Peculiar Orbital Characteristics of Earth Quasi-Satellite 469219 Kamo‘oalewa: Implications for the Yarkovsky Detection and Orbital Uncertainty Propagation

Abstract

469219 Kamo‘oalewa is selected as one of the primary targets of Tianwen-2 mission, which is currently believed to be the most stable quasi-satellite of Earth. Here we derive a weak detection of the Yarkovsky effect for Kamo‘oalewa, giving A 2 = (−1.075 ± 0.447) × 10−13 au day−2, with the available ground-based optical observations from Minor Planet Center and a relatively conservative weighting scheme. Due to the quasi-satellite resonance with Earth, we show that the detection of the Yarkovsky effect by orbital fitting with astrometric observations becomes difficult, as its orbital drift shows a slow oscillatory growth resulting from the Yarkovsky effect. In addition, we extensively explore the characteristics of orbital uncertainty propagation and find that the positional uncertainty mainly arises from the geocentric radial direction in 2010–2020 and then concentrates in the heliocentric transverse direction in 2020–2030. Furthermore, the heliocentric transverse uncertainty is clearly monthly dependent, which can arrive at a minimum around January and a maximum around July as the orbit moves toward the leading and trailing edges, respectively, in 2025–2027. Finally, we investigate a long-term uncertainty propagation in the quasi-satellite regime, implying that the quasi-satellite resonance with Earth may play a crucial role in constraining the increase of uncertainty over time. Such an interesting feature further implies that the orbital precision of Kamo‘oalewa is relatively stable at its quasi-satellite phase, which may also be true for other quasi-satellites of Earth.