講演情報
[PPS03-12]Current Status of DESTINY+ project and science
*荒井 朋子1、小林 正規1、石橋 高1、木村 宏1、平井 隆之1、岡本 尚也1、山田 学1、秋田谷 洋1、千秋 博紀1、和田 浩二1、吉田 二美2,1、スラマ ラルフ3、クルーガ ハラルド4、諸田 智克5、佐々木 晶6、薮田 ひかる7、中村 智樹8、大塚 勝仁9,1、石黒 正晃10、関口 朋彦11、浦川 聖太郎12、渡部 潤一13、伊藤 孝士13、大坪 貴文2、阿部 新助14、廣井 孝弘15、マーシャル ショーン16、小松 吾郎17,1、中村メッセンジャー 圭子18、小松 睦美19、紅山 仁5、橘 省吾5、三河内 岳5、野口 高明20、金田 英宏21、出村 裕英22、平田 成22、伊藤 元雄23、山口 亮24、松浦 周二25、巽 瑛理26、横田 康弘26、矢野 創26、吉川 真26、尾崎 直哉26、山本 高行26、豊田 裕之26、西山 和孝26、今村 裕志26、高島 健26 (1.千葉工業大学、2.産業医科大学、3.シュツットガルト大学、4.マックスプランク研究所、5.東京大学、6.大阪大学、7.広島大学、8.東北大学、9.東京流星観測網、10.ソウル大学、11.北海道教育大学、12.日本スペースガード協会、13.国立天文台、14.日本大学、15.ブラウン大学、16.セントラルフロリダ大学、17.ダヌンツィオ大学、18.ExLabs、19.埼玉県立大学、20.京都大学、21.名古屋大学、22.会津大学、23.海洋研究開発機構、24.国立極地研究所、25.関西学院大学、26.宇宙航空研究開発機構)
キーワード：
デスティニープラス、フェートン、フライバイ、宇宙塵、ふたご座流星群、活動的小惑星
DESTINY+ (Demonstration and Experiment of Space Technology for INterplanetary voYage with Phaethon fLyby and dUst Science) is an upcoming flyby mission to Asteroid (3200) Phaethon. Phaethon is the parent body of Geminid meteor shower and an active asteroid, recurrently ejecting dust during the perihelion passage at 0.14 au. It was previously planned to be launched in FY 2024 by a solid-fuel Epsilon S rocket and flyby to Phaethon in January, 2028 [8], but the launch is now scheduled in FY 2025. DESTINY+ is a joint mission of technology demonstration and science observation. For the science observation, high-speed (36 km/s) flyby imaging of Phaethon at the closest distance of 500±50 km is conducted with a tracking telescopic camera (TCAP) and a VIS-NIR multiband camera (MCAP) with four bands (425, 550, 700, and 850 nm). Direct measurement of dynamical and chemical properties of each dust particle is performed in the entire mission phase, including the Earth spiraling-out phase, the lunar swing-by phase, the interplanetary cruising phase and Phaethon flyby phase, with a dust analyzer (DDA). DDA is an impact-ionization dust detector and time-of-flight mass spectrometer, equipped with a two-axis gimbal. The preliminary design review (PDR) was complete in 2022 and currently in the critical design phase for the spacecraft bus system and science payloads. Functional tests and ground calibration activities using engineering models (EM) are currently underway for science instruments. Preliminary measurement of dust impact ionization TOF mass spectra with the DDA EM and the electrostatic accelerator installed at University of Stuttgart are on-going.
Imaging of Phaethon will be conducted autonomously during the high-speed flyby. Detailed understanding of its characteristics, especially the size, shape, albedo, and rotation state prior to the flyby is crucial for successful imaging. After the extensive ground-based observations of Phaethon during the close encounter in December, 2017 and observation campaigns for stellar occultation by Phaethon in 2019, there remain moderate uncertainty for the albedo, size and absolute magnitude. Continuing efforts of ground-based observation, including polarimetric observation [1], photometric observation [2], and stellar occultation observation [3] succeeded in better determining the albedo and size of Phaethon. The latest geometric albedo is Pv = 0.08–0.13 [1] and the absolute magnitude Hv= 14.23 ± 0.02 [2]. The latest shape model generated with a combination of the Arecibo radar data, multiple light curves from 1989 through 2022 and the stellar occultation observation outcomes in 2021 and 2022 in Japan shows that the maximum extent along each axis is 6.4 × 6.1× 5.1 km and volume-equivalent diameter is 5.2 km [4]. Another observation campaign is planned for stellar occultation by Phaethon in the western part of Japan on November 16 this year.
For operational planning upon the closest flyby of Phaethon, we plan to observe km-scale large concavities near the equator and low latitude regions identified by the Arecibo radar observation [5]. With the currently available rotation period (3.603957±0.000001 (hr)) [6,7], pole orientation [6, 7] and the updated 3D shape model of Phaethon [4], the flyby timing can be adjusted to be able to observe the targeted areas on the surface of Phaethon during the closest approach. The current observation targets are either the feature b (>1 km in size) on the southern hemisphere or the feature d (2 km in size) on the northern hemisphere [4].
[1] Geem, Ishiguro et al. (2022) MNRAS doi.org/10.1093/mnrasl/slac072.
[2] Beniyama, Sekiguchi et al. (2023) PASJ, doi.org/10.1093/pasj/psac109.
[3] Yoshida et al (2022) PASJ, doi.org/10.1093/pasj/psac096.
[4] Marshall et al (2023) DESTINY+ Science Working Team meeting 2023 abstract.
[5] Taylor P. A. et al. (2019) PSS 167,1.
[6] Kim M. -J. et al. (2018) A&A 619, A123.
[7] Hanuš J. et al. (2018) A&A 620, L8.
Imaging of Phaethon will be conducted autonomously during the high-speed flyby. Detailed understanding of its characteristics, especially the size, shape, albedo, and rotation state prior to the flyby is crucial for successful imaging. After the extensive ground-based observations of Phaethon during the close encounter in December, 2017 and observation campaigns for stellar occultation by Phaethon in 2019, there remain moderate uncertainty for the albedo, size and absolute magnitude. Continuing efforts of ground-based observation, including polarimetric observation [1], photometric observation [2], and stellar occultation observation [3] succeeded in better determining the albedo and size of Phaethon. The latest geometric albedo is Pv = 0.08–0.13 [1] and the absolute magnitude Hv= 14.23 ± 0.02 [2]. The latest shape model generated with a combination of the Arecibo radar data, multiple light curves from 1989 through 2022 and the stellar occultation observation outcomes in 2021 and 2022 in Japan shows that the maximum extent along each axis is 6.4 × 6.1× 5.1 km and volume-equivalent diameter is 5.2 km [4]. Another observation campaign is planned for stellar occultation by Phaethon in the western part of Japan on November 16 this year.
For operational planning upon the closest flyby of Phaethon, we plan to observe km-scale large concavities near the equator and low latitude regions identified by the Arecibo radar observation [5]. With the currently available rotation period (3.603957±0.000001 (hr)) [6,7], pole orientation [6, 7] and the updated 3D shape model of Phaethon [4], the flyby timing can be adjusted to be able to observe the targeted areas on the surface of Phaethon during the closest approach. The current observation targets are either the feature b (>1 km in size) on the southern hemisphere or the feature d (2 km in size) on the northern hemisphere [4].
[1] Geem, Ishiguro et al. (2022) MNRAS doi.org/10.1093/mnrasl/slac072.
[2] Beniyama, Sekiguchi et al. (2023) PASJ, doi.org/10.1093/pasj/psac109.
[3] Yoshida et al (2022) PASJ, doi.org/10.1093/pasj/psac096.
[4] Marshall et al (2023) DESTINY+ Science Working Team meeting 2023 abstract.
[5] Taylor P. A. et al. (2019) PSS 167,1.
[6] Kim M. -J. et al. (2018) A&A 619, A123.
[7] Hanuš J. et al. (2018) A&A 620, L8.