This work proposes a thermophysical model for realistic surface layers on airless small bodies (RSTPM) for the use of interpreting their multiepoch thermal light curves (e.g., WISE/NEOWISE). RSTPM considers the real orbital cycle, rotation cycle, rough surface, temperature-dependent thermal parameters, as well as contributions of sunlight reflection to observations. It is thus able to produce a precise temperature distribution and thermal emission of airless small bodies regarding the variations on orbital timescales. Details of the physics, mathematics, and numerical algorithms of RSTPM are presented. When used to interpret multiepoch thermal light curves by WISE/NEOWISE, RSTPM can give constraints on the spin orientation and surface physical properties, such as the mean thermal inertia or the mean size of dust grains, the roughness fraction, and the albedo via a radiometric procedure. As an application example, we apply this model to the main-belt object (24) Themis, the largest object of the Themis family, which is believed to be the source region of many main-belt comets. We find multiepoch (2010, 2014–2018) observations of Themis by WISE/NEOWISE, yielding 18 thermal light curves. By fitting these data with RSTPM, the best-fit spin orientation of Themis is derived to be (λ = 137, β = 59) in ecliptic coordinates, and the mean radius of dust grains on the surface is estimated to be μm, indicating that the surface thermal inertia varies from ∼3 Jm⁻² s^−0.5 K⁻¹ to ∼60 Jm⁻² s ^−0.5 K⁻¹ due to seasonal temperature variation. A more detailed analysis found that the thermal light curves of Themis show a weak feature that depends on the rotation phase, which is indicative of heterogeneous thermal properties or imperfections of the light-curve inversion shape model.

这项工作提出了一种用于无气小天体 (RSTPM) 上真实表面层的热物理模型，用于解释它们的多时期热光曲线（例如，WISE/NEOWISE）。RSTPM 考虑了真实的轨道周期、自转周期、粗糙表面、与温度相关的热参数，以及阳光反射对观测的贡献。因此，它能够产生关于轨道时间尺度变化的无空气小物体的精确温度分布和热辐射。介绍了 RSTPM 的物理、数学和数值算法的详细信息。当 WISE/NEOWISE 用于解释多时代热光曲线时，RSTPM 可以给出对自旋方向和表面物理特性的约束，例如平均热惯性或尘埃颗粒的平均尺寸、粗糙度分数、和通过辐射测量程序的反照率。作为应用示例，我们将此模型应用于主带天体 (24) Themis，Themis 家族中最大的天体，据信它是许多主带彗星的源区。我们发现 WISE/NEOWISE 对 Themis 的多期（2010 年，2014-2018 年）观测结果，产生了 18 条热光曲线。通过将这些数据与 RSTPM 拟合，可以推导出 Themis 的最佳自旋方向为（λ = 137, β = 59) 在黄道坐标中，表面尘埃颗粒的平均半径估计为 μ m，表明表面热惯性从∼3 Jm ^-2 s ^-0.5 K ^-1到∼ 60 Jm ^-2 s ^-0.5 K ^-1由于季节性温度变化。更详细的分析发现，Themis 的热光曲线显示出取决于旋转相位的弱特征，这表明热特性不均匀或光曲线反转形状模型存在缺陷。