Context. Near-Earth asteroid 162173 (1999 JU3) is a potential target of two asteroid sample return missions, not only because of its accessibility but also because of the first C-type asteroid for exploration missions. The lightcurve-related physical properties of this object were investigated during the 2011 - 2012 apparition. Aims. We aim to confirm the physical parameters useful for JAXA's Hayabusa 2 mission, such as rotational period, absolute magnitude, and phase function. Our data complement previous studies that did not cover low phase angles. Methods. With optical imagers and 1-2 m class telescopes, we acquired the photometric data at different phase angles. We independently derived the rotational lightcurve and the phase curve of the asteroid. Results. We have analyzed the lightcurve of 162173 (1999 JU3), and derived a synodic rotational period of 7.625 ± 0.003 h, the axis ratio a/b = 1.12. The absolute magnitude HR = 18.69 ± 0.07 mag and the phase slope of G = -0.09 ± 0.03 were also obtained based on the observations made during the 2011-2012 apparition. These physical properties are in good agreement with the previous results obtained during the 2007-2008 apparition.
Bibliographical noteFunding Information:
M.J.K. was partly supported by Korea Research Council of Fundamental Science & Technology. Y.J.C. was partly supported by the collaborative research project between NRF-JSPS (2012010270). Y.I.B. acknowledges the support of NRF grant 2011-0030875. This study was based in part on data collected at Subaru Telescope/Okayama Astrophysical Observatory/Kiso observatory (University of Tokyo) and obtained from the SMOKA, which is operated by the Astronomy Data Center, National Astronomical Observatory of Japan.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science