CEDAR: A Robust Interferometer for Studies of Thermospheric Composition and Dynamics

CEDAR：用于研究热层组成和动力学的稳健干涉仪

• 批准号: 0535509
• 负责人: Steven Watchorn
• 金额: $ 17.56万
• 依托单位: Scientific Solutions Incorporated
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-12-15 至 2008-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0535509&HistoricalAwards=false
• 关键词: CEDAR; Robust; Interferometer; Studies; Thermospheric

The investigators will develop a procedure for measuring atomic oxygen concentrations in the upper atmosphere using ground-based observations of 844.6 nanometer Bowen fluorescence emissions, combined with incoherent scatter radar measurements and a numerical model. The neutral atmosphere plays a significant role in almost every thermospheric process, and oxygen is the dominant neutral species between 250 and 500 km. It is important in contexts ranging from thermospheric dynamics, to thermospheric-ionospheric interaction, to spacecraft operation. Yet, for the last two decades, determination of neutral oxygen density, [O], has relied heavily on semi-empirical atmospheric models like the Mass Spectrometer Incoherent Scatter (MSIS) theory, supported by 20-year-old satellite mass spectrometer data. While such methods are rather useful, their reliance on statistical averages leads to substantial uncertainties in their predictions, especially during variable phenomena such as magnetic storms. This study will measure atomic oxygen using a forward model and ground-based incoherent scatter radar and optical airglow measurements. The optical measurements will be made with a Spatial Heterodyne Spectrometer (SHS), which is a novel Fourier transform spectrometer that provides outstanding interferometric performance over a broad range of wavelengths without scanning. The SHS is like conventional interferometers (Michelson, Fabry- Perot), in that it is more compact with higher etendue at a given resolving power than grating spectrometers. However, being unscanned, it can be built far more robust than conventional interferometers, with relaxed flatness tolerances on critical optics. Moreover, unlike Michelsons, the SHS can be adjusted from one observation to the next so that the center of its transformed spectrum always falls near the science lines. A single SHS may thus produce easy-to-sample fringes in many wavelength regions. And, with a few other minor adjustments, one SHS can observe the airglow emissions mentioned above far more efficiently than a single Fabry-Perot system. It can also be used in an imaging mode. The same instrument can also measure other airglow emissions near 630, 732, and 1129 nanometer, providing even more information about crucial thermospheric processes and global winds.

研究人员将开发一种程序，利用地面观测844.6纳米波文荧光发射，结合非相干散射雷达测量和数值模型，测量高层大气中的原子氧浓度。中性大气几乎在每一个热层过程中都起着重要的作用，在250至500公里之间，氧是主要的中性物质。从热层动力学到热层-电离层相互作用，再到航天器操作，它都很重要。然而，在过去的二十年中，中性氧密度的测定[O]严重依赖于半经验大气模式，如由20年卫星质谱仪数据支持的质谱非相干散射（MSIS）理论。虽然这些方法相当有用，但它们对统计平均值的依赖导致其预测存在很大的不确定性，特别是在磁暴等可变现象期间。这项研究将使用正演模型和地面非相干散射雷达以及光学气辉测量来测量原子氧。光学测量将使用空间外差光谱仪（SHS）进行，SHS是一种新型傅立叶变换光谱仪，在宽波长范围内提供出色的干涉测量性能，而无需扫描。SHS就像传统的干涉仪（Michelson, Fabry- Perot），在给定的分辨能力下，它比光栅光谱仪更紧凑，具有更高的终端。然而，由于不需要扫描，它可以比传统干涉仪更坚固，在关键光学器件上具有宽松的平面公差。此外，与迈克尔逊不同的是，SHS可以从一次观测调整到下一次观测，因此其转换后的光谱中心总是落在科学线附近。因此，单个SHS可以在许多波长区域产生易于采样的条纹。而且，通过一些其他的小调整，一个SHS可以比一个单一的法布里-佩罗系统更有效地观察上述的气辉发射。它也可以在成像模式下使用。同样的仪器也可以测量630纳米、732纳米和1129纳米附近的其他气辉辐射，提供更多关于关键热层过程和全球风的信息。