Saturn's Atmospheric Structure through Infrared Spectroscopy

Nancy Chanover博士项目的目标是研究土星云层反射的太阳辐射和土星内部发射的热辐射之间的平衡。利用空间分辨光谱技术，该研究小组将获得一个独特的数据集，当与辐射传输和光谱合成建模相结合时，将完成以下测量目标：a)确定土星云不透明度的时空变化，b)确定土星化学成分的时空变化。这些测量将增强我们对土星大气过程的理解，包括它的动力学、化学成分和辐射转移。红外望远镜设施3.0米望远镜上的中分辨率和高分辨率红外光谱仪将用于获取土星2.5-5.4 m之间的光谱，这是一个对云不透明度和散射特性特别敏感的波长区域。土星的“冷点”可能控制着通过土星大气层的辐射传输，其方式类似于木星的5米“热点”，将作为纬度和倾斜路径几何的函数进行研究。这将阐明大气的详细垂直结构以及寒冷、黑暗区域在控制地球热辐射方面的作用。氨、磷化氢和乙烷在土星上的时空变化将作为理解土星大气动力学的一种手段进行研究。磷化氢（PH3）是一种不平衡物质，因此PH3的任何空间变化都可能与深层大气上升流的变化有关，而氨的变化则与云形成的空间变化有关。对乙烷（一种平流层分子）的全面研究将不同于在土星对流层中发现的氨。乙烷可以在3毫米附近检测到，这将为理解土星的大气垂直结构提供重要的约束。虽然土星反射率随纬度的变化比木星更微妙，但驱动这两颗行星循环的动力可能是相似的。因此，研究土星红外光谱的纬度变化关系到对土星大气能量平衡的认识。所有数据都将使用中心到边缘分析和光谱合成方法进行建模。通过这两种方法，目标是建立一个统一的土星大气结构模型，将气溶胶层置于适当的垂直水平，表征云和雾霾的不透明度和光学特性，推导氨、磷化氢和乙烷的混合比例，并量化上述量的时空变化。这项研究将对我们对土星大气层的理解做出独特的贡献。通过使用自一致的建模方法解释土星反射和热发射辐射的观测结果，该团队将对土星大气层中的能量平衡进行全面描述。利用空间分辨光谱的独特属性的观测方法将改进先前的研究。这些观测结果将与卡西尼号的可见光和红外测绘光谱仪（VIMS）的光谱覆盖范围重叠，并将补充与地面数据同时采集的高相位角航天器数据。它们还将探测比卡西尼号复合红外光谱仪（CIRS）更深的压力水平，因此将提供分子混合比研究的重要组成部分。这项工作是跨学科的，促进了新墨西哥州立大学（NMSU）迄今为止所进行的反射阳光分析与共同研究人员所擅长的热红外工作之间的协同作用。该项目将通过实际研究促进教学和培训，让几名新密歇根州立大学的学生参与到研究的各个方面。此外，它将扩大妇女和少数民族的参与，这两个群体在科学和工程领域的代表性不足

AST 0507558ChanoverThe objective of Dr. Nancy Chanover's project is to study the balance between reflected solar radiation atSaturn's cloud decks and emitted thermal radiation from Saturn's interior. Using a technique of spatially resolved spectroscopy, this research team will obtain a unique data set that, when coupled with radiativetransfer and spectral synthesis modeling, will accomplish the following measurement objectives: a)determine the spatial and temporal variation of Saturn's cloud opacity, and b) determine the spatial and temporal variation of Saturn's chemical composition. These measurements will enhance our understanding of Saturn's atmospheric processes, including its dynamics, chemical composition, and radiative transfer.The medium- and high-resolution infrared spectrometers at the Infrared Telescope Facility 3.0 meter telescope will be used to acquire spectra of Saturn between 2.5-5.4 m, which is a wavelength region particularly sensitive to cloud opacity and scattering properties. Saturn's "cold spots," which may control the radiative transfer through Saturn's atmosphere in a manner analogous to Jupiter's 5-m "hot spots", will be studied as a function of latitude and slant path geometry. This will elucidate the detailed vertical structure of the atmosphere and the role of the cold, dark regions in controlling the thermal emission from the planet. The spatial and temporal variations of ammonia, phosphine, and ethane on Saturn will be examined as a means of understanding Saturn's atmospheric dynamics. Phosphine (PH3) is a disequilibrium species, thus any spatial variation in PH3 may be linked to variations in upwelling from the deep atmosphere, whereas variations in ammonia would be associated with spatial variations in cloud formation. Center-to-limb studies of ethane, a stratospheric molecule, will differ from those of ammonia, which is found in Saturn's troposphere. Ethane can be detected near 3 mm, and will provide an important constraint for understanding Saturn's atmospheric vertical structure. While Saturn's reflectivity variations as a function of latitude are more subtle than those of Jupiter, the dynamics driving the circulation of the two planets may be similar. Thus, a study of the latitudinal variation in Saturn's infrared spectrum is relevant to the understanding of the energy balance of Saturn's atmosphere. All data will be modeled using both center-to-limb analyses and spectral synthesis methods. With these two approaches, the goal is to develop a unified model of Saturn's atmospheric structure that places aerosol layers at the appropriate vertical levels, characterizes cloud and haze opacities and optical properties, derives mixing ratios for ammonia, phosphine, and ethane, and quantifies the temporal and spatial variations of the above quantities. This study will make unique contributions to our understanding of Saturn's atmosphere. By interpreting observations of Saturn's reflected and thermally emitted radiation using a self-consistent modeling approach, the team will develop a comprehensive description of the energy balance in Saturn'satmosphere. Prior studies will be improved by using an observational approach that can exploit the unique attributes of spatially-resolved spectroscopy. The observations will overlap the spectral coverage of Cassini's Visible and Infrared Mapping Spectrometer (VIMS), and will complement the high phase angle spacecraft data taken contemporaneously with the ground-based data. They will also probe deeper pressure levels than Cassini's Composite Infrared Spectrograph (CIRS), and therefore will provide an essential component of molecular mixing ratio studies.This work is interdisciplinary and promotes synergy between the analysis of reflected sunlight that has been conducted at New Mexico State University (NMSU) to date and the thermal infrared work in which the Co-Investigators are experts. This program will promote teaching and training through practical research by involving several NMSU students and giving them opportunities to participate in all aspects of the research. In addition, it will broaden the participation of women and ethnic minorities, both underrepresented demographics in science and engineering fields.***