Improved Meteoroid Characterization through Laboratory Experiments, Modeling, and Ground-based Observations

一项为期四年的研究旨在调查流星体的特性与由此产生的中间层和低热层流星光发射和雷达特征之间的关系，并增进对这种关系的了解。实验室实验将通过发射已知质量、速度和成分的射弹到一个含有已知密度气体的实验室中来模拟流星被地球大气层烧蚀的过程。所观察到的模拟流星的发光亮度与所用射弹的质量之间的关系将有助于利用地面雷达和光学流星测量来确定单个流星体的质量，而且准确度大大提高。然后，这一结果将量化对流星流入地球大气层的物体总数的估计。这项研究将通过在科罗拉多大学等离子体、大气和宇宙尘埃模拟研究所（IMPACT）设施进行的实验来完成，其目标是在明确的实验室条件下再现烧蚀过程。然后将这些实验结果应用于从雷达和光学技术获得的流星观测数据，以估计单个流星事件的质量，并验证实验和模拟结果。该奖项将进一步支持在CU博尔德攻读博士学位的研究生的教育和培训。此外，本科生将通过CU Boulder的发现学习学徒计划（Discovery Learning Apprenticeship Program）参与该计划。DLAP项目为CU本科生提供带薪的实践研究经验，最终生成最终研究报告并向该项目的教师和研究生进行演示。最后，研究结果将被纳入一个新的本科课程，题为“空间：环境和航天器”，开始2018年秋季。这门课程是在一个向所有专业的学生开放的校园范围内的“空间未成年人”的主持下开发的;因此，这门课程将触及科学和工程以外的学生。流星构成了空间环境的一个关键组成部分，因此这项研究将被用作一个关键课题，以强调近地空间环境的迷人复杂性。流星体进入地球大气层的速度在10至70公里/秒之间，质量从毫微微克到克或更大;然而，流星体的总质量通量仍然不确定，估计数的范围跨越两个数量级。流星体的消融被认为是造成高层大气金属层的原因，包括原子铁（Fe）、镁（Mg）、钙（Ca）、钾（K）和钠（Na）层，所有这些层的峰值都在85-95公里的高度范围内。这些金属层导致了各种各样的空气动力学现象，包括对流云颗粒的成核，海洋施肥与生物可利用的铁，并创建平流层气溶胶含量和O3化学之间的关系。此外，毫克级和更大的流星对绕地球轨道飞行的航天器构成风险，有可能造成物理或电气损害。准确评估总质量通量对于提高对这些领域的理解至关重要。总质量通量误差主要是由于无法确定单个观测粒子的质量造成的。造成流星体质量估计不准确的主要不确定性来源是将质量映射到可观测量的参数的不确定性，如光辐射和雷达截面。这些参数是发光效率和电离概率。该项目将有可能提供迄今为止对一系列速度和流星体代表性的不同材料的最佳测量。该奖项的首要科学目标解决了理解MLT高层大气学的一个简单而关键的问题：从太空进入我们大气层的总质量通量是多少？在实验室中创造人造流星的能力提供了一个很好的机会，以非专业人士可以理解的方式与社区进行互动。该奖项反映了NSF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。

A four-year research designs to investigate and improve the understanding of the relationship between the properties of a meteoroid and the resulting mesosphere and lower thermosphere (MLT) meteor optical emission and radar signatures. Laboratory experiments would be set up to simulate the ablation of meteors by the Earth's atmosphere by firing projectiles with known mass, speed, and composition into a laboratory chamber containing a known density of gas. The observed relationship found between the luminous brightness of the simulated meteor with the mass of the projectile used would help enable the use of ground-based radar and optical meteor measurements to determine the masses of individual meteoroids with considerably improved accuracy. This result would then quantify the estimate of the total meteor influx of objects into the Earth's atmosphere. This research would be done through experiments at the University of Colorado's Institute for Modeling Plasma, Atmospheres and Cosmic dusT (IMPACT) facility in which the goal would be the recreation of the ablation process in well-defined laboratory conditions. These experimental results would then be applied to meteor observational data derived from both radar and optical techniques, in order to estimate masses of individual meteor events and to validate experimental and modeling results. This award would further support the education and training of a graduate student pursuing a Ph.D at CU Boulder. In addition, undergraduate students would be involved in the program through the Discovery Learning Apprenticeship Program (DLAP) at CU Boulder. The DLAP program provides CU undergraduates a hands-on research experience, with pay, culminating in a final research report and a presentation to faculty and graduate students in the program. Finally, results from the research would be integrated into a new undergraduate course entitled 'Space: Environment and Effects', to begin in Fall 2018. This course is being developed under the auspices of a campus wide "Space Minor" open to students in all majors; as such, this curriculum would reach students beyond science and engineering. Meteors make up a key component of the space environment, and so this research would be used as a key topic to underline the fascinating complexity of the near-earth space environment. The researcher plans to include lectures on simulated meteor work in this series.Meteoroids enter the Earth's atmosphere with velocities between 10 and 70 km/s and masses from femtograms (fg) up to grams or larger; however, the total mass flux of meteoroids remains uncertain, with a range of estimates spanning two orders of magnitude. The ablation of meteoroids are suggested to be responsible for the creation of metal layers of the upper atmosphere, including atomic iron (Fe), magnesium (Mg), calcium (Ca), potassium (K), and sodium (Na) layers that all peak within the range of 85-95 km altitude. These metal layers lead into a variety of aeronomical phenomena, including the nucleation of noctilucent cloud particles, ocean fertilization with bio-available Fe, and creating a relationship between stratospheric aerosol content and O3 chemistry. Moreover, meteors of milligram size and larger pose a risk to spacecraft orbiting the Earth, with the potential to cause physical or electrical damage. Accurate assessment of the total mass flux is critical to improving the understanding of each of these areas. The total mass flux error is primarily caused by the inability to determine masses of individually observed particles. The major sources of uncertainty that lead to poor estimates of meteoroid masses are uncertainty in the parameters which map the mass to observables, such as optical emissions and radar cross section. These parameters are the luminous efficiency and the ionization probability. The project would possibly provide the best measurements to date for a range of velocities and for different materials representative of meteoroids. The foremost science objective in this award addresses a simple yet critical problem in understanding MLT aeronomy: what is the total mass flux entering our atmosphere from space? The ability to create artificial meteors in the lab provides a great opportunity to engage with the community in a way that non-specialists can understand.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.