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

小行星可以通过它们反射的光和它们发射的红外热辐射（热）来研究。研究人员已经开发出一种复杂的技术来研究接近地球的小行星（称为近地小行星，或NEAs）。他们将利用其热物理模型以及近地小行星的可见光和雷达观测来研究小行星的表面特性。虽然已知一些小行星具有光滑的表面，但其他小行星覆盖着厚厚的灰尘层，还有一些小行星具有每种类型的表面。这些不同的区域发射和反射辐射的方式不同，因此，在解释观测结果时，了解近地小天体表面的性质十分重要。研究人员将利用他们的热物理模型来解释近地小行星反射和发射的光，并将确定未来飞行任务的可能目标。应当指出，如果在与地球碰撞的轨道上发现近地小行星，了解近地小行星的性质对国家的国防至关重要。研究人员将让一名博士后和一名研究生参与外展活动，其中包括为K-12教师举办的四个研讨会。小行星的热模型揭示了许多关于它们表面特性的信息。简单的热模型往往不能自洽地拟合对同一小行星的多次观测。非球形和表面异质性都需要充分了解小行星。研究人员将使用多历元观测，并利用光学光变曲线和雷达数据的详细形状，利用多种观测几何形状来更真实地模拟热辐射，并更好地约束近地小行星的表面特性。他们将调查小行星表面的不均匀性、每个表面的粗糙程度、热惯性的重要性以及它如何随大小、光谱类型或旋转速率而变化;以及使用雷达导出的形状导出的热参数与使用光学光变曲线导出的热参数相比如何-该奖项反映了NSF的法定使命，并被认为是值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估的支持。

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.