Investigation of Systematic Bias in Radiometric Diameter Determination of Near-Earth Asteroids: the Night Emission Simulated Thermal Model (NESTM)
Investigation of Systematic Bias in Radiometric Diameter Determination of Near-Earth Asteroids: the Night Emission Simulated Thermal Model (NESTM)
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近地小行星辐射直径测定系统偏差的研究：夜间发射模拟热模型 (NESTM)
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发表时间：
2009
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通讯作者：
S. Green
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作者：
S. Wolters;S. Green
近地小行星热模型（NEATM）已被证明是用于确定辐射直径的可靠的简单热模型。然而，NEATM 假设小行星夜间一侧的热辐射为零。我们通过测试具有不同热惯量 Γ 的模拟小行星表面产生的热红外通量的 NEATM，研究了这种假设如何影响最佳拟合的波束参数 η，高估了有效直径 Deff 并低估了大相位角下的反照率 pv。我们将 NEATM 与雷达直径进行比较，发现当 η 适合多波长观测时，NEATM 高估了直径，而当使用默认 η 时，NEATM 低估了直径。介绍了夜间排放模拟热模型（NESTM）。 NESTM 将夜侧温度 (Tnight) 建模为最大日侧温度（为 NEATM 计算的 Tmax，η= 1 ）的等纬度分数 (f)：Tnight=fTmax cos1/4φ ，其中 φ 是纬度。对于不同的热参数，可以找到 f 的范围，该范围取决于 Γ。将 NESTM 直径与 NEATM 和雷达直径进行比较，结果表明 NESTM 可以减少高估直径的系统偏差。当太阳相位角大于45°时，建议采用假定 Γ= 200 J m−2 s−1/2 K−1 的 NESTM 版本作为默认模型。
The near-Earth asteroid thermal model (NEATM) has proven to be a reliable simple thermal model for radiometric diameter determination. However, NEATM assumes zero thermal emission on the night side of an asteroid. We investigate how this assumption affects the best-fitting beaming parameter η, overestimates the effective diameter Deff and underestimates the albedo pv at large phase angles, by testing NEATM on thermal infrared fluxes generated from simulated asteroid surfaces with different thermal inertia Γ. We compare NEATM to radar diameters and find that NEATM overestimates the diameter when η is fitted to multiwavelength observations and underestimates the diameter when default η is used. The night emission simulated thermal model (NESTM) is introduced. NESTM models the night side temperature (Tnight) as an iso-latitudinal fraction (f) of the maximum day side temperature (Tmax calculated for NEATM with η= 1 ): Tnight=fTmax cos1/4φ , where φ is the latitude. A range of f is found for different thermal parameters, which depend on Γ. NESTM diameters are compared with NEATM and radar diameters, and it is shown that NESTM may reduce the systematic bias in overestimating diameters. It is suggested that a version of the NESTM which assumes Γ= 200 J m−2 s−1/2 K−1 is adopted as a default model when the solar phase angle is greater than 45°.