を大きく左右する。また、小天体ダストの表層付近での運動は、小天体形成過程や探査機安全性に影響を与える。したがって、今後の小天体探査における、より高度な探査機運用や取得データに基づく科学成果の最大化という観点で、本研究は工学的にも理学的にも極めて意義深い。より広い視点では、小天体探査を通じた太陽系や生命の起源解明に貢献し得る成果である。

Research Products

• [Journal Article] Hayabusa2 radio science investigation (2022)
  • Author(s): Ikeda Hitoshi, Takeuchi Hiroshi, Kikuchi Shota, Mimasu Yuya, Ogawa Naoko, et al.
  • Journal Title: Hayabusa2 Asteroid Sample Return Mission: Technological Innovation and Advances Volume: 1 Pages: 387-399
  • DOI: 10.1016/b978-0-323-99731-7.00019-2
  • ISBN: 9780323997317
  • Peer Reviewed
• [Journal Article] Touchdown operation planning, design, and results (2022)
  • Author(s): Terui Fuyuto, Kikuchi Shota, Takei Yuto, Mimasu Yuya, Sawada Hirotaka, Saiki Takanao, and Tsuda Yuichi
  • Journal Title: Hayabusa2 Asteroid Sample Return Mission: Technological Innovation and Advances Volume: 1 Pages: 259-289
  • DOI: 10.1016/b978-0-323-99731-7.00014-3
  • ISBN: 9780323997317
  • Peer Reviewed
• [Journal Article] Frozen Orbits Under Radiation Pressure and Zonal Gravity Perturbations (2021)
  • Author(s): Kikuchi Shota, Oki Yusuke, and Tsuda Yuichi
  • Journal Title: Journal of Guidance, Control, and Dynamics Volume: 44 Issue: 11 Pages: 1924-1946
  • DOI: 10.2514/1.g005564
  • Peer Reviewed / Open Access
• [Journal Article] Hayabusa2 pinpoint touchdown near the artificial crater on Ryugu: Trajectory design and guidance performance (2021)
  • Author(s): Kikuchi Shota, Saiki Takanao, Takei Yuto, Terui Fuyuto, Ogawa Naoko, et al.
  • Journal Title: Advances in Space Research Volume: 68 Issue: 8 Pages: 3093-3140
  • DOI: 10.1016/j.asr.2021.07.031
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Ballistic Deployment of the Hayabusa2 Artificial Landmarks in the Microgravity Environment of Ryugu (2021)
  • Author(s): S. Kikuchi, N. Ogawa, O. Mori, T. Saiki, Y. Takei, F. Terui, G. Ono, Y. Mimasu, K. Yoshikawa, S. Van Wal, H. Takeuchi, H. Ikeda, A. Fujii, Y. Takao, T. Kusumoto, N. Hirata, N. Hirata, K. Shirai, T. Kouyama, S. Kameda, M. Yamada, S. Nakazawa, M. Yoshikawa, S. Tanaka, S. Sugita, S. Watanabe, and Y. Tsuda
  • Journal Title: Icarus Volume: 358 Pages: 114220-114220
  • DOI: 10.1016/j.icarus.2020.114220
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Presentation] Preliminary Mission Analysis for the Hayabusa2 Extended Mission in the Vicinity of 1998 KY26 (2022)
  • Author(s): Shota Kikuchi, Yuya Mimasu, Takanao Saiki, Yuto Takei, Hitoshi Ikeda, Yuichi Tsuda
  • Organizer: 33rd International Symposium on Space Technology and Science
  • Int'l Joint Research
• [Presentation] Image-based Estimation of the Attitude and Orbital Motion of Hayabusa2's Deployable Camera (DCAM3) around Ryugu (2022)
  • Author(s): Shota Kikuchi, Kei Shirai, Ko Ishibashi, Koji Wada, Rie Honda, et al.
  • Organizer: 33rd International Symposium on Space Technology and Science
  • Int'l Joint Research
• [Presentation] 高速自転小惑星1998 KY26の軌道変更についての実現可能性検討 (2021)
  • Author(s): 菊地翔太
  • Organizer: 第31回アストロダイナミクスシンポジウム