Multicolor Photometry of Tiny Near-Earth Asteroid 2015 RN$_{35}$ Across a Wide Range of Phase Angles: Possible Mission Accessible A-type Asteroid

Abstract

Studying small near-Earth asteroids is important to understand their dynamical histories and origins as well as to mitigate the damage of the asteroid impact to the Earth. We report the results of multicolor photometry of the tiny near-Earth asteroid 2015 RN$_{35}$ using the 3.8 m Seimei telescope in Japan and the TRAPPIST-South telescope in Chile over 17 nights in 2022 December and 2023 January. We observed 2015 RN$_{35}$ across a wide range of phase angles from 2$^{\circ}$ to 30$^{\circ}$ in the $g$, $r$, $i$, and $z$ bands in the Pan-STARRS system. These lightcurves show that 2015 RN$_{35}$ is in a non-principal axis spin state with two characteristic periods of $1149.7\pm0.3$ s and $896.01\pm0.01$ s. We found that a slope of a visible spectrum of 2015 RN$_{35}$ is as red as asteroid (269) Justitia, one of the very red objects in the main belt, which indicates that 2015 RN$_{35}$ can be classified as an A- or Z-type asteroid. In conjunction with the shallow slope of the phase curve, we suppose that 2015 RN$_{35}$ is a high-albedo A-type asteroid. We demonstrated that surface properties of tiny asteroids could be well constrained by intensive observations across a wide range of phase angles. 2015 RN$_{35}$ is a possible mission accessible A-type near-Earth asteroid with a small $\Delta v$ of 11.801 km s$^{-1}$ in the launch window between 2030 and 2035.