Asteroid (99942) Apophis is a potentially hazardous asteroid. The Korea Astronomy and Space Science Institute (KASI) recently proposed a rendezvous mission with Apophis, with a planned asteroid observation campaign to help determine the mission strategy in advance. In this study, we performed multicolor photometric observations of Apophis using the 1.0 m telescope at Kawabe Cosmic Park on 2021 March 10. The visible colors (g′, r′, and i′) of Apophis were obtained. The average colors of Apophis during our observations were as follows: g′ − r′ = 0.618 ± 0.021 and r′ − i′ = 0.180 ± 0.021. No significant color variation was observed in r′ − i′, but a slight variation may have occurred in g′ − r′ during the observation period of 4.63 hr. The obtained colors appeared to match those of an Sq-class asteroid, which is the asteroid type previously determined for Apophis by Binzel et al. (2009, Icarus, 200, 480) using the visible to near-infrared (0.55–2.45 μm) reflectance spectrum.

中文翻译：

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来自川部宇宙公园的潜在危险小行星 (99942) Apophis 的光度观测

小行星 (99942) Apophis 是一颗具有潜在危险的小行星。韩国天文和空间科学研究所（KASI）最近提出了与 Apophis 的会合任务，计划进行小行星观测活动，以帮助提前确定任务战略。在这项研究中，我们于 2021 年 3 月 10 日在川部宇宙公园使用 1.0 m 望远镜对 Apophis 进行了多色光度观测。获得了 Apophis 的可见颜色（g'、r'和 i'）。我们观察期间 Apophis 的平均颜色如下：g' - r' = 0.618 ± 0.021 和 r' - i' = 0.180 ± 0.021。在 r' - i' 中没有观察到显着的颜色变化，但在 4.63 小时的观察期内，g' - r' 可能发生了轻微的变化。获得的颜色似乎与 Sq 级小行星的颜色相匹配，这是 Binzel 等人先前确定的 Apophis 小行星类型。(2009, Icarus, 200, 480) 使用可见到近红外 (0.55–2.45 μm) 反射光谱。