CEDAR: Atmospheric Neutral Density Dynamics through Meteor Observations

该合同是一项实验性工作，旨在进一步开发一种新的测量技术，通过雷达观测流星轨迹来估计中性密度。当流星体进入地球大气层时，由于大气阻力，它们经历了减速，形成了雷达可以观测到的流星，提供了一个信息源，可以独立确定80至140公里高度的大气中性密度。在实验上测量这个区域的中性密度是非常具有挑战性的，而这项工作将通过使用一种新的技术来填补这一空白。了解中性密度是很重要的，因为低地球轨道卫星所经历的大气阻力与密度密切相关。描述这类流星体特征的数据的持续积累也将为航天器操作员和卫星数据的地面用户提供更好的风险评估。这项工作还将为新研究生提供研究课题，并将其成果纳入航空航天本科和研究生课程。通过在两个地理位置不同的雷达设施上同时进行流星雷达运动，并应用一种新的统计技术，从探测到的流星轨迹中得出中性密度值，将研究80至140公里高度的中间层-低热层区域中性密度的纬度和时间变化。将把这些大气中性密度测量值与现有的大气模式进行比较，以表征短期密度变化的来源，并评估它们与高层大气密度增强相耦合的程度。由此产生的总中性密度测量将补充温度、风、等离子体和单个金属种的测量，并为现有的稀疏或依赖于不同物理假设的中性密度测量提供另一种数据来源。该奖项反映了美国国家科学基金会的法定使命，并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，被认为值得支持。

This award is an experimental effort to further develop a new measurement technique for estimating neutral densities by using radar observations of meteor trajectories. As meteoroids enter the Earth's atmosphere, they experience deceleration due to atmospheric drag and form meteors that radar can observe, providing a source of information that can independently determine the neutral density of the atmosphere at altitudes of 80 to 140 km. Measurements of neutral densities in this region are very challenging experimentally and this work will fill this gap by using a novel technique. Knowledge of neutral densities is important since low-Earth-orbit satellites experience atmospheric drag that is strongly dependent on densities. The continued accumulation of data characterizing this meteoroid population would also provide improved risk assessment to spacecraft operators and to ground-based users of satellite data. This work will also provide research topics for new graduate students and results from this work will be incorporated into undergraduate and graduate courses in Aeronautics and Astronautics.The latitudinal and temporal variation of neutral density in the mesosphere-lower-thermosphere region between 80 and 140 km in altitude will be studied by conducting a simultaneous meteor radar campaign at two geographically distinct radar facilities and applying a novel statistical technique to derive neutral density values from the detected meteor trajectories. These measurements of atmospheric neutral density will be compared against existing atmospheric models to characterize the origins of short time density variations and to assess the extent that they will couple to density enhancements in the upper atmosphere. The resulting measurements of total neutral density will complement measurements of temperature, winds, plasma, and individual metallic species, and provides an alternative source of data to existing neutral density measurements that are sparse or that depend on different physical assumptions.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.