论文标题
地球作为系外行星：I。使用空间解析的MODIS数据的时间变量热排放
Earth as an Exoplanet: I. Time variable thermal emission using spatially resolved MODIS data
论文作者
论文摘要
目前，地球仍然是一个可居住（和居住）世界的最好和唯一的例子。因此，重要的是要探索和理解地球的全部光谱特征和可变性，以便为未来的工具和任务的设计提供信息，并了解其诊断能力以及潜在的局限性。在这项工作中，我们使用Aqua卫星上的MODIS仪器收集的地球观察数据。完整的数据集包括3.66-14.40微米范围的15年热排放观测值（亚马逊雨林，南极洲，北极，北极，印度洋和撒哈拉沙漠）。然后，我们确定波长和表面类型的函数（即气候区和表面热特性）的变化，并研究是否可以检测到地球倾斜旋转轴的周期信号。我们的发现表明，（1）当对热发射数据进行分析时，观察几何形状起着重要的作用，因为地球的频谱的变化为三倍，取决于下面的主要表面类型。 （2）通常，来自二氧化碳（15微米）和臭氧（9.65微米）的强吸收带明显不那么明显，并且在极性区域的数据中部分缺乏，这意味着在这些情况下估计这些分子的正确丰富度水平可能会有挑战性； （3）时间分辨的热发射光谱编码有关季节/行星倾斜的信息，但其意义取决于观察几何和光谱带的考虑
For the time being, Earth remains the best and only example of a habitable (and inhabited) world. Therefore, it is important to explore and understand the full range of spectral signatures and variability of Earth in order to inform the design of future instruments and missions, and understand their diagnostic power as well as potential limitations. In this work we use Earth observation data collected by the MODIS instrument aboard the Aqua satellite. The complete data set comprises 15 years of thermal emission observations in the 3.66-14.40 microns range for five different locations on Earth (Amazon Rainforest, Antarctica, Arctic, Indian Ocean and the Sahara Desert). We then determine flux levels and variations as a function of wavelength and surface type (i.e. climate zone and surface thermal properties) and investigate whether periodic signals indicating Earth's tilted rotation axis can be detected. Our findings suggest that (1) viewing geometry plays an important role when thermal emission data is analyzed as Earth's spectrum varies by a factor of three and more depending on the dominant surface type underneath; (2) typically strong absorption bands from carbon dioxide (15 microns) and ozone (9.65 microns) are significantly less pronounced and partially absent in data from the polar regions implying that estimating correct abundance levels for these molecules might be challenging in these cases; (3) the time-resolved thermal emission spectrum encodes information about seasons/planetary obliquity, but the significance depends on the viewing geometry and spectral band considered
