The Bulletin of The Korean Astronomical Society (천문학회보)
- Volume 46 Issue 2
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- Pages.57.4-58
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- 2021
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- 1226-2692(pISSN)
Rendezvous Mission to Apophis: III. Polarimetry of S-type: For A Better Understanding of Surficial Evolution
- Geem, Jooyeon (Seoul National University) ;
- Jeong, Minsup (Korea Astronomy and Space Science Institute) ;
- Jin, Sunho (Seoul National University) ;
- Sim, Chae Kyung (Korea Astronomy and Space Science Institute) ;
- Bach, Yoonsoo P. (Seoul National University) ;
- Ishiguro, Masateru (Seoul National University) ;
- Kwon, Yuna G. (Technische Universitat Braunschweig) ;
- Moon, Hong-Kyu (Korea Astronomy and Space Science Institute) ;
- Choi, Young-Jun (Korea Astronomy and Space Science Institute) ;
- Kim, Myung-Jin (Korea Astronomy and Space Science Institute)
- 김주연 (서울대학교) ;
- 정민섭 (한국천문연구원) ;
- 진선호 (서울대학교) ;
- 심채경 (한국천문연구원) ;
- 박윤수 (서울대학교) ;
- ;
- 권유나 ;
- 문홍규 (한국천문연구원) ;
- 최영준 (한국천문연구원) ;
- 김명진 (한국천문연구원)
- Published : 2021.10.13
Abstract
Asteroids have undergone various processes such as impacts, space weathering, and thermal evolution. Because they expose their surfaces to space without atmosphere, these evolutional processes have been recorded directly on their surfaces. The remote-sensing observations have been conducted to reveal these evolutional histories of the target asteroids. For example, crater and boulder distributions are unambiguous evidence for past nondestructive impacts with other celestial bodies. Multiband and spectroscopic observations have revealed space-weathering history (as well as compositions). Whereas most physical quantities have been examined intensively using spacecraft and telescopes, only a little has been studied on "the grain size". It is one of the fundamental physical quantities for diagnosing the collisional and thermal history of asteroids. Our group has conducted polarimetric research of asteroids (as well as Moon [1]) to determine the particle size and further investigate the evolutional histories of target asteroids [2],[3]. For example, the existence of regolith on an S-type asteroid, Toutatis, was suggested almost twenty years before space exploration [4]. Moreover, we reported that near-Sun asteroids indicate a signature of submillimeter grains, which could be created by a thermal sintering process by solar radiation [5]. However, it is important to note that in-situ polarimetry has not been reported on the asteroid surface, although the Korean Lunar Exploration Program aims to do polarimetry on the lunar surface [6]. Therefore, it is expected that the polarizer mounted on the Korean Apophis spacecraft can make the first estimate of the grain size and its regional variation over the Apophis surface. In this presentation, we outline research of S-type asteroid surfaces through remote-sensing observations and consider the role of polarimetry. Based on this review, we consider the purpose, potentiality, and strategy of the polarimetry using the onboard device for the Apophis spacecraft. We will report a possible polarization phase curve of Apophis estimated from ordinary chondrites and past observational data of S-type asteroids, taking account of the space weathering effect. Based on this estimation, we will consider the strategy of how to determine the particle size (and space weathering degree) of the Apophis surface. We will also mention the detectability of dust hovering on the surface.
Keywords