14:15 〜 14:30
[MZZ40-03] Concept study of small-body exploration mission for planetary defense
キーワード：太陽系探査、小天体、プラネタリーディフェンス
Planetary defense is an international disaster prevention science that responds to the impact of small bodies on Earth. Planetary defense activities begin with discovering near-Earth objects (NEOs) through telescope observations and tracking them for precise orbit determination. It is also important to understand the physical properties of the NEOs using spacecraft. If a NEO is expected to collide with Earth, we will consider changing its orbit by colliding spacecraft with the NEO to avoid collision. If the collision is inevitable, we will evacuate people living where the NEO may fall. Planetary defense activities also include outreach activities regarding disasters caused by small-body collisions.
The essential factor (or information) of the NEOs in avoiding collision with Earth is the momentum enhancement factor β due to an impact. The β is the ratio of the net impact ejecta momentum to the momentum given by an impactor, i.e., space craft. While β was estimated to be 2.2 to 4.9 during the impact of the DART mission [1], β depends on the impact angle, the target's porosity, density, and strength [2]. Thus, an exploration mission is necessary for the better knowledge of NEOs.
Crater scaling laws for impact crater formation have been proposed from various laboratory experiments, numerical experiments, and analytical methods [3].Telescope observations of small bodies can estimate a NEO's orbit, diameter, albedo, rotation state, shape, and asteroid spectral type by combining optical, radar, and infrared (spectroscopic) observations. However, telescopic observation cannot directly determine the NEO's bulk density and surface strength. These physical properties change the final crater size on Earth [3]. In particular, it is important for planetary defense to understand the physical properties of NEOs with a diameter of 100 to 300 m. Since these sized NEOs are hard to measure using telescope, we need an exploration mission. In this presentation, we will summarize and discuss the types of a small body exploration mission that will contribute to future planetary defense activities.
References: [1] Cheng, A. F., et al. (2023). Nature, 616(7957), 457-460. [2] Wakatsuki, Y., et al. (2023). International Journal of Impact Engineering, 180, 104710. [3] Housen, K. R., & Holsapple, K. A. (2011). Icarus, 211(1), 856-875.
The essential factor (or information) of the NEOs in avoiding collision with Earth is the momentum enhancement factor β due to an impact. The β is the ratio of the net impact ejecta momentum to the momentum given by an impactor, i.e., space craft. While β was estimated to be 2.2 to 4.9 during the impact of the DART mission [1], β depends on the impact angle, the target's porosity, density, and strength [2]. Thus, an exploration mission is necessary for the better knowledge of NEOs.
Crater scaling laws for impact crater formation have been proposed from various laboratory experiments, numerical experiments, and analytical methods [3].Telescope observations of small bodies can estimate a NEO's orbit, diameter, albedo, rotation state, shape, and asteroid spectral type by combining optical, radar, and infrared (spectroscopic) observations. However, telescopic observation cannot directly determine the NEO's bulk density and surface strength. These physical properties change the final crater size on Earth [3]. In particular, it is important for planetary defense to understand the physical properties of NEOs with a diameter of 100 to 300 m. Since these sized NEOs are hard to measure using telescope, we need an exploration mission. In this presentation, we will summarize and discuss the types of a small body exploration mission that will contribute to future planetary defense activities.
References: [1] Cheng, A. F., et al. (2023). Nature, 616(7957), 457-460. [2] Wakatsuki, Y., et al. (2023). International Journal of Impact Engineering, 180, 104710. [3] Housen, K. R., & Holsapple, K. A. (2011). Icarus, 211(1), 856-875.