Near-Earth asteroids are not uniform: Using thermal models of multiple observations to reveal inhomogeneities

小行星既可以通过它们反射的光来研究，也可以通过它们发出的红外热辐射(热)来研究。研究人员开发了一种复杂的技术，用于研究接近地球的小行星(称为近地小行星，简称NEA)。他们将使用他们的热物理模型(TPM)，以及对近地小行星的可见光和雷达观测来调查小行星的表面特性。虽然有些小行星表面光滑，但有些小行星表面覆盖着厚厚的尘埃，还有一些小行星的表面各有不同的区域。这些不同的区域发射和反射的辐射是不同的，因此在解释观测结果时，了解NEA表面的性质是很重要的。调查人员将使用他们的热物理模型来解释近地天体反射和发射的光，并将为未来的飞行任务确定可能的目标。应该指出的是，如果在与地球相撞的过程中发现了近地天体，对近地天体的性质的了解将对保卫国家至关重要。调查人员将让一名博士后和一名研究生参加外联活动，其中将包括为K-12教师举办的四个讲习班。小行星的热模型揭示了许多关于它们表面属性的信息。简单的热模型往往不能自始至终地符合对同一小行星的多次观测。要完全理解一颗小行星，既需要非球形性，也需要表面异质性。研究人员将使用多历元观测，从光学光曲线和雷达数据中获得详细的形状，以利用多个观测几何图形来更真实地模拟近地天体的热发射，并更好地约束近地天体的表面属性。他们将调查小行星表面的不均一性；每个表面的粗糙程度，热惯性的重要性，以及它如何随大小、光谱类型或自转速度变化；以及使用雷达得出的形状与使用光学光曲线得出的形状的热参数如何比较。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Asteroids can be studied both by the light they reflect and by the infrared thermal radiation (heat) they emit. The investigators have developed a sophisticated technique for studying asteroids that make close approaches to the Earth (known as Near-Earth Asteroids, or NEAs). They will use their thermophysical model (TPM), together with visible and radar observations of NEAs to investigate the surface properties of the asteroids. While some asteroids are known to have smooth surfaces, others are covered with a thick layer of dust, and still others have regions of each type of surface. These different regions emit and reflect radiation differently, and thus it is important to know the nature of an NEA's surface when interpreting observations. The investigators will use their thermophysical model to interpret reflected and emitted light from NEAs and will identify possible targets for future missions. It should be noted that an understanding of the nature of NEAs would be vital to the defense of the nation should one be discovered on a collision course with Earth. The investigators will involve a postdoctoral student and a graduate student in outreach activities, which will include four workshops for K-12 teachers. Thermal modeling of asteroids reveals much about their surface properties. Simple thermal models often do not fit multiple observations of the same asteroid self-consistently. Both non-sphericity and surface heterogeneity are required to fully understand an asteroid. The investigators will use multi-epoch observations, with detailed shapes from optical lightcurves and radar data to leverage multiple observation geometries to model the thermal emission more realistically and better constrain the surface properties of NEAs. They will investigate such properties as the heterogeneity of the asteroid surfaces; the degree of roughness on each surface, the importance of thermal inertia and how it varies with size, spectral type, or rotation rate; and how derived thermal parameters using radar-derived shapes compare to those using optical lightcurve-derived shapes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.