15:00 〜 15:15
[PPS03-23] Investigations of Dynamics of Binary Asteroid System and Non-Gravitational Effects with Hera Mission
キーワード：Heraミッション、DARTミッション、小惑星、ディディモス、ディモルフォス、熱物理
The European spacecraft Hera will be scheduled for launch in 2024 and arrival at a binary asteroid, (65803) Didymos and Dimorphos in 2027. ISAS/JAXA will provide the Hera mission with a thermal infrared imager (TIRI) and perform the thermal imaging of the binary asteroid. The TIRI team is planning to determine the thermophysical properties of the asteroids and conduct the detailed characterization of the artificial impact crater excavated by the DART spacecraft.
Our team will also contribute to working group activities of the Hera science team and provide high-level products from Hera's observation data. One of the working groups, the Non-Gravitational Acceleration (NGA) team is in charge of investigating the binary YORP (BYORP) effect on the asteroids' system. BYROP is the thermally induced acceleration or deceleration on a tidally locked satellite around a primary asteroid, which may cause a secular change in the semi-major axis and eccentricity of the mutual orbit (Ćuk and Burns, 2005; McMahon & Scheeres, 2010). The group of the University of Pisa aims to detect the changes in the orbit and spin parameters of the primary and secondary from the precise orbit determination (Zannoni et al., 2018). The ISAS team and collaborators will contribute with thermal observation and modeling. Some thermophysical models have been developed for the Hayabusa2 mission (e.g., Takita et al., 2017; Senshu et al., in prep.; Kanamaru et al., 2021), and these models will be improved and integrated for the Hera mission. The thermal force and torque on the asteroids should be simulated by a thermophysical model tuned based on the intensity distribution of the thermal radiation observed by TIRI.
Comparison of the results of the orbit determination with the thermal observations and modeling will reveal the dynamical evolution of the binary asteroids. From the magnitude of the BYORP effect, we can estimate the dynamical lifetime of the binary system. If no change in orbit could be observed, it is possible that the BYORP effect that tends to shrink the mutual orbit is balanced by a tidal effect that expands the orbit (Walsh and Jacobson, 2015. in Asteroids IV). These investigations will be helpful for understanding the formation and evolution processes of binary asteroids that account for 15% of the asteroid population.
Our team will also contribute to working group activities of the Hera science team and provide high-level products from Hera's observation data. One of the working groups, the Non-Gravitational Acceleration (NGA) team is in charge of investigating the binary YORP (BYORP) effect on the asteroids' system. BYROP is the thermally induced acceleration or deceleration on a tidally locked satellite around a primary asteroid, which may cause a secular change in the semi-major axis and eccentricity of the mutual orbit (Ćuk and Burns, 2005; McMahon & Scheeres, 2010). The group of the University of Pisa aims to detect the changes in the orbit and spin parameters of the primary and secondary from the precise orbit determination (Zannoni et al., 2018). The ISAS team and collaborators will contribute with thermal observation and modeling. Some thermophysical models have been developed for the Hayabusa2 mission (e.g., Takita et al., 2017; Senshu et al., in prep.; Kanamaru et al., 2021), and these models will be improved and integrated for the Hera mission. The thermal force and torque on the asteroids should be simulated by a thermophysical model tuned based on the intensity distribution of the thermal radiation observed by TIRI.
Comparison of the results of the orbit determination with the thermal observations and modeling will reveal the dynamical evolution of the binary asteroids. From the magnitude of the BYORP effect, we can estimate the dynamical lifetime of the binary system. If no change in orbit could be observed, it is possible that the BYORP effect that tends to shrink the mutual orbit is balanced by a tidal effect that expands the orbit (Walsh and Jacobson, 2015. in Asteroids IV). These investigations will be helpful for understanding the formation and evolution processes of binary asteroids that account for 15% of the asteroid population.